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Tensile load-uplift diagram of half-bulb and full-bulb underreamed piles and uniform cross-section pile of the same volume and length (L/d=12)
Source publication
In this study, the performance of underreamed piles in clayey soils has been evaluated.
Underreamed piles are deep in-situ concrete piles with one or more enlargements in their
stems. The enlargement is called bulb and increases the strength and stability of these piles.
The goal of this study was comparing the performance of half-bulb and full-...
Contexts in source publication
Context 1
... to Figures 8 and 10, it can be found that half-bulb underreamed pile has a superior performance than full-bulb underreamed pile as well as uniform cross-section pile of the same volume and length in both compressive and tensile loads. This is while the volume of full bulb is nearly two times larger than the half-bulb. ...
Context 2
... results showed that the use of half-bulb underreamed pile was better in comparison with the other pile types, especially in tensile bearing capacity in clay. Figures 8 and 10 show the results of these data. In Figure 9, deformation shading of a half-bulb underreamed pile has been presented. ...
Context 3
... to Figures 8 and 10, it can be found that half-bulb underreamed pile has a superior performance than full-bulb underreamed pile as well as uniform cross-section pile of the same volume and length in both compressive and tensile loads. This is while the volume of full bulb is nearly two times larger than the half-bulb. ...
Context 4
... results showed that the use of half-bulb underreamed pile was better in comparison with the other pile types, especially in tensile bearing capacity in clay. Figures 8 and 10 show the results of these data. In Figure 9, deformation shading of a half-bulb underreamed pile has been presented. ...
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Citations
... George et al. [5] and Vali et al. [6] numerically analyzed the performance of under-reamed piles under axial loading to estimate compression and uplift capacity. Farokhi et al. [7] did a numerical analysis to optimize the performance of under-reamed piles by changing the bulb shapes to full bulbs and half bulbs. Significant studies had also utilized FEM to figure out various behavior of under-reamed piles like uplift capacity of under-reamed piles in clay with linearly increasing cohesion [8]; the effect of scouring on lateral response of underreamed piles embedded in soft clay [9]; behavior of under-reamed piles under a compression load in clay [10]. ...
This study aims to investigate the performance of under-reamed piles under vertical harmonic vibration. A 3D finite element model has been developed and the effect of geometrical features of pile like aspect ratio, number of bulbs, and bulb spacings are being explored in this study. Under-reamed piles having a stem diameter of 0.2 m and bulb diameter of 0.5 m, under eccentric moments of 0.005 kg-m, 0.01 kg-m, and 0.02 kg-m were considered. Variations of geometries included length of the pile (4 m, 5 m, and 6 m), aspect ratios (20, 25, and 30), number of bulbs from 1 to 3, and bulb spacing (0.5 m, 0.75 m, and 1 m). The study concluded that an increase in length and bulb numbers highly influenced the performance of under-reamed piles by reducing amplitude to a better extent. However, an increase in spacing between bulbs exhibits negligible variations in resonant amplitude when subjected to dynamic loading.
... The bells contribute to distributing the loads in soil and increasing the piles' bearing capacity under both pullout and compressive loadings [2]. Belled-piles foundations are used in the ground with problems such as black cotton clay, which swells and shrinks excessively and varies depending on moisture levels [3]. Moreover, the bells also increase the bearing capacity of piles. ...
... Another issue in the design of under-reamed piles is optimizing this type of pile and calculating the thickness and shape of bulb formed in these piles. According to the findings of Farokhi et al., a pile with a half bulb placed at the bottom of the pile performs better under tension and compression than a full bulb pile, carrying 13% more load under compression than a full bulb and 73% more than a CS pile [6]. On the other hand, other methods for reinforcing the foundation have been suggested in recent years, with reinforcement columns being one of the most widely used. ...
