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3-Dimensional numerical modelling of geocell reinforced sand beds
... It comprises of polymeric sheets such as high-density polyethylene interconnected in a cellular fashion to form a 3-D geosynthetic product, providing all round confinement to the soils. Geocells formed using different materials [23][24][25] such as geotextile, geogrid, papers and bamboo have been used by many researchers in the past [16,[26][27][28][29][30][31][32][33][34][35][36]. It has been observed that the soil beds if reinforced with geocells can increase the bearing capacity of composite system very effectively. ...
... Thereafter, it is extracted from AutoCAD with extension (.dxf) through "import" feature available in structures mode of PLAXIS 3D . The extracted polycurves are then extruded in Z-direction with the required height of geocell as shown in Fig. 2. The properties of geocell-geogrid reinforced sand bed over stone column in layered soil have been adopted from the reported value in Hegde and Sitharam [32] and are presented in Table 4. The axial stiffness values are calculated by multiplying Young's modulus and thickness of geosynthetics adopted, while shear stiffness value is calculated using the expression adopted from Choudhary and Dash [54]. ...
... Similarly the numerical model consisting of geocell-geogrid reinforced sand bed was validated against the experimental results of Hegde and Sitharam [32]. Model dimension and material properties were kept identical to the original experimental work. ...
In the present study, a series of three-dimensional numerical analysis has been performed to understand the behaviour of stone column in layered soil and the purpose of using geocell–geogrid as reinforcement in improving the overall performance of the composite system. Results indicate that the performance improvement visibly enhances with an increase in the depth of top layer (H/D) of clay beds. However, the performance improvement is found to be insignificant beyond the depth of top layer equal to 4D. With the provision of geocell–geogrid reinforcement over the top of stone column, the percentage increase in the bearing capacity of encased stone column in layered soil was found to be nearly 166%. Also, the overall increase in load carrying capacity of reinforced composite system was found to be more than 8 times than that of layered clay beds without stone column. Hence, it clearly indicates that the performance of layered clay beds can be improved very effectively with the provision of geocell–geogrid reinforced sand beds over the stone column placed in layered soil system. Further, the load carrying capacity of stone column is greatly influenced by the friction angle of stone aggregates, stiffness of geosynthetics material and the pocket size of geocell.
... Parallel to the advancements in piled raft foundations, geocell reinforcement (GR) has emerged as a groundbreaking solution to the perennial challenges of soil instability [14][15]. Characterized by their distinctive three-dimensional honeycomb structure, geocells have demonstrated a remarkable capacity to enhance the strength and modulus of non-cohesive soils, such as sand and gravel. ...
... The geocell material properties, sourced from [14], are represented as elastic materials in the model. This simplification is made to reduce computational costs and alleviate numerical complexities. ...
... Firat Univ Jour. of Exp. and Comp. Eng., 3(1), [11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27]2024 M. Pourgholamali, F. Asghapour ...
The effect of geocell-reinforced cushion on load distribution and settlement reduction in unconnected piled raft foundations was investigated. Modeling and analysis of various scenarios were carried out using Abaqus software. In this research, a total of nine models, including one connected, three unconnected and unreinforced, and five unconnected and reinforced with geocell, were analyzed. Cushions with thicknesses half of, equal to, and twice that of the foundation were used. The results have shown that optimal outcomes in terms of load distribution efficiency and settlement reduction are achieved when the cushion's stiffness is set at half that of the foundation. The obtained results demonstrate the positive effect of geocell reinforcement in enhancing the performance of unconnected piled raft foundations. The introduction of geocells into the models increases soil stiffness and pile load ratio, consequently enhancing the load-bearing capacity of the piled raft foundation compared to the unreinforced models. The study's findings pave the way for a more effective use of geocells in civil engineering applications, particularly in scenarios demanding high load-bearing capacity and minimal foundation settlement.
... The length and the number of the reinforcement layers have a positive effect on soil improvement level [18]. Furthermore, geocell material produced in a friction-increasing structure gives better performance compared to smooth surface geocell material [23]. It was concluded that the reinforcement method using geocell is more effective than other types of geosynthetics, due not only to transferring the foundation load into deeper points, but by also reducing the observed stress and deformation characteristics as well as improving the effectiveness of vibration mitigation [7,[24][25][26]. ...
... First of all, the soil volume was drawn with dimensions of 1.5m x 1.5m x 1.3m according to the experimental soil box. The linear elastic-perfect plastic Mohr-Coulomb model, which is suitable for subbase application and can analyze faster than other material models, was used to simulate the silty sand type (SM) of natural subgrade layer and well graded gravel type of (GW) stabilized base layer [23,62]. The sections were studied under undrained conditions as they contain clay content in a closed experimental cell. ...
... The axial stiffness of the geocell was calculated with respect to the tensile strength corresponding to 2.5% elongation according to the manufacturer parameters (Table 5), although geotextile elongation at break was determined from the tensile strength at a minimum 50% elongation [54]. As in the use of geocells with high axial stiffness, which is another aim of this study, this parameter can be found in the literature from 340 kN/m to 465 kN/m for high density polyethylene geocells [23,72,73]. elements and fine mesh were used, even though a medium mesh was used in the remaining parts of soil ( Fig. 4(b)). ...
Depending on the project traffic, the total thickness of a granular base can reach excessive values. Granular layers of large thicknesses undoubtedly extend the duration of a project and cause high project total costs. In this study, the improvement in settlement behaviour of unbound granular base layers reinforced with geocell was investigated by way of large-scale laboratory tests and finite element modeling. Plate loading tests were performed on unreinforced and geocell reinforced base layers, which were constructed on subgrade soil with a low bearing capacity under 1750 kPa overload condition. It was determined that the amount of settlement observed at the same stress levels decreased with an increase in the aperture size from 440 mm to 660 mm and the geocell height from 100 mm to 150 mm. The reduction in settlement potential, which reached 78% compared to the unreinforced reference section around 25 kPa, decreased to 55% at around a 200 kPa standard load. With an increase in the vertical stress level, the effectiveness of geocell reinforcement decreases and a serious decrease occurs after 500 kPa, becoming completely unserviceable when a level of 1000 kPa is to be exceeded. Although the difference between the experimental results and the modeling values remained below 5% in the reference section, it reached as high as 30% differences in the geocell implemented sections up to 200 kPa, due to three-dimensional geocell adaptation problems within the finite element calculations. In this way, it will be possible to increase the performance of road surfaces by keeping the pavement thickness constant, and also it will be possible to design more economical sections by reducing the required thickness.
... This type of confinement greatly improves the shear strength of the granular soil leading to an enhanced bearing capacity of the system. Several investigators used 3D cells that were prepared in the laboratory using materials like geotextile, geogrid, papers, and bamboo (Bush et al., 1990;Krishnaswamy et al., 2000;Dash et al., 2001;Dash et al., 2003;Chen & Chiu, 2008;Latha & Somwanshi, 2009;Hegde & Sitharam, 2014;Hegde & Sitharam, 2015;Hegde & Sitharam, 2017;Dash & Choudhary., 2018;Choudhary et al., 2019;Arvin et al., 2022). It was reported that the performance of soil beds can be greatly enhanced by providing a layer of geocell reinforcement within the course of the soil mass. ...
... As per the assessment of the literature, it seems that geocell is modelled either as the equivalent composite approach (Hegde & Sitharam, 2014;Song et al., 2017;Halder & Chakraborty, 2020) or as a square box shape (Song et al., 2018). In the equivalent composite approach, the geocell-soil composite is assumed as a soil layer with better strength and stiffness. ...
... On the other hand, the honeycomb structure of the geocell effectively mitigates this issue by distributing the stresses uniformly along the entire periphery. As a result, this uniform distribution ensures a more precise and accurate outcome (Hegde & Sitharam, 2014). In order to get an accurate performance of the system, it is essential to study the behaviour of the geocell-reinforced retaining wall considering the actual curvature of the expanded geocell. ...
The demand for geocell-reinforced retaining walls has increased due to the rising requirements of infrastructural development and constraints in land use. The cumbersome geometry of geocell poses challenges when it comes to numerical modelling. In this study, the geocell-reinforced retaining walls have been modelled using 3D finite element method to investigate the behaviour of the retaining wall by introducing multiple layers of actual honeycomb-shaped geocell mattresses. The result indicates that the provision of reinforcement significantly increases the stability of the retaining wall system. The lateral deformation in the retaining wall increases with an increase in both surcharge load and the wall’s facing angle. The factor of safety was found to decrease by nearly 1.75 times with an increase in the wall’s facing angle from 50 to 80°. With an increase in the height of the geocell mattress from 125 to 250 mm, a significant reduction in lateral displacement was observed. However, further increase in the height of the geocell mattress shows marginal effect on the performance of the composite wall system. Besides, the proposed model shows encouraging agreement with the experimental results indicating that the present model can be used to study the behaviour geocell reinforcement retaining wall system.
... When modeled as square or cylindrical shapes, the applied stresses over the walls of the geocell are not distributed evenly, which is a limitation of this modeling approach. However, the analysis was conducted for a geocell-reinforced foundation system by simulating the real curved honeycomb shape of the geocell (Hegde and Sitharam 2015b;Biabani et al. 2016;Gedela and Karpurapu 2021). ...
... Therefore, the results revealed that the smaller pocket size in the geocell was more effective compared with the large pocket size of the geocell when increasing the bearing capacity. A similar observation was reported in the literature (Dash et al. 2001b;Hegde and Sitharam 2015b). ...
... In the geocell-reinforced foundation bed, the stresses were distributed in the lateral direction, and the interlinked pocket of the geocell acted like a semirigid slab to distribute the applied load over a larger area, which resulted in improving the performance of the foundation bed. A similar observation was reported in the literature (Hegde and Sitharam 2015b;Ari and Misir 2021). The stress contour in Fig. 14 shows that the stress distribution for C&D waste was smaller than aggregates and sand due to the higher friction values between the particles. ...
... Furthermore, the complexity of the interactions and their properties even makes it difficult and requires immense computational power and time. Geocell as reinforcement caught many researchers attention [1,2,[4][5][6][7][8][9][10][11] and their findings incriminated efficacy of geocell in improving soil properties [3] Performed analytical and numerical investigations of block resonance tests to study the dynamic response of soil under vertical dynamic excitation. ...
... Three soil types are used: silty, loose, and dense sand. These materials are similar to [6]. Silty sand is classified as SP, poorly graded sand with a specific gravity of 2.64, uniformity coefficient (Cu) of 3.08, curvature coefficient (Cc) of 1.05, and maximum and minimum void ratios of 0.81 and 0.51. ...
... The geocell, with its intricate three-dimensional honeycomb-like structure crafted from interconnected synthetic strips, serves as a robust solution for reinforcing foundations [1]. Within this structure, soil experiences heightened lateral stresses, effectively limiting the movement of soil particles and enhancing shear strength. ...
... Easy handling and installation ensure optimal geocell performance. These advantages are supported by various studies [1,3,5]. Therefore, sand was tested for using IPGC in the experimental study [12] and was also used to verify our calculation results in this study. ...
This paper develops an analytical model to calculate the ultimate bearing capacity of the integrated plug high-strength geocell (IPGC)-reinforced foundation under a square footing. The high strength and stiffness of the geocell wall and the typical failure of the integrated plug-in joint tearing were considered. The ultimate bearing capacity of the IPGC-reinforced foundation was calculated in two separate parts. The ultimate bearing capacity of an unreinforced foundation was calculated using the modified Terzaghi equation. The increased bearing capacity of the IPGC was calculated as the function of the tearing force of the geocell wall, the height and the diameter of a geocell, the empirical static earth pressure coefficient, and the vertical additional stress coefficient under uniformly distributed rectangular loading. The results showed that the maximum error between the experimental and the theoretical results is less than 18%. The ultimate bearing capacity of IPGC-reinforced foundations decreases with larger geocell diameters. When the diameter of the geocell exceeds 1.8 times the foundation width, the confinement effect of IPGC becomes negligible. The findings of this study offer a robust analytical equation for predicting IPGC-reinforced foundations, along with valuable insights into the efficacy of IPGC reinforcement in enhancing foundation stability.
... Continuum-based methods, such as the finite element method (FEM) and finite difference method (FDM) (Jirawattanasomkul et al., 2018(Jirawattanasomkul et al., , 2019, soils are modeled using solid element. Similarly, the geocell can also be modeled by solid element Ling, 2013a, 2013b;Biabani et al., 2016;Arias et al., 2020;Nayyar and Sahu, 2021) or simplified planar structural elements (Hegde and Sitharam, 2015a;Satyal et al., 2018;Ari and Misir, 2021;Gedela and Karpurapu, 2021;. These methods excel in simulating large-scale models efficiently but do not fully capture the granular nature of soil (Grange and Salciarini, 2022). ...
... This suggests that the presence of multiple smaller-sized cells imparts stronger constraints compared to a single larger-sized cell. This observation concurs with the outcomes of prior experimental studies conducted by Pokharel et al. (2010), Hegde and Sitharam (2015a), and Dash (2020). ...
Size-related factors, such as the dimensions and cell count of geocell, play a crucial role in determining the effectiveness of soil reinforcement. In this study, a 3D coupled framework that leverages the strengths of both continuum and discontinuum methods was developed to investigate the influence of pocket size and multi-cell configuration on geocell-reinforced soils. To unveil the impact of size-related factors on soil-geocell interactions , reinforced soils containing various geocell configurations (single large-sized cell, multiple small-sized cells), as well as geocell-free soils subjected to increasing levels of confining pressure were extensively examined. This thorough investigation aimed to establish correlations between macroscopic responses and underlying micromechanical mechanisms. Our findings revealed that the presence of the geocell not only enhances the densification of interparticle contacts and reduces the number of floating particles that contribute minimally to load support, but also facilitates the concentration of force chains within the geocell structure. This leads to an increase in elastic stiffness along the loading axis. These observations highlight that the geocell's confining mechanism enhances both the load-carrying capacity and the infill rigidity, thereby preventing lateral soil spreading. In essence, the geocell serves to increase the soil's ability to withstand load and maintain its structural integrity laterally.
... The reinforcement used in the analysis was simulated using the Geogrid structural element, a linearly elastic material with no failure limit. Although past studies have pointed out that geogrid is a load, temperature, and time-dependent material (Huang et al. 2009), the elastic constitutive model has been used by researchers for modeling geogrid-reinforced foundations (Hegde and Sitharam 2015;Choudhary et al. 2019b) because of the simplicity of the model. The Geogrid element can interact with the grid through interface elements. ...
... The soil-geogrid and soil-anchor interface properties used in the analysis were calculated using the following expressions: c i = 0.67 × c and tan(ϕ i ) = 0.67 × tan(ϕ) (Yu et al. 2015, where c i and ϕ i are the interface cohesion and friction angle, respectively, and c and ϕ are the cohesion and internal friction angle of the soil, respectively. The shear stiffness of the soil-geogrid interface (k i ) was chosen to be 2.36 MPa/m, which has been used by previous researchers (Hegde and Sitharam 2015;Choudhary et al. 2019b). ...
The present study pertains to the probabilistic assessment for analysis and design of uplift capacity of transmission tower foundation reinforced with horizontal anchor using the radial basis function (RBF)-based response surface method. The deterministic uplift capacities of horizontal anchors in both unreinforced and reinforced soils were obtained using a finite difference numerical scheme. For the case of reinforced soil, geogrid was used and placed on top of the anchor plate. The improvement in uplift capacity due to the inclusion of geogrid reinforcement is first discussed. Next, RBF-based response surface models were constructed using the observed uplift resistance from the deterministic numerical model. The reliability of the foundation subjected to uplift forces was assessed using the Monte Carlo simulation, considering uncertainties of the soil and geogrid properties. The influence of safety factors on the failure probability of the foundation for both unreinforced and reinforced cases was shown. Variation of the probability of failure with different coefficients of variation of input variables was also investigated. The reinforcement stiffness was the most influencing parameter, having a pronounced effect on the failure probability of the reinforced foundation. Significant improvement in the uplift capacity and reduction in failure probability of the foundation were observed when a reinforced anchor was used, showing the effectiveness of reinforcement on top of the anchor plate. The results indicated that for the same failure probability, the reinforced anchors require much lower depth compared to unreinforced anchors.
... (3) the reference case; and (4) an actual shape of geocell is utilized in this analysis. Hegde and Sitharam [31] and Yang et al. [32] performed experimental studies and compared the load-settlement behavior of the geocell with that of the corresponding simulated models to prove the competence of Plaxis 3D in the simulation of the geocell. Autodesk Auto-CAD 2021 program was used to build the surface of the geocell, which was afterwards imported into Plaxis 3D. ...
... (3) the reference case; and (4) an actual shape of geocell is utilized in this analysis. Hegde and Sitharam [31] and Yang et al. [32] performed experimental studies and compared the load-settlement behavior of the geocell with that of the corresponding simulated models to prove the competence of Plaxis 3D in the simulation of the geocell. Autodesk AutoCAD 2021 program was used to build the surface of the geocell, which was afterwards imported into Plaxis 3D. ...
This research focuses on advancing the geosynthetic-reinforced pile-supported embankment technology over loose sandy soil. A small-scale laboratory model supported by floating piles and a geotextile layer was constructed, and a numerical model was validated against laboratory measurements. This study aims to achieve a more uniform distribution of the load over all piles of the system via a parametric study that analyzes the influence of embankment fill material, horizontal reinforcement scenarios, pile cap shape, and pile type. The results demonstrate that using embankment fill with high cohesion and internal friction properties leads to a significant reduction of 46% and 37% in maximum settlements, respectively, and similarly, results in a noteworthy reduction of 48% and 50% in differential settlements. The incorporation of two geotextile layers contributes to a reduction of up to 30% in maximum settlement. The utilization of plus-shaped caps in small areas, with an area equal to three times the cross-sectional area of the pile, has been substantiated as the preeminent approach for the reduction of settlements. Piles with caps also present better behavior regarding differential settlements compared to longer piles and piles with bigger diameters under the same volume condition.
... Since the pocket size of the geocells is inversely proportional to the confining stresses developed in the infill soil, the decrease in the pocket size of geocells increases the additional confining stresses offered by the cells per unit volume of the soil, increasing the apparent cohesion [8,27,35,38]. Thus, the infill soil gets restrained within the geocell pockets due to increased confining stress, leading to controlled settlements and heaves in geocellreinforced structures [7,22,27]. ...
... Studies showed a greater improvement in geocell performance with rough surfaces [11,17,38]. The increase in the roughness of geocell walls increases the angle of interface friction between the cell walls and the infill soil. ...
Geocells, which are polymeric interconnected cells filled with soil, provide excellent support to loads through all-round confinement and a beam effect; hence, they are extensively used in various geotechnical applications such as embankments, foundations, pavements, slopes, railways, and reinforced earth (RE) walls. Although the applications of geocells are studied extensively, their geometric and parametric evolution as a stable support to heavy loads receive less attention. The current versatile configuration of geocells has geometrically evolved after accounting for all the factors that give them optimum reinforcement efficiency. This paper presents a state-of-the-art review of the geometric evolution of geocells in the context of transportation geotechnical engineering. Effects of shape, size, stiffness, and surface roughness of geocells, and properties of infill and native soils on the performance of geocells are compiled from the literature to get important design insights. The application of geocells in pavements is discussed, concluding that geocells improve the cyclic load carrying capacity and resilient characteristics of pavement, reduce rut depths, and increase traffic benefit ratio (TBR). Hence, geocells can be a sustainable alternative to natural materials in transportation infrastructure, with the added advantages of reduced carbon footprint and maintenance costs.
... In practical scenario, the optimum reinforcement configurations may not be feasible to provide during field implementation owing to space constraints. Accordingly, researchers have provided alternative options to improve bearing capacity as well as to minimize the settlement of the footing by applying thick sand pad, mono piles, electro-osmosis and geocell layers (Adams and Collin 1997;Biswas et al. 2016;Hegde and Sitharam 2015;Li et al. 2017;Bjerrum et al. 1967). However, these remediation methods are costlier than the option of reinforcing of ground using geosynthetic layers. ...
The present study aims at providing design guideline for surface strip footing resting on soil mass encapsulated with geosynthetic reinforcement. The guideline has been provided based on extensive finite element based numerical analysis conducted on loose, medium dense and dense sandy soil. The width of the strip footing (B) and the distance between bottom of the footing and top horizontal reinforcement layer (u) have been kept constant in the analysis. However, the distance between two horizontal reinforcement layers (h) and length of the encapsulated reinforcement layer (l) have been varied to understand the effect of influencing parameters on the pressure-settlement behaviour of reinforced soil mass. Based on the maximum normalized bearing pressure, the optimum reinforcement configuration has been found at l/B=2 and h/B=0.6. A multiple linear regression equation based on numerical analysis data has been developed to evaluate the normalized bearing pressure of reinforced soil mass at different settlement ratio of footing. The developed equation has also been compared with the published literature related to experimental investigations and numerical studies. The statistical analysis of model test data reveal that the magnitude of normalized bearing pressure depends primarily on angle of internal friction of soil mass and settlement ratio of the strip footing.
... In this study, the properties of sand are taken from studies [21]. Moreover, Young's modulus of elasticity and Poisson ratio of sand are taken from the studies [22]. The properties of clay soil is also taken from the studies [23]. ...
In this study, geothermal energy has demonstrated significant potential as a sustainable and renewable energy resource for space conditioning. However, developing nations like India have not yet adopted this technology for space heating and cooling, despite experiencing satisfactory seasonal variation in ambient temperatures in many places. Furthermore, the thermo-mechanical behavior of geothermal energy piles in the specific soil and climatic conditions of the area has not been investigated. The present study aims to numerically explore the thermo-mechanical response of a geothermal energy pile in the local soil under the climatic conditions of Jamshedpur, a city in Eastern India. The study analyzed the shear stress at the interface of the pile and adjacent soil, the displacement of the pile head, middle, and toe, and the volumetric strain of the soil. The results of this study was validated and compared with previous studies and found a good agreement with it. The maximum displacement for mechanical loading was observed to be 16 mm in sand and 11.4 mm in layered soil, respectively, for an L/d ratio of 15. Under thermo-mechanical loading, the change in displacement was 0.7 mm in sand and 0.4 mm in layered soil. The maximum shear stress was developed at the toe, reaching 60 kN/m 2 for L/d = 15. The obtained results reveal an encouraging outcome and help in gaining confidence in constructing geothermal energy piles.
... PLAXIS 3D is a three-dimensional finite element analysis application that analyses the deformation and stability of various geotechnical situations [7]. Soil models can be created in two modes: soil mode and structure mode. ...
This paper discusses to develop a three dimensional (3D) numerical model which can effectively simulate the behavior of geocell reinforced soils using a commercial finite element program. In the usual instance, numerical modeling of geocell is difficult due to their curved geometry and complex material surfaces. It is therefore not surprising that much of the previous studies on geocell have eluded this approach and have otherwise used an equivalent composite method. It treats the geocell–soil composites as a new soil layer with improved strength and stiffness properties. Unfortunately, despite its simplicity, this method can often be incorrect as it does not properly account for the state of in situ stress in the soils. Plane stress conditions are also violated especially when the geocell are placed close to the ground surface. Likewise, the shape of the geocells also affect the working of geocell. In the present study, the reinforced soil layer considers the interaction between the geocell and its nodes at connections. Geocell are modelled using poly-curves available in the software. Three types of simulations are then made, they are: reinforced soil with geocell and unreinforced soil, rectangular geocell with curvilinear geocell, and geocell with different axial stiffness. It was seen that the secant modulus of the reinforced soils increases with the increase in the curvature of the geocell. And as the axial stiffness of the geocell material increases, the secant modulus of the reinforced soil also improves.
... These commercial geocells come with prefixed dimensions and textures, which cannot be customized easily. Most of the published studies on model studies using geocell reinforcement used prototype geocells, irrespective of the geometric scaling used in the models [6][7][8]. The reason for not scaling down the tensile strength of the geocells is the non-availability of low-strength geocells in the market. ...
Geocells are being extensively used in road and rail embankments, pavements and retaining structures. Research on the cyclic load performance of these structures is heavily based on reduced scale model tests coupled with numerical modelling. Most of the available model studies on geocell-reinforced structures use prototype geocells or geocells made using nonwoven geotextiles or geonets due to the unavailability of low strength geocells in the market. Such studies suffer from many limitations that arise due to discrepancies in geometric scaling, texture and mechanical response. Hence, 3D printing, which enables the manufacturing of geosynthetics with optimized configurations, customized texture and mechanical properties holds great promise in producing low strength geocells for reduced scale model tests. This study demonstrates the applicability of 3D printing technique for manufacturing customized geocells using polypropylene (PP) sheets. Wide-width tension tests, junction strength tests and interface shear tests were carried out on 3D printed geocells. Through these tests combined with PIV analysis, it is shown that the geocells fabricated by ultrasonically welding the 3D printed polypropylene sheets could closely replicate the tensile and interface shear behaviour of the commercial geocells.
... Now, in order to represent the behaviour of the geocell layer, it has been modelled using the linear-elastic model. Numerous studies [26,[45][46][47][48][49][50] have reported that geocell layers undergo strains within the elastic range under loading conditions. The input value for the material properties of the geocell layer is the axial stiffness (EA) of 190.4 kN/m. ...
This study aims to comprehensively analyse the behaviour of geocell-reinforced pavement and discern the key factors affecting its performance through a combined approach of experimental and numerical analyses. It begins with full-scale model testing of reinforced and unreinforced sections, followed by numerical analysis conducted using the three-dimensional finite element program PLAXIS 3D. The numerical models were calibrated against the results obtained from the experimental study. The numerical investigation primarily focuses on evaluating how different parameters, including base material, diameter of wheel contact area, and subgrade conditions, impact the performance of geocell-reinforced pavement sections. The incorporation of geocells in the base layer has shown a marked reduction in both permanent deformation and concentration of subgrade pressure compared to unreinforced sections across all pavement sections. The rut depth reduction value is found to be influenced by the subgrade strength and the diameter of the wheel contact area. However, the study highlights a more significant decrease in rut depth and subgrade vertical stress in reinforced pavement sections constructed with a base material of fly ash compared to the sections with bases made of wet mix macadam (WMM) and sand materials. The study emphasizes fly ash as an optimal infill material choice, demonstrating minimal rut depth and lower pressure values at the subgrade level.
... According to the literature, for a single isolated footing over GRS, the influencing parameters considered for statistical analysis are geocell height (h), sand cover thickness (u), geocell aperture size (d ), and free space between two footings (c) [ Fig. 2(b)]. Changing these parameters can leads to significant variation in the bearing pressure of footings on geocell-reinforced soils (Hegde and Sitharam 2015b). Past investigations show that smaller aperture size and greater height for geocell reinforcement placed at optimum embedment depth leads to greater efficiency and load-carrying Table 3 indicates the dimensionless form of parameters with their values, all of which are normalized by D. These variables have five values related to their five design levels (−2 to +2) in the DOE-RSM algorithm. ...
... In addition, the apparent cohesion increased by the equivalent composite layer can be determined from the results of triaxial compression tests using the equations provided by Rajagopal et al. (1999). Hence, the geocells and infill materials could be regarded as a homogeneous flexible slab, which is known as the Equivalent Composite Approach (ECA) and is widely used in numerical calculations (Hegde and Sitharam, 2013;Hegde and Sitharam, 2015a;Hegde and Sitharam, 2015b;Hegde, 2017;Ujjawal et al., 2019;Kabiri Kouchaksaraei and Bagherzadeh Khalkhali, 2020). ...
Although geocells have been extensively used to improve the performance of road embankments and slopes, their positive effect on shear strength under various shear failure scenarios has not been sufficiently emphasized. This paper attempts to fill this research gap through a series of numerical studies and presents ongoing research. First, FLAC3D is adopted to simulate two large-scale direct shear tests, and the outcomes are compared with laboratory test results reported in the literature. Then, the layout of the geocell in the shear box, the angle between the geocell layer and the shear plane, and the aspect ratio of the geocells are investigated to analyze the effects of each factor on the shear strength of the geocell-reinforced layer. The findings confirm that the geocell-reinforced layer exhibits substantial anisotropy, which is caused by variations in the shear failure plane. When the shear plane is near the center of the geocell, or the angle between the shear plane and the horizontal plane is less than 45 degrees, the geocells can provide higher shear strength. The shear strength of the geocell-reinforced layer can also be improved by increasing the aspect ratio or geocell height, where the apparent cohesiveness and friction angle are increased by 156% and 13%, respectively, over a range of aspect ratios from 0.394 to 1.575.
... In this study, the pressure-settlement behavior noted in fabricated geocells corresponds with the findings of small-scale tests conducted by various researchers [7,22,37,43,71,72,[74][75][76][77][78][79]. This alignment is particularly evident when footings, reinforced with these geocells in dense sand, display a pronounced strain-hardening response, Note: The acronyms a, b and c represent the secant stiffness of geocell material at 5% strain, failure and 2% strain, respectively. ...
The complexities of scaling have long presented challenges in applying small-scale test results of geocell-reinforced footings to field conditions in geosynthetic engineering. There has been no research that thoroughly examines the scaling of both geometry and material stiffness in geocell-reinforced footing systems although limited studies have attempted to scale geocells using alternative materials with lower strength, such as simile paper, non-woven geotextile etc. Therefore, this is a leading study to address the complexities of scaling using 3D-printing technology, where both geometry and tensile stiffness of geocell were accurately scaled using scaling laws. In the present study, the impact of scaling on the performance of strip footings reinforced with both traditional fabricated and 3D-printed geocells in terms of pressuresettlement response and improvement factors were assessed. The results indicated that 3Dprinted geocells offered significant advantages in customization and rapid prototyping of field scale. Specifically, the strip footings reinforced with fabricated geocells showed up to 65% higher improvement factors in both loose and dense soils compared to those using the scaled 3D-printed geocells. Furthermore, the footings reinforced with scaled geocells using 3Dprinting technologies closely aligned with existing large-scale test results regarding improvement factors, which were further validated through various numerical analyses. These findings offer new perspectives for optimizing and applying 3D-printed geocells in geotechnical engineering and address the longstanding challenge of scaling geocellreinforcement systems in small-scale model tests.
... In this study, the results of the model tests performed by Gedela and Karpurapu (2021b), Hegde and Sitharam (2015a), and Yang et al. (2010) were adopted to verify their applicability. Detailed information is presented in Table 5. ...
... High tensile strength, bending resistance, and shear strength are provided by the geocell-reinforced bases, and the failure planes are intercepted from the subsoil layer [130]. On the basis of a prior study [49][50][51][52], the reinforcing mechanisms provided by geocell material were reported as follows. ...
Geocell has become increasingly popular as reinforced material in various fields of civil engineering over the last few decades. Geocells can be a solution to the problems associated with paved and unpaved road construction over weak soil. Many researchers have conducted laboratory model testing, field trials, numerical, and analytical studies to assess the significant impact of geocell reinforcement. The current paper reviews various studies available in the literature and provides a summary of the main contributions. The current study illustrates that improved performance owing to geocell reinforcement is dependent on several factors and variables, including the relative density of infill material, geocell rigidity, and geometry, placement location of geocell and geocell type. Furthermore, a comprehensive review of the various literature and design guidelines was presented to assess the performance improvement of geocell-reinforced pavement in terms of rut depth, vertical stress distribution, resilient modulus, modulus improvement factor, and traffic benefit ratio. The important findings from a review of the relevant literature indicate that the geocell provides confinement, membrane effect, and larger stress distribution, resulting in a greater load-carrying capacity and modulus of reinforced soil. Several studies highlighted that due to the usage of geocells as a layer of reinforcement, a 13 to 71% reduction in rut depth occurred. Furthermore, the modulus of the geocell-soil composite may improve by 2.5 to 3.5 times of modulus value of the unreinforced section due to the increment of the geocell height.
... The numerical modelling of the soil reinforced with a single geocell subjected to a vertical load by approximating the actual honeycomb shape of the geocell as a sinusoidal curve was carried out by Yang et al. [34]. The actual honeycomb shape of the geocell was modelled by obtaining the coordinates of the expanded geocell through the digitisation of the photographs to simulate the static plate load tests on geocell reinforced sand [35][36][37]. The behaviour of machine foundations on geocellreinforced sand by modelling the actual honeycomb shape of the geocell was studied by Venkateswarlu et al. [38]. ...
Construction of retaining walls using geocell stacks as facing has many advantages such as inherent flexibility, reduction in construction cost and time, dispensability of concrete facing, and overall improvement in stability. Though soil–geocell interactions at element level are well understood, various aspects of these interactions at a bigger scale, specifically under seismic conditions are not established. In this study, retaining walls with geocell facing were tested under seismic conditions through shaking table model tests. The study is focussed on understanding the effects of geocell stiffness, slope inclination, and infill type on the acceleration and displacement response of geocell walls under seismic conditions. Results showed that battered-faced walls performed much better than vertical-faced walls. Even the low-strength geocells could offer great resistance to seismic shaking. Further, to understand the behaviour of the geocell retaining walls under actual earthquake loading, 3D modelling of the wall considering the actual shape of geocells was carried out using FLAC3D. The results showed that the retaining wall subjected to acceleration time histories having the same peak acceleration and Arias intensity underwent different lateral deformations. This indicates that the frequency content of the input motion plays a major role in the performance of the geocell retaining walls.
... Geosynthetic reinforcements, as a widely applicable soil reinforcing technique, offer excellent properties in tension, lateral confinement and interlocking with soil particles [12][13][14][15][16][17][18]. Geocells, of the most common geosynthetic reinforcements used to achieve soil improvement, provide several benefits [19][20][21][22][23][24][25][26][27][28][29][30][31][32][33]. Firstly, the shear strength of the composite soil reinforcement mattress is increased by a lateral confinement effect owing to the geocell's honeycomb structure fully arresting lateral spreading of the soil. ...
... Where S U is the settlement of the unreinforced sand bed at a given pressure, and S R is the settlement of the reinforced sand bed at the same pressure. Many researchers have computed the improvement in bearing capacity and reduction in settlement with the inclusion of reinforcements through the aforementioned dimensionless quantities (Harikumar, Sankar, and Chandrakaran 2016;Hegde and Sitharam 2015;Makkar, Chandrakaran, and Sankar 2017;Thallak, Saride, and Dash 2007;Vinod, Bhaskar, and Sreehari 2009). Figure 3 depicts the variation in bearing strength improvement factor for closely woven rattan mats with u/B at different settlement ratios. ...
... By analyzing some parameters, including the geocell size and modulus, depth of the geocell mattress, and the relative density of the sand, the author claimed that the top of the geocell mattress should be at a depth of 0.1-time footing width to obtain the maximum reinforced performance. Following this research, subsequent studies by Ujjawal et al. 11 , Hegde and Sitharam 15 , Hegde and Sitharam 16 , Hegde and Sitharam 17 , Hegde and Sitharam 18 , Venkateswarlu et al. 19 all adopted this buried depth of geocell mattress to study the behavior of reinforced soil beds based on model or site tests. Historically, researchers have primarily focused on enhancing the bearing capacity of geocell-reinforced beds 20,21 , load distribution of geocell mattresses 22 , and vibration isolation 11,12 . ...
This paper presents a comprehensive study on the numerical and parametric study of geocell-reinforced cohesive soil beds, focusing on different infill materials. The numerical calculations were validated against model test results using FLAC 3D software. Subsequently, the verified model was expanded to the geocell-reinforced cohesive soil beds. Six cases were simulated to investigate the reinforced performance, including pressure-settlement responses, bearing capacity improvement factor, settlement reduction percentage, and surface deformation. The numerical findings emphasize that the significance of superior geocell reinforcement should not overshadow the consideration of soil infill’s mechanical properties. In the case of cohesive soil as the infill material, the poor improvement in geocell-reinforced performance may be attributed to its low modulus and cohesion. Parametric studies suggest that geocells significantly impact reinforced performance when the infill material consists of foundation soil with a higher modulus and lower cohesion. Further, according to this numerical study, cohesionless soil with a modulus of 20 MPa and friction of 40° is the optimum infill soil in pockets to reinforce cohesive soil beds.
... Although these techniques are quite simple, it is impractical to model geocells as the soil layer when simulating the issue of the single-cell geocell exposed to uniaxial compression. Hegde & Sitharam (2015) utilized the circular-shaped pocket geometry for the numerical assessment of geocellreinforced pavements. They showed the need to accurately simulate the real form of the geocells and its accuracy in the simulation results. ...
Reinforced flexible pavement is being constructed to increase pavement service life and make optimal use of geosynthetics. Appropriate selection of geogrid stiffness within the asphalt concrete layer and proper choice of subgrade materials may lead to a workable solution. Rut depth estimation under the various contact pressure with the varying subgrade modulus is the best approach to identifying the suitable geogrids range. A 2D axis-symmetrical numerical model was developed to simulate the typical pavement response under heavy traffic loading. Elasto-plastic behavior of soil material was considered for the base and subgrade layer. Initially, the developed numerical model was validated with the published experimental simulations, and the obtained numerical results are in good agreement with the experimental results. Further, this study presents the estimation of rut depth for the various subgrade modulus, cyclic wheel loading, and geogrid stiffnesses from the numerical simulations. The results show the beneficial effect of the appropriate range of geogrid stiffness in the asphalt concrete layer. Qualitative discussions are made from parametric analyses on the variation of vertical surface deformations of reinforced flexible pavements under repeated wheel loading. The results indicated that the rut depth increased for pavements with a lower subgrade modulus. However, this study observes a significant reduction in pavement's rut depth with varying geogrid stiffness from 100 kN/m to 400 kN/m. Thus, selecting geogrid with a stiffness greater than 400 kN/m is advisable for the better long-term performance of the pavements having lower subgrade modulus.
... Most numerical studies use the equivalent composite approach to simulate the geocell [46,47]. In some studies, the honeycomb structure of geocells has been simplified to an Stress-strain curve of the specimen made with geocellreinforced soil equivalent square or cylindrical shape for ease of modeling [48][49][50]. Some researchers [51][52][53][54] modeled geocell with its real shape. ...
In this work, a new type of geocell with high-strength characteristics was applied to support the embankment to improve its performance. To evaluate the performance of an Embankment Reinforced by a New-style geocell, the geocell-reinforced embankment was designed to obtain optimal design parameters by using Abaqus Finite Element program. The parameters, including the aperture size of the geocell, reinforcement spacing, reinforcement length, slope rate, and slope step, were determined by analyzing the mechanical behavior of the embankment reinforced by a new-style geocell based on the safety factor, lateral displacement, and tensile stress on the geocell-reinforced embankment. Then a numerical simulation, where the performance of geocell-reinforced embankment was evaluated in terms of horizontal displacement, vertical displacement, tensile stress, shear stress, and plastic zone compared with unreinforced embankment, was conducted to evaluate the improvement effects of the new-style geocell on the embankment performance. The results revealed that the concentration area of horizontal displacement for the geocell-reinforced embankment, mainly located near the bottom of the embankment, was significantly reduced. The vertical displacement and differential settlement of the embankment were reduced by 13% and 79.6% after reinforcing, respectively. Moreover, the provision of geocell reinforcement greatly influenced the internal stress of the embankment, resulting in a 40% reduction in the distribution area of tensile stress. The comparison between the geocell-reinforced and unreinforced embankment on the plastic zone indicated that the slope toe of the embankment was the weakest position for shear failure, regardless of whether it was reinforced or not.
... The failure mechanism of on reinforced soil -based footings is known not to be a simple issue, considering the limited knowledge relating to their load settlement behavior. Many experimental, numerical, and analytical studies have investigated the behavior of reinforced soil foundations for different soil types [11][12][13][14][15][16][17]; all these studies demonstrated that the bearing capacity of shallow foundations increases when the foundation is reinforced. The first researchers to examine the impact of soil reinforcement on the increase of the bearing capacity of shallow foundations were Binquet and Lee [4,18]. ...
... According to the consequences of these studies in the literature, the load-settlement response and peak carrying capacity of the soil can be improved by placing reinforcement in the soil within a certain embedment depth according to which no significant improvement occurs. In addition, innovative methods have been presented in the literature to increase the performance of geosynthetic sheets, such as the use of a geocell-mat geosynthetic inclusion (Avesani Neto et al., 2013), the installation of a multilayer reinforcement (Hegde & Sitharam, 2015), the application of a granular soil layer over the geosynthetic (Biswas et al., 2016), and the use of wraparound geotextile methods (Ahmad & Mahboubi, 2021;Aria et al., 2019b;Kazi et al., 2016;Wang et al., 2018). ...
This study reports the results of experiments conducted on strip foundations with and without reinforced geogrids over fine sand and with a wraparound geogrid arrangement. A load up to 25 kN was applied to the strip foundations to determine the loading-settlement response. These tests examined the number of planar and folded geogrid sheets, the placement of folded geogrids in the soil bed, the thickness of folded geogrid sheets, the length of wraps and overlaps, and the spacing between folded and planar geogrid sheets. The results indicate that the performance of the foundations due to static loading is better for folded geogrid-reinforced sand than for planar geogrid-reinforced sand. Overall, the results demonstrate that reinforced soil foundations with sufficiently folded geogrid layers behave much stiffer and thus can support higher loads with a lower settlement than planar reinforced soils. Moreover, the results indicate that the values of the embedment depth of the overlap element (d), the lower part (D), and the thickness (x) of the folded geogrid are 0.2, 0.4, and 0.2 of the foundation widths (B), respectively. As a result, by increasing the number of geogrid layers, the settlement rate is reduced significantly, and it is recommended that these layers be placed vertically without vertical spacing (h/B = 0).
The loading and unloading actions of rollers during the construction of geocell-reinforced soil subgrade lead to the compaction of infill materials, which further causes the geocell pockets to expand. Due to the pre-tensioning of the geocells, such responses result in increased lateral confinement of the infill soil prior to the service of the geocell-reinforced soil subgrade. The phenomenon was defined as the Compaction-induced Prestressing Effect (CIPE) in this paper, which was verified through the finite difference method-discrete element method (FDM-DEM) coupling numerical simulations on reinforced subgrade with the aid of FLAC 3D and PFC 3D software. An equation was proposed to quantitatively describe the influence of CIPE on the initial stiffness of the reinforced subgrade. Furthermore, experiments and numerical simulations were employed to investigate the evolution of Modulus Improvement Factor (MIF) values over time, where the rheological properties of geocells were considered. The findings indicated that geocell sheets experienced a normal deformation of approximately 0.5 mm and tensile strains ranging from 0.17% to 0.21% following vibration compaction. The MIF values ranged from 2 to 6 due to CIPE. When the prestressing strain of the geocell sheet reached 0.1%, the geocell strain stabilized within 300 seconds, with the MIF decreasing by 27.6%.
This study introduces a novel semi-empirical method that conceptualizes the geocell layer as an additional surcharge and expanding the effective footing width. This method integrates reinforcement mechanisms, including confinement, stress dispersion, and the membrane effects, to calculate the ultimate bearing capacity of foundations reinforced with geocells. An extensive analysis on the angle of load dispersion was conducted, drawing upon numerous studies from the literature and considering various influencing parameters. The proposed calculation method for both drained and undrained conditions was validated using 130 small- and large-scale experimental results. The effectiveness of the proposed method is assessed across different failure modes, soil relative densities, geocell characteristics, load eccentricities, and footing shapes. The study revealed that the calculated bearing capacities generally aligned with the point where the pressure-settlement curve transitions to a steep and relatively straight tangent, which has been identified by various researchers as the ultimate load. Furthermore, existing methods for calculating the bearing capacity of geocell-reinforced soil inadequately capture the pressure-settlement responses, mainly due to differing failure modes between unreinforced and reinforced soils. In contrast, the proposed method, which does not necessitate unreinforced test results, proves effective in determining the ultimate bearing capacity of reinforced soil within acceptable settlement limits.
Geocell-reinforced slopes have proven to be one of the most efficient techniques of slope stabilization. However, the efficacy of utilizing geocell layers as fascia or reinforcement in slopes against seismic loading is yet to be intricately ventured. In this paper, numerical plane-strain modelling of geocell-reinforced slopes is carried out to study their response against seismic loading. Both pseudostatic analysis and non-linear time-history analysis are carried out considering a chosen strong motion history. Equivalent Composite Approach (ECA) is employed in modelling the 3-dimensional geocell layer as an equivalent 2-dimensional soil-geocell composite by introducing improved strength and stiffness imparted by the geocells. The improved strength is obtained from the additional confining pressure induced by the geocell pocket boundaries. The improved stiffness of the soil-geocell composite is calculated from the stiffness of the unreinforced slope material and the tensile modulus of the geocell material. Three different configurations of the placement of geocell layers are implemented to evaluate the response, where the geocell layers are introduced in the form of fascia, reinforcement, or a combination of both. The global stability of the reinforced slope sections is analysed using pseudostatic seismic coefficients assessed through different techniques, while the acceleration response and deformation of the slope face are analysed using an acceleration-time history input. The influence of geocell layers on the hysteresis behaviour of the slope face and on the development of potential slip surfaces is also investigated to yield motion specific observations.
Geosynthetic reinforcements have become increasingly popular in the last few years for usage in a variety of infrastructure projects because of their advantageous properties. One kind of geosynthetic that is produced as three-dimensional interconnected cells is called geocell. It can be used as a reinforcement to enhance base course behavior by offering lateral confinement, which increases the base course's stiffness and strength while lowering surface permanent deformation. Therefore, this research aims to study the behavior of strip footing rested on a geocell reinforced sand bed experimentally and numerically. In this research, a single geocell, filled with sand, was exposed to a vertical load until reaching failure. The testing process was modeled through the use of PLAXIS 3D numerical software. The effects of using a geocell as a reinforcement on load-bearing capacity and settlement at variable parameters, such as depth of placement, height, and length of reinforcement under axial compression load were studied. The results indicate that using geocell as soil reinforcement leads to a noticeable improvement in the bearing capacity and settlement response of the soil. The recommended geocell layer height, length, and placement depth that give the maximum bearing capacity improvement are presented and discussed. The effect of using geocell as soil reinforcement on the ultimate bearing capacity is estimated by bearing capacity ratio (BCR) and modulus of subgrade reaction (ks).
The material point method (MPM) has garnered significant attention in recent years owing to its advantages in solving soil–water-structure interaction problems involving large deformations in geotechnical engineering. The MPM combines the benefits of point-based and mesh-based approaches (finite element method) with both Eulerian computational mesh and continuum descriptions of materials. The successful integration of MPM in simulated landslides, internal erosion, and excavation has been frequently reported. However, solving the soil–geosynthetic interaction problem with the MPM has not been explored, although such problems often entail large deformations. The goal of this study is to collate studies on the simulation of geosynthetics and their interactions with soil using MPM. This paper first discusses the basics of MPM and the formation of thin membrane materials using MPM. It also includes limited applications of MPM in simulating soil–geosynthetic interactions. The applications demonstrate that the MPM is particularly effective in resolving large deformation problems associated with geosynthetics, including problems of landfill settlement, reinforced-slope stability, and geocontainer dropping.
Most research studies on the behavior of footings on geocell-reinforced slopes were conducted using experimental model tests on small-scale slopes. Very few studies can be found in relation to 3D analyses using detailed geocell structures. It is, therefore, the aim of the present study to investigate this problem by using a 3D finite element analysis. The study begins with verifying the accuracy of the applied finite element method using the results of the experimental model tests on the unreinforced and geocell-reinforced footings on slopes. It continues with studying the effects of main design factors such as the slope angle (β), the depth of the geocell mattress (u), the soil internal friction angle (ϕ), and the footing setback (a) on the bearing capacity of the geocell-reinforced footings. Numerical results suggest that an increase in soil internal friction angle and a decrease in slope angle would both enhance the bearing capacity of unreinforced and reinforced footings. The geocell reinforcement proves to be more effective in improving the bearing capacity of steeper slopes with small friction angles. In addition, the optimum depth of the geocell placement was found to be 0.1 times the footing width (0.1B) regardless of the β and ϕ. Irrespective of the β, the optimum footing setback ratio (a/B) was obtained at 0.5. As a/B ˃ 2, the effect on bearing capacity vanishes. At a constant footing setback ratio (a/B < 2), the use of geocell reinforcement is more effective for steeper slopes. The findings in this numerical study are of practical significance to the geotechnical engineering community.
To evaluate the benefit of geocells of different geometrical configurations for pavement application, full-scale instrumented model tests were performed on pavement sections reinforced with geocells of different geometrical configurations subjected to monotonic and repeated loading. The responses studied were stress distribution in different pavement layers, induced strains in geocell walls, and settlement characteristics. The reinforced
sections exhibited a significant reduction in rut depth as well as localized stress concentration compared to the unreinforced section. The reduction in rut depth was found to be influenced by the geocell height as well as weld spacing. The geocell reinforcement was found to distribute the stresses in the subgrade and subbase layers more efficiently, thus reducing the stress concentration in these layers. The strain measurements were found to be higher at the bottom of the geocell walls indicating a higher confinement effect on a lower part of the geocell. In the field, mostly geocells of 356 mm weld spacing and 150 mm height (SW356-H150) are used. However, this study suggests that a geocell of 330 mm weld spacing and 100 mm height (SW330-H100) having approximately 30% lower cost compared to SW356-H150 is as effective in reducing the rut depth and localized vertical stress distribution.
The use of geogrid reinforcement has proven to be an effective measure to improve the anchor uplift capacity. However, previous studies are limited to analyzing the axial pullout capacity of plate anchors. In comparison, the anchor foundations employed in field are compelled to resist both uplift and lateral forces. In most cases, the foundation's safety against lateral forces dictates the design criteria for tall structures. Therefore, improving the foundation's lateral load-bearing capacity is of utmost importance. This paper presents a three-dimensional numerical analysis of anchor foundations in geogrid-reinforced sand under uplift and lateral forces. The results highlight the benefits of geogrid reinforcement on the anchor's uplift and lateral load response. The geogrid reinforcement is modelled using cable elements capturing the actual apertures responsible for tensile force mobilization along the geogrid ribs. A significant reduction in the displacements of the anchor foundation is observed in geogrid-reinforced sand, both in horizontal and vertical directions, when combined loads are applied on the anchor. However, the maximum reduction is found in the case of vertical uplift forces for higher values of the applied load. The practical implication of this study is demonstrated using a performance-based design example of transmission tower foundations in geogrid-reinforced sand.
A detailed numerical analysis has been accomplished to explore the influence of geometrical parameters of geocell reinforcement on the load carrying behavior of footing using three-dimensional finite element techniques. The influencing parameters considered such as shape, height, pocket size, stiffness of geocell reinforcement, and friction angle of infill materials. Results indicate that the inclusion of the geocell reinforcement irrespective of the shape of geocells significantly enhances the strength and stiffness of the foundation system. However, the pressure-settlement behavior is noticeably influenced by the shape of the geocells. The load carrying capacity is found to be minimum for square shaped (i.e., 400 kPa) followed by circular, diamond, and honeycomb shapes (i.e., 1000 kPa) of geocells. With increase in height of geocell mattress, the performance of the foundation system increases noticeably. The findings indicate that the load bearing capacity increases significantly up to a height ratio (H/B) of 1.5, beyond which further increment found to be marginal. Additionally, the efficacy of the system improves with increase in stiffness of reinforcement and reduces with increase in geocell pocket size. Furthermore, it is evident that the higher frictional angle of the soil mobilizes enhanced resistance on the interface, improving the overall performance.
One of the most governing factors in the design of the foundation supporting the vibration sources is to reduce the amplitude of vibration. Vibration generated from industrial machinery is frequency dependant, and frequency has a significant influence on these design factors. Therefore, this manuscript describes the influence of frequency of loading on the vibration mitigation efficacy and the behaviour of geocell reinforced bed using the experimental and numerical studies. As part of the experimental study, a series of field vibration tests have been performed over the unreinforced and geocell-reinforced soil beds by varying the frequency of loading between 15 and 45 Hz. Using field tests, different vibration isolation parameters namely, velocity reduction ratio (VRR), vibration mitigation efficiency and attenuation coefficient have been studied. Numerical analysis has been conducted using FLAC3D to demonstrate the variation of VRR with respect to some of the key parameters namely, footing shape, geocell area, and relative density of infill. From the experimental results, vibration mitigation efficiency of geocell reinforced beds corresponding to distinct frequencies of loading i.e., 15 Hz, 25 Hz, and 45 Hz was observed as 39%, 43%, and 49%, respectively. The attenuation coefficient of a geocell reinforced bed was found to increase with the increase in frequency. Use of geocell reinforcement, notably minimized the strain generated over the foundation bed. However, the strain corresponding to the unreinforced and geocell-reinforced beds was increased with the increase in frequency of loading. VRR was found to decrease with the increase in geocell area and relative density of the infill material.
The dynamic stresses in many subgrades for old railways exceed the bearing capacity of the fillers. The geocell has been used to reinforce weak subgrades and achieve a quick attenuation in the dynamic stress. In this study, a series of field tests were conducted to investigate the dynamic stress attenuation characteristics in a weak subgrade reinforced with a geocell. A coupled finite element-discrete element model was developed to analyze the mechanism of the stress attenuation from a multiscale perspective. The results indicated that increasing the geocell height or decreasing the weld distance resulted in an increase in the attenuation rate. There was a threshold for the weld distance, below which its impact on the stress attenuation rate became negligible. When the weld distance was small, the dynamic stress attenuation was attributed to the geocell induced lateral confinement for the infilled soil. With the weld distance increasing, the deformation of the geocell increased and the membrane effect was further mobilized, which contributed to the dynamic stress attenuation. Based on the field test and numerical results, a design method was proposed to determine the reinforcement parameters of geocell-reinforced subgrade, aimed at improving dynamic stress attenuation and preventing subgrade distress.
A novel three-dimensional numerical model for the biaxial geogrid reinforcement is proposed in this paper that
can incorporate the direction-dependent strength and stiffness properties and the actual grid-like structure of the
geogrid reinforcement, which are crucial for soil-geogrid interactions. First, the numerical model consisting of
cable structural elements is validated against wide width tensile test results reported in the literature. Next, the
geogrid reinforcement model is validated with published experimental and numerical results on reinforced
foundations. Two different cases, the bearing capacity of foundation in geogrid-reinforced soil and the uplift
capacity of anchor plates in geogrid-reinforced sand, are selected from the literature for validation. The numerical results reasonably agree with the experimental results for both the bearing and uplift cases. The results
indicate that the proposed approach can predict the behavior of geogrid reinforcement and can be used for
modeling and analysis of other geogrid-reinforced structures.
This paper presents the results of experimental and numerical investigations on the behaviour of strip footing resting on geogrids-reinforced dune sand. The tests were performed on a rigid steel tank having glass sides and the model footing is made of steel. Footing depth, geogrids depth, and number of geogrid layers were studied. Footings were placed at the surface of the sand or at a depth of 0.25B below the surface of the sand. Geogrids were placed at different depths below the footing from 0.25B to B. The number of geogrids layers was varied from 0 to 4 layers. The results indicated that using more geogrids layers improved the ultimate bearing capacity of the strip footings and reduced the settlement. The bearing capacity improvement factor increased from 1.2 for the case of one geogrid layer to more than 3 for the case of 4 geogrid layers. For the case of one layer of geogrids the highest improvement is when the depth of the reinforcement below the footing was between 0.5 B and 0.75B. For the case of two layers of geogrids, the highest improvement is when the reinforcements are placed at depths of 0.25B and 0.75B below the footing. Results obtained from finite element analysis using the program MIDAS are generally in good agreement with those obtained from the laboratory model tests. Further, numerical analysis indicates that the geogrids redistribute the applied load on larger area of the soil, thus, reducing the settlement.
Large-scale experiments with cyclic loading were conducted to determine how incorporation of high-density polyethylene (HDPE) geocells affects the rutting properties of working platforms and resilient properties of a subbase in a pavement structure over soft subgrades. Four different geocells were used in this study to reinforce common subbase/base course gravel. Experiments were performed with 225 mm and 450 mm thick unreinforced and reinforced gravel and a crushed rock that is typically used for conventional cut-and-fill working platforms. Experiments were conducted to simulate loading conditions both during construction due to construction equipment and after construction due to traffic conditions over the asphalt pavement once the pavement structure is constructed. Materials used in this study were compacted to 90% relative compaction based on standard Proctor to determine the effect of geocells specifically with gravel material that is compacted to lower than typical standards. Deflections, modulus of subgrade reaction and resilient modulus of each section were evaluated. In summary, presence of geocells reduced the plastic deflection of the working platforms by 30-50%, improved the resilient modulus of the subbase by 40-50%, and the modulus of subgrade reaction by more than 2 times.
Large-scale cubical triaxial tests were conducted to investigate the behavior of reinforced and unreinforced subballast under cyclic load. Granular material with an average particle size (D50) of 3.3 mm and geocell with a depth of 150 mm and nominal area of 46×103 mm2 were used in this study. The laboratory results proved that subballast stabilization was influenced by the number of cycles (N), the confining pressure (σ'3), and the frequency of train-caused vibration (f). The experimental results also confirmed that the geocells influenced the subballast behavior under cyclic loading, particularly at low confining pressure and high frequency. The additional confining pressure induced by the geocell reduced its vertical and volumetric strains. The optimum confining pressure required to reduce excessive volumetric dilation also was identified in this study. An empirical model using a mechanistic approach is proposed to determine the additional confinement induced by the geocells, as well as the practical implications of the experimental outcomes.
This paper describes the reinforcing effects of multiple layers of geocell in combination with rubber-soil mixture layers in sand, and compares their behaviour with that of the multilayered geocell reinforcement alone, using plate loading at a diameter of 300 mm. The plate load tests were performed in an outdoor test pit, dug in natural ground measuring 2000 × 2000 mm in plan and 700 mm in depth. The geocell used in the tests was non-perforated with pocket size 110×110 mm2 and height 100 mm, fabricated from continuous polypropylene filaments as a nonwoven geotextile. The optimum embedded depth of the first layer of geocell and the vertical spacing of geocell layers were found to be approximately 0.2 times the footing diameter, and the optimum percentage of rubber replacement was found to be around 8% by weight of the soil mixture. Both bearing capacity increase and settlement reduction were highest when multiple layers of geocell and rubber reinforcement were used. Results show that the reinforcements' efficiency decreased as the number of reinforcement layers increased, particularly at low settlement ratios. Higher bearing capacity and lower settlement were achieved by replacing the layers beneath the geocell layers with the rubber-soil mixture. At a ratio of settlement to plate diameter of 2%, the values of bearing pressure were in the ratio 1:2.3:3 for, respectively, the unreinforced installation, the installation with three layers of geocell, and the installation with three layers of geocell and rubber-soil between the layers. The inclusion of the geocell layers reduces the vertical stress transferred down through the foundation bed by distributing the load over a wider area. For example, at the pressure of 550 kPa applied on the soil surface, the transferred pressure at the depth of 510 mm is about 48%, 34% and 27% for the reinforced bed with one, two and three layers of geocell, respectively, compared with the stress in the unreinforced bed. Furthermore, use of the combination of geocell and rubber-soil mixture layers is more effective than use of geocell layers only in reducing the stress transferred downwards. For example, 350 mm beneath a soil surface that carries a stress of 830 kPa, the vertical stress is 15% less when two geocell layers are combined with two rubber-soil mixture layers than when there are only two geocell layers.
The paper describes the results of a series of large-scale triaxial tests carried out on 200-mm-high isolated geocell-soil composite specimens and unreinforced soil specimens. Two different aggregate soils were used in the test program. The reinforced specimens were tested with a height-to-diameter ratio of unity, which matches the dimensions of these systems in a typical base reinforcement application. The results illustrate the stiffening effect and strength in-crease imparted to the soil by the enhanced confinement effect. Comparison of reinforced and unreinforced soil specimens shows that the frictional resistance described by the peak friction angle of the soil infill is applicable to the composite structure as well. A simple elastic membrane model can be used to estimate the additional apparent cohesion present in the composite structure.
Geocells are three-dimensional expandable panels with a wide range of applications in geotechnical engineering. A geocell is made up of many internally connected single cells. The current study discusses the joint strength and the wall deformation characteristics of a single cell when it is subjected to uniaxial compression. The study helps to understand the causes for the failure of the single cell in a cellular confinement system. Experimental studies were conducted on single cells with cell pockets filled up with three different infill materials, namely silty clay, sand, and the aggregates. The results of the experimental study revealed that the deformation of the geocell wall decreases with the increase in the friction angle of the infill material. Experimental results were also validated using numerical simulations carried out using Lagrangian analysis software. The experiment and the numerical results were found to be in good agreement with each other. A simple analytical model based on the theory of thin cylinders is also proposed to calculate the accumulated strain of the geocell wall. This model operates under a simple elastic solution framework. The proposed model slightly overestimates the strains as compared with experimental and numerical values.
This paper presents the results of laboratory model tests and numerical studies conducted on a square footing resting on geocell reinforced sand and clay beds. Using suitable scaling considerations, a model footing size was arrived from the prototype raft foundation. Commercially available geocells made up of polyethylene having an equivalent pocket diameter of 0·25 m and aspect ratio of 0·6 were used in the experimental investigation. Clean sand was used to fill the geocell pockets in both sand and clay bed tests. Test results of unreinforced, geocell reinforced, and geocell reinforced with additional planar geogrid at the base of the geocell cases are compared separately for sand and clay beds. Results reveal that the use of geocell increases the ultimate bearing capacity of the sand bed by 2·4 times and clay bed by 3·2 times. Provision of the planar geogrid at the base of the cellular mattress arrests the surface heaving and prevents the rotational failure of the footing. Moduli of subgrade reaction values indicate that the contribution of the geocell reinforcement exists even at very low settlements. Using the concept of equivalent composite model, the three-dimensional nature of the geocell is numerically simulated in the fast Lagrangian analysis of continua in 2D (FLAC2D). Experimental and numerical results are in good agreement with each other.
A series of experiments have been carried out to develop an understanding of the performance improvement of soft clay foundation beds using stone column-geocell sand mattress as reinforcement. It is found that with the provision of stone columns, of adequate length and spacing, about three fold increases in bearing capacity can be achieved. While with geocell-sand mattress it is about seven times that of the unreinforced clay. But if combined together, the stone column-geocell mattress composite reinforcement, can improve the bearing capacity of soft clay bed as high as by ten fold. The optimum length and spacing of stone columns giving maximum performance improvement are, respectively, 5 times and 2.5 times of their diameter. The critical height of geocell mattress can be taken equal to the diameter of the footing, beyond which, further increase in bearing capacity of the composite foundation bed is marginal.
Geocell reinforced soil may be used in many areas of geotechnical engineering, however, there is little information on analysis of the behavior of geocell reinforced slopes. Due to the height of the geocell, the geocell-reinforced mattress more likely provides a beam or plate effect than a planar membrane effect. The purpose of this paper is to use beam model to simulate the geocell behavior as a flexible slab foundation which can carry both bending and membrane stresses for stability analysis of geocell reinforced slopes. In addition, the interface resistance between the geocell–soil was considered. The Young's modulus of geocell encased soil was obtained from the elastic modulus of the unreinforced soil and the tensile modulus of the geocell reinforcement using an empirical equation. Parametric studies of geocell reinforced slope are carried out by varying placement depth of the geocell layer, number of geocell layers, vertical spacing between reinforcement layers, length, thickness and Young's modulus of the geocell reinforcement. The influence of slope geometry, shear strength properties and soil compaction on the behavior of geocell reinforced slope is also discussed. The obtained results show that geocell reinforcement acts as a wide slab and thus it can restrain the failure surface from developing and redistribute the loads over a wider area. Therefore, under the geocell placement, the lateral deformation and shear strain values of the slope considerably decrease. Furthermore, the effective placement of geocell reinforcements is found to be between the middle of the slope and the middle of critical failure surface of the unreinforced slope.
Geocells have a three-dimensional cellular structure, which can be used to stabilize foundations by increasing bearing capacity and reducing settlements. However, a considerable gap exists between the applications and the theories for the mechanisms of geocell-reinforced foundations. An experimental and numerical study on the behavior of geocell-reinforced sand under a vertical load is presented. A single geocell was filled with sand and subjected to a vertical load to failure. This test process was modeled by using the FLAC3D numerical software to investigate the mechanisms of geocell and sand interactions. Experimental and numerical results both demonstrated that the geocell increased the ultimate bearing capacity and the modulus of the sand. The numerical results include the distributions of displacements in the sand and geocell walls and the distributions of tensile stresses and shear stresses acting on the geocell walls. The numerical results for geocell-reinforced sand are compared to those for sand without geocell.
This paper summarizes the development of a three-dimensional numerical model for analyzing single geocell-reinforced soil.
In this model, the infill soil was modeled using the Duncan-Chang model, which can simulate non-linearity and stress-dependency
of soil. Geocell was modeled using linearly elastic plate elements, which can carry both bending and membrane stresses. A
linear interface stress-strain relationship with a Mohr-Coulomb yield criterion was adopted to model the interface friction
between the geocell wall and the soil. By modeling the geocell and the soil separately, the interaction between the soil and
the geocell can be accurately simulated. To verify this model, a plate load test was conducted in the laboratory, in which
a 12-cm-thick sand layer reinforced by a single geocell was subjected to a vertical load from a circular steel plate. The
load-displacement curves and the horizontal tensile strain of the geocell were recorded during the test. A numerical model
was created according to the setup of the load test. The numerical results compared reasonably well with the test data.
Keywordsgeosynthetic reinforcement-geocell-numerical model-FLAC3D
The paper presents a modern outlook of the problem of bearing capacity of shallow foundations, incorporating all major contributions to the subject, along with best available solutions and appropriate numerical values of bearing capacity factors and coefficients. It is shown that the greatest shortcoming of available theories lies in their unreserved assumption of incompressibility of the foundation soil. An attempt is made to formulate for the first time rational compressibility criteria for soils subjected to foundation loads. A set of tentative compressibility factors, to be used with the classical bearing capacity equation, are given. The paper includes an analysis of the effects on bearing capacity of roughness and vertical profile of foundation base, ground-water table, presence of adjacent footings and rate of loading.
Ultimate loads of shallow foundations were analyzed. Rational compressibility criteria for soils subjected to foundation loads was formulated. It was shown that the greatest shortcoming of available theories lied in the unreserved assumption of soil incompressibility. The conventional, static analysis of bearing capacity can be used for footings subjected to moderately rapid loadings.
A simple, practical procedure for representing the nonlinear, stress-dependent, inelastic stress-strain behavior of soils was developed. The relationship described was developed in such a way that the value of the required parameters may be derived from the results of standard laboratory triaxial tests. Comparisons of calculated and measured strains in specimens of dense and loose silica sand showed that the relationship was capable of accurately representing the behavior of sand under triaxial loading conditions.
The present study deals with model plate load tests conducted on geocell reinforced soft clay beds to evaluate the effect of infill materials on the performance of the geocell. Commercially available Neoweb geocells are used in the study. Three different infill materials namely aggregate, sand and local red soil were used in the study. The load carrying capacity of the geocell reinforced bed (as compared to an unreinforced bed) was found to be increased by 13 times for the aggregate infill, 11 times for the sand infill and 10 times for the red soil infill. Similarly the reduction in the settlement was in the order of 78%, 73% and 70% aggregate, sand and the red soil infill materials respectively. Results suggest that the performance of the geocell was not heavily influenced by the infill materials. Further, numerical simulations were carried out using FLAC2D to validate the experimental findings. The results from numerical studies are in reasonably good agreement with the experimental findings. The outcome of this work is successfully implemented in the construction of the geocell foundation to support a 3 m high embankment in the settled red mud in Lanjighar (Orissa) in India.
In past years, railroad transportation has been of growing interest because of its efficiency and advancement in railway technologies. However, many issues arise because of the variability in subsurface conditions along the sizeable lengths of track that exist. One very important issue is the need for significant upkeep and maintenance for railways passing over areas of poor soil conditions as a result of continuous deformation and a lack of stiffness from the foundation. One general solution for lack of substructure integrity has been confinement, applied through a variety of reinforcement types, including geocell. To investigate the effectiveness of geocell confinement on substructure integrity, a series of embankment model tests with different configurations of geocell placement (one layer and two layers of geocell) were constructed and loaded monotonically and cyclically for comparison with unreinforced, control tests. On the completion of these tests, the model embankments were simulated numerically using finite-element procedures. The results, which matched reasonably well, were then used as validation for a parametric study, observing the effects of less competent geocell material, gravel, and foundation conditions and their implications. The tests and numerical simulations demonstrate that geocell confinement effectively increased stiffness and strength of a gravel embankment while reducing vertical settlement and lateral spreading. Additionally, the parametric study shows that the use of geocell provides a composite mattressing effect that distributes subgrade stress more uniformly than without reinforcement, increasing bearing capacity and reducing settlement, especially on soft foundations. The results suggested that in some site conditions, use of geocell might be an economical alternative to frequent maintenance and/or lower train speeds.
Physical model tests were performed on geocell-reinforced foundation systems with circular footings to study the influence of the strength of the subgrade layer. Model tests were conducted with a 150 mm diameter circular footing supported on foundation beds with varied configurations. Three different series of tests were conducted using a clay subgrade with undrained cohesion in the range of 7-60 kPa and dense sand at 80% of relative density. The results showed that the performance of the geocell-reinforced foundation systems was highly dependent on the subgrade strength. A maximum improvement factor of about 11.6 was observed for very soft subgrade with c(u) = 7 kPa, which decreased to about 3 for stiffer subgrade having c(u) = 30 kPa under similar test conditions and configuration. In addition, the variation of bearing capacity improvement factors was observed to be significantly influenced by footing settlement and geocell height.
Sandy soil/aggregate, such as might be required in a pavement foundation over a soft area, was treated by the addition of one or more geocell layers and granulated rubber. It was then subjected to cyclic loading by a 300 mm diameter plate simulative of vehicle passes. After an initial study (that established both the optimum depth of the uppermost geocell layer and of the geocell inter-layer spacing should be 0.2 times plate diameter), repeated loading was applied to installations in which the number of geocell layers and the presence or absence of shredded rubber layers in the backfill was changed. The results of the testing reveal the ability of the composite geocell-rubber-soil systems to ‘shakedown’ to a fully resilient behavior after a period of plastic deformation except when there is little or no reinforcement and the applied repeated stresses are large. When shakedown response is observed, then both the accumulated plastic deformation prior to a steady-state response being obtained and the resilient deformations thereafter are reduced. Efficiency of reinforcement is shown to decrease with number of reinforcement layers for all applied stress levels and number of cycles of applied loading. The use of granulated rubber layers are shown to reduce the plastic deformations and to increase the resilient displacements compared to the comparable non-rubber construction. By optimal use of geocells and granulated rubber, deformations can be reduced by 60–70% compared with the unreinforced case while stresses in the foundation soil are spread much more effectively. On the basis of the study, the concept of combining several geocell layers with shredded rubber reinforcement is recommended for larger scale trials and for economic study.
This paper presents the case history of the construction of a 3 m high embankment on the geocell foundation over the soft settled red mud. Red mud is a waste product from the Bayer process of Aluminum industry. Geotechnical problems of the site, the design of the geocell foundation based on experimental investigation and the construction sequences of the geocell foundations in the field are discussed in the paper. Based on the experimental studies, an analytical model was also developed to estimate the load carrying capacity of the soft clay bed reinforced with geocell and combination of geocell and geogrid. The results of the experimental and analytical studies revealed that the use of combination of geocell and the geogrid is always beneficial than using the geocell alone. Hence, the combination of geocell and geogrid was recommended to stabilize the embankment base. The reported embankment is located in Lanjigharh (Orissa) in India. Construction of the embankment on the geocell foundation has already been completed. The constructed embankmenthas already sustained two monsoon rains without any cracks and seepage.
Recycled Asphalt Pavement (RAP) is the most reused and recycled material in the United States. It has been included at percentage of 15–50% in new hot mix asphalt (HMA) concrete and used as a base course material up to 100% for pavement construction. Due to the existence of asphalt in RAP, RAP base courses may have increased or excessive permanent deformation under traffic loading. To minimize such deformation, use of geocell was proposed by authors to confine RAP. To verify the performance of geocell-reinforced RAP bases and the benefit of geocell reinforcement, an experimental study was conducted on geocell-reinforced RAP bases over a weak subgrade under cyclic plate loading. A large geotechnical test box was used for the cyclic plate loading tests. The subgrade was a mixture of sand and kaolin and compacted at the moisture content corresponding to a California Bearing Ratio (CBR) value of 2%. The fractionated RAP was compacted at the moisture content close to the optimum value. A total of four sections with three base thicknesses (0.15, 0.23, and 0.30 m) were prepared and tested, which included one 0.30 m thick unreinforced section and three geocell-reinforced sections. During the testing, surface deformations and vertical stresses at the interface of base and subgrade and strains in geocell walls were monitored. Test results show that the geocell-reinforced RAP bases had much smaller permanent deformations than the unreinforced RAP bases. The geocell-reinforced bases reduced the vertical stresses at the interface between base and subgrade as compared with the unreinforced base. The strain measurements demonstrated that the thicker geocell-reinforced RAP base behaved as a slab while the thinner base behaved as a tensioned membrane. The experimental results indicated that novel polymeric alloy (NPA) geocell reinforcement improved the life of 0.15, 0.23, and 0.30 m thick reinforced RAP base sections by factors of 6.4, 3.6, and 19.4 at a permanent deformation of 75 mm as compared with the 0.30 m thick unreinforced section at the same permanent deformation, respectively. Geocell reinforcement increased the minimum stress distribution angle by 2°, 3.5°, and 7° for the 0.15, 0.23, and 0.30 m thick reinforced RAP base sections as compared with the unreinforced section.
Service trench provision and maintenance of buried pipes represent major cost items in the utilities industry. Using recycled material in order to optimize the design of the buried pipe system can lead to significant cost reductions, but only if performance is not degraded. The main purpose of the paper is to investigate the mitigation of strain in buried flexible service pipes and of the settlement of backfill over such pipes by the use of geocell reinforcement (as 3D-inclusion reinforcement) with rubber–soil mixtures under repeated loading conditions. Two rubber sizes (namely chipped and shredded rubbers), three different percentages of rubber content in the mixture, two positions for soil–rubber mixture inside the trench, four levels of repeated loading and the addition of geocell reinforcement over the pipe are the variables considered. Soil surface settlement, vertical diametral strain of the pipe (as an indication of pipe wall deflection) and stress distribution in the trench, especially on pipe’s crown, are assessed and evaluated. Both cumulative and resilient strains are considered. Using a material with high resilience, like the rubber–soil mixture, could lead to some critical issues that should be considered. These include the larger settlement of the soil surface, transfer of a larger pressure onto the pipe and, consequentially, greater pipe wall strain. For the chipped rubber and soil mixture, the pipe has the highest strains under the cyclic loading irrespective of the amount of rubber in the soil. However, the shredded rubber and soil mixture, dependent on the amount of rubber content, is able to reduce the soil settlement and plastic pipe’s diametral strain, attenuating the pipe’s accumulating strains and, finally, protecting the buried pipe from fatigue under repeated loadings. This benefit is enhanced by the combined action of geocell reinforcement over rubber-modified soil. According to the results, the minimum soil surface settlement and vertical diametral strain are provided by 5% of shredded rubber–soil mixture placed over the pipe with a geocell, giving values of, respectively, 0.30 and 0.53 times those obtained in the unreinforced and untreated soil.
Accelerated pavement testing (APT) is an effective method in evaluating pavement performances by applying controlled wheel loading under environmental conditions. This note presents the findings from an accelerated pavement test on unpaved road sections involving geocell reinforcement of sand bases. A total of four unpaved road sections were constructed. Sections 1 and 4 were unreinforced sections first with sand bases and then replaced with aggregate bases after failure. Sections 2 and 3 were sand sections reinforced with novel polymeric alloy (NPA) geocell under an aggregate cover layer. Rut depths developed in each section were measured after a certain number of wheel passes. Horizontal strains at different locations in the NPA geocell were monitored by strain gages. Test results demonstrated that the NPA geocell had a significant effect in improving the stability of unpaved roads and reducing the permanent deformation. Under the particular test condition, the NPA geocell-reinforced sand layer behaved equivalently to the A-1-a aggregate of the same thickness. The deformations of the geocell-reinforced road sections were analyzed. The test also revealed the importance of keeping the geocell structure intact to ensure the adequate performance of NPA geocell-reinforced bases. Strain gage measurements showed that the NPA geocell beneath the wheel path experienced tensile stresses whereas the geocell outside the wheel path experienced compressive stresses.
Cellular structures are widely used in civil engineering. Their design is based on the understanding of the mechanical behavior of geocells. This paper investigates the response of a single geocell to a uniaxial compression test. The geocells were cubic, either 500mm or 300mm on a side. The fill materials were sand and scrapped tire and sand mixtures in different mass ratios. The envelope of the geocell was made up of a hexagonal wire netting cage and a containment geotextile. The response of the geocell is discussed based on the axial load and displacement measurements as well as the change in geocell volume.The axial load was found to be globally governed by the interaction between the fill material and the envelope, which depends on the shape of the wire mesh and the volumetric behavior of the fill material.
A numerical simulation of laboratory model tests was carried out to develop an understanding of the behaviour of geocell-reinforced sand, and soft clay foundation beds under a circular footing. The influence of the geometrical parameters of the geocell (width, b and height, h) on the overall performance of the footing was investigated and the pressure-settlement responses of geocell-reinforced foundation beds were predicted and compared with the unreinforced test results. Simulations were also carried out on conventional-type planar geogrid reinforcement to study the relative performance of both reinforcement forms. The influence of the boundary constrains on the behaviour of the foundations was also studied. In all the cases, good agreement between the results obtained from numerical simulations and laboratory experiments was observed. The results demonstrated that the geocell mattress redistributed the footing pressure over a wider area thereby improving the performance of the footing. The pressure-settlement responses corresponding to geocell-reinforced beds were found to be much stiffer in comparison with the unreinforced case indicating that a substantial reduction in footing settlement can be ascertained. The influence of rigid boundaries on the results of reinforced foundation beds in this study was found to be negligible.
This paper studies the influence of geocell confinement on the strength and stiffness behaviour of granular soils. A large number of triaxial compression tests were performed on granular soil encased in single and multiple geocells. The geocells were fabricated by hand using different woven and nonwoven geotextiles and soft mesh to investigate the effect of the stiffness of the geocell on the overall performance of geocell–soil composite. In general, it was observed that the granular soil develops a large amount of apparent cohesive strength due to the confinement by the geocell. The magnitude of this cohesive strength was observed to be dependent on the properties of the geosynthetic used to fabricate the geocell. The stiffness of the composite was also found to increase with the provision of geocell reinforcement. The results have shown that using three interconnected cells in the testing programme is adequate to simulate the performance of geocell reinforcement layer consisting of many interconnected cells. A simple methodology has been presented in the paper to estimate the magnitude of the apparent cohesive strength developed by the granular soil as a function of the geometric and material properties of the geocell.
Synopsis
In the undrained triaxial compression test the rubber membranes enclosing the specimens give rise to an apparent increase in strength. This article presents the results of tests to determine the magnitide of this effect together with an approximate theoretical treatment.
Triaxial tests on remoulded London clay, employing rubber membranes of three different thicknesses, when compared with unconfined compression tests at the same moisture content show that the strength contributed by the rubber membrane is:— independent of specimen strength proportional to the stiffness of the membrane independent of cell pressure.
In compression tests, with the specimen enclosed in a rubber membrane but with no lateral pressure, the effect is smaller than in the normal triaxial test.
Filter paper drains, used to accelerate consolidation, add further to the compression strength and consequently a larger correction must be applied to the measured strength.
A method for estimating the rubber correction from a simple extension test on a typical membrane is suggested.
Dans l'essai de compression non-drainée triaxial, les membranes de caoutchouc renfermant les spécimens produisent une augmentation apparente de résistance. Cet article donne les résultats des essais faits pour déterminer la grandeur de cet effet, ainsi que le traitement théorique approximatif.
Des essais triaxiaux sur de l'argile de Londres remoulée, employant des membranes de caoutchouc de trois épaisseurs différentes, ont été comparés à des essais de compression libre à la même teneur en humidité, et montrent que la résistance contribuée par la membrane de caoutchouc est:— indépendante de la résistance du spécimen, proportionnelle à la raideur de la membrane, indépendante de la pression de la cellule.
Dans les essais de compression avec le spécimen renfermé dans une membrane de caoutchouc mais sans pression latérale, l'effet est moindre que dans l'essai normal triaxial.
L'épuisement par papier-filtre, employé pour accélérer la consolidation, ajoute encore à la résistance à la compression et, par conséquent, une correction plus importante de la résistance mesurée doit être faite.
Une méthode est proposée pour évaluer la correction par rapport au caoutchouc en partant d'un essai d'extension simple sur une membrane-type.
Geocell, one type of geosynthetics manufactured in the form of three-dimensional interconnected cells, can be used as a reinforcement to improve the behavior of base courses by providing lateral confinement to increase their stiffness and strength and reduce surface permanent-deformation. However, the use of geocells for base reinforcement is hindered by the existing gap between applications and theories. This study experimentally investigated the factors influencing the behavior (stiffness and bearing capacity) of single geocell-reinforced bases including shape, type, embedment, height of geocells, and quality of infill materials. Three of the four types of geocells investigated in this study were made of novel polymeric alloys using a new manufacturing technology. Repeatability and potential scale effects on test results were examined. The test results showed that the geocell placed in a circular shape had a higher stiffness and bearing capacity than that placed in an elliptical shape. The performance of the geocell-reinforced base depended on the elastic modulus of the geocell sheet. The unconfined geocell had a lower stiffness but a higher ultimate load capacity than the confined geocell. The benefit of the geocell was minimized when the infill material, quarry waste with apparent cohesion, was used as compared with the Kansas River sand without apparent cohesion. The single geocell-reinforced base had a lower stiffness and bearing capacity than the multiple geocell-reinforced base.
This paper presents the results of laboratory model loading tests and numerical studies carried out on square footings supported on geosynthetic reinforced sand beds. The relative performance of different forms of geosynthetic reinforcement (i.e. geocell, planar layers and randomly distributed mesh elements) in foundation beds is compared; using same quantity of reinforcement in each test. A biaxial geogrid and a geonet are used for reinforcing the sand beds. Geonet is used in two forms of reinforcement, viz. planar layers and geocell, while the biaxial geogrid was used in three forms of reinforcement, viz. planar layers, geocell and randomly distributed mesh elements. Laboratory load tests on unreinforced and reinforced footings are simulated in a numerical model and the results are analyzed to understand the distribution of displacements and stresses below the footing better. Both the experimental and numerical studies demonstrated that the geocell is the most advantageous form of soil reinforcement technique of those investigated, provided there is no rupture of the material during loading. Geogrid used in the form of randomly distributed mesh elements is found to be inferior to the other two forms. Some significant observations on the difference in reinforcement mechanism for different forms of reinforcement are presented in this paper.
Review of literature on the problem of bearing capacity of shallow foundations. It is shown that the greatest shortcoming of available theories lies in their unreserved assumption of incompressibility of the foundation soil. An attempt is made to formulate the rational compressibility criteria for soils subjected to foundation loads. An analysis of the effects on bearing capacity of roughness and vertical profile of foundation base, ground-water table, presence of adjacent footingjs and rate of loading.
This paper describes a series of laboratory model tests performed on strip footings supported on 3D and planar geotextile-reinforced sand beds under a combination of static and repeated loads. Footing settlement due to initial static applied load and up to 20,000 subsequent load repetitions was recorded, until its value becomes stable or failure occurred due to excessive settlement. The response under the first few cycles was found to be a significant behavioral characteristic of footings under repeated loads. The influence of various amplitudes of repeated load on foundations containing different numbers of planar geotextile layers and different heights of the 3D geotextile reinforcement were investigated. Most of the observed responses show plastic shakedown developing – that is a stable, resilient response is observed once incremental plastic strains under each load repetition have ceased to accumulate. The results show that the maximum footing settlement due to repeated loading is comparable for either planar- or 3D-reinforced sand and much improved over the settlement of unreinforced sand. The efficiency of reinforcement in reducing the maximum footing settlement was decreased by increasing the mass of reinforcement in the sand. On the whole, the results indicate that, for the same mass of geotextile material used in the tests, the 3D geotextile reinforcement system behaves more effectively than planar reinforcement as a retardant for the effects of dynamic loading. Thus, a specific improvement in footing settlement can be achieved using a lesser quantity of 3D geotextile material compared to planar geotextile.
This paper presents the results from laboratory-model tests on a strip footing supported by a sand bed reinforced with a geocell mattress. The parameters varied in the testing program include pattern of geocell formation, pocket size, height and width of geocell mattress, the depth to the top of geocell mattress, tensile stiffness of the geogrids used to fabricate geocell mattress and the relative density of the sand. With the provision of geocell reinforcement, failure was not observed even at a settlement equal to 50% of the footing width and a load as high as 8 times the ultimate bearing capacity of the unreinforced sand. Based on the model test results, the depth of placement and the dimensions of the geocell layer for mobilising maximum bearing capacity improvement have been determined. In addition to the tensile strength of reinforcement, the aperture size and orientation of ribs of the geogrid used to fabricate geocell mattress must be taken into account while evaluating its contribution to the improvement in the performance.
A novel technique to improve the load-deformation performance of thin soil cover layers over flexible long span soil-steel bridge conduits is proposed. The soil cover is reinforced by a composite layer of geocell-soil whose properties have greater strength and stiffness than the aggregate soil infill in an unreinforced condition. The paper describes a series of numerical simulations using a large strain non-linear finite element model to investigate the load-deformation response of midspan and eccentrically loaded steel conduits with and without reinforced geocell-soil covers. The simulation results show that the performance of soil-conduit systems with a conventional 1 m thick cover soil may be significantly improved by introducing a single layer of geocell-soil material. Alternatively, thinner depths of soil cover are possible using this reinforcement technique compared to conventional unreinforced methods.
The potential benefits of providing geocell reinforced sand mattress over clay subgrade with void have been investigated through a series of laboratory scale model tests. The parameters varied in the test programme include, thickness of unreinforced sand layer above clay bed, width and height of geocell mattress, relative density of the sand fill in the geocells, and influence of an additional layer of planar geogrid placed at the base of the geocell mattress. The test results indicate that substantial improvement in performance can be obtained with the provision of geocell mattress, of adequate size, over the clay subgrade with void. In order to have beneficial effect, the geocell mattress must spread beyond the void at least a distance equal to the diameter of the void. The influence of the void over the performance of the footing reduces for height of geocell mattress greater than 1.8 times the diameter of the footing. Better improvement in performance is obtained for geocells filled with dense soil.
The effect of rubber membrane on the measured triaxial compression strength of clay samples Fast Lagrangian Analysis of Continua (FLAC3D 4.00) Itasca Consulting Group Inc Behavior of geocell reinforced sub-ballast subjected to cyclic loading in plane strain condition
- D J Henkel
- G D Gilbert
- Asce
- Gt
Henkel, D.J., Gilbert, G.D., 1952. The effect of rubber membrane on the measured triaxial compression strength of clay samples. Geotechnique 3 (1), 20e29. Itasca, 2008. Fast Lagrangian Analysis of Continua (FLAC3D 4.00). Itasca Consulting Group Inc, Minneapolis, USA. Indraratna, B., Biabani, M., Nimbalkar, S., 2014. Behavior of geocell reinforced sub-ballast subjected to cyclic loading in plane strain condition. J. Geotech. Geo-environmental Eng. http://dx.doi.org/10.1061/(ASCE)GT.1943-5606.0001199.
Soil compressibility as determined by odometer and triaxial tests
- Janbu
Janbu, N., 1963. Soil compressibility as determined by odometer and triaxial tests.
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Uniaxial compressive behaviour of scrap-ped tire and sand filled wire netted geocell with a geotextile envelop Effects of geocell confinement on strength and deformation behaviour of gravel Numerical modelling of behavior of railway bal-lasted structure with geocell confinement
- S Lambert
- F Nicot
- P Gotteland
- B Leshchinsky
- H Ling
Lambert, S., Nicot, F., Gotteland, P., 2011. Uniaxial compressive behaviour of scrap-ped tire and sand filled wire netted geocell with a geotextile envelop. Geotext. Geomembr. 29, 483e490. Leshchinsky, B., Ling, H., 2013a. Effects of geocell confinement on strength and deformation behaviour of gravel. J. Geotech. Geoenvironmental Eng. 139 (2), 340e352. Leshchinsky, B., Ling, H., 2013b. Numerical modelling of behavior of railway bal-lasted structure with geocell confinement. Geotext. Geomembr. 36, 33e43. Latha, G.Madhavi, 2000. Investigations on the Behaviour of Geocell Supported Embankments (Ph.D. thesis submitted to Department of Civil Engineering, In-dian Institute of Technology Madras, Chennai).
Effect of reinforcement form on the bearing capacity of square footing on sand Numerical study on stability analysis of geocell reinforced slopes by considering the bending effect
- G Latha
- Madhavi
- A Somwanshi
Latha, G.Madhavi, Somwanshi, A., 2009. Effect of reinforcement form on the bearing capacity of square footing on sand. Geotext. Geomembr. 27, 409e422. Mehdipour, Iman, Ghazavi, Mahmoud, Moayed, R.Z., 2013. Numerical study on stability analysis of geocell reinforced slopes by considering the bending effect. Geotext. Geomembr. 37, 23e34.
Department of Civil Engi-neering Numerical simulations of sand and clay. Ground Improv Bearing capacity of circular footing on geocell sand mattress overlying clay bed with void Design and construction of geocell foundation to support embankment on soft settled red mud
- M S Raji
- S Gowrisetti
- T G Sitharam
- A J Puppala
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- S Sireesh
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