One technique for increasing foundation bearing capacity, reducing settlement, and preventing liquefaction is jet grouting columns. Rock and soil cutting by jet became the basis for this technique, which has since developed into one of the most popular choices. The type of soil, the method of application, and the amount of cement used are just a number of the factors that influence the diameter and resistance of the column in this method, for example if this method is implemented in granular soil, the column has greater resistance and diameter than clay soils. One of the challenges of this method that engineers face in many projects is the existence of soil with various layers. This paper used numerical analysis to investigate the effect of increasing the diameter and resistance of the jet grouting column in sand lenses in clay layers. Geotechnical data from a project in the south of Iran, was utilized to investigate this topic. In order to check the performance and compare the jet grouting columns by enlargement with regular columns, two measures of reducing the execution time for the same cement consumption and the amount of settlement for the same number of columns were investigated.
... Under-reamed piles are cast-in-place concrete piles having one or more under-ream bulbs along their stems, which enhances pile capacity under compression and tension loads [1]. These piles can lessen the impact of negative skin friction and enhance tip resistance and pile shaft friction [2]. ...
Civil engineering is an important branch and always making human life safe and cheerfull. Researchers in the field of civil engineering are always enthusiastic and trying to overcome various challenges by providing advance solutions. The scope of civil engineering has widen considerably and it is demand of society to get better solutions through scientific research in various horizons of civil engineering. The better and durable structures, pleasant and healthy environment, better transport and automation to assist construction are some important topics included in this books through six chapters.
... The belled inclination angle has little influence on uplift bearing capacity and load-displacement curves (Liu et al., 2020).(Jebur et al., 2020) proved that the full sphere as the bell shape is the worst choice, as it has few effects on the distribution of vertical displacement.(Farokhi et al., 2014) showed that the half-cone bell of the belled pile had better performance than the other piles and had a higher ultimate tensile and compressive bearing capacity and lower displacement.(Engin et al., 2008; Majumder and Chakraborty, 2021; AL-Shamaa et al., 2021) proved that using belled piles in clayey soil is more effective than equal se ...
Multi-belled piles are piles with enlarged ends; these piles have one or further bells at the lower third part of the pile. These piles are suitable for many soils with problems such as softening clay, the variation of groundwater table, expansive soils, black cotton soil, and loose sand. The current study reviewed the behavior of belled piles in multi-layer soils subjected to axial compression and pullout loading. The review covered the experimental and theoretical works on belled piles in multi-layered soils. These piles were subjected to static and dynamic loadings in compression and pullout cases. Most theoretical results focused on software such as PLAXIS 3D. The axial load applied on the piles comes from the upper structure built above these piles, and negative skin friction comes from groundwater. The results obtained from previous studies showed the validity of using such piles in different types of soil and multilayer soils. According to previous studies, this study aims to find all the things about the belled piles, including the best shape of the belled pile being the half cone and the worst state being when the bell is fully cone. The best number of belled piles is two bells because the bearing capacity increases when the number of bells increases but does not exceed two due to hard work and high cost. The best location of a bell is at the base of the pile. The current study showed that the bearing capacity increased from 40% to 73.75% compared with ordinary piles.
... Farokhi et al. [10], numerically evaluated under-reamed piles in clayey soils and discovered that, when subjected to a tensile load, a half-bulb under-reamed pile has a larger maximum tensile bearing capacity than a full-bulb under-reamed pile and a uniform cross-section pile of the same dimension and volume. Moreover, the maximum pullout capacity of a full bulb was greater than that of a uniform cross-section pile of equal length and volume. ...
deformation behaviour of the under-reamed
pile under pullout loads.
• The bearing pullout load rises as the number
of bulbs increases.
• The maximum ultimate pullout capacity is
obtained in the case of the stiff clay resting
on the soft clay.
• The failure patterns of soil movement around
the projections were larger than those around
the shaft.
A 3D numerical model generated using PLAXIS-3D software was used in the
present research to predict the behavior of under-reamed piles under pullout
loading conditions with presumed soil Mohr-Coulomb failure. The under-reamed
pile was embedded in homogeneous, layered clay soil, with stiff clay overlain by
soft clay and soft clay overlain by stiff clay. The piles were chosen per the Indian
Code (IS 2911) specification, and two variables were studied: bulb provision and
soil layering. Inhomogeneous clay with varying cohesion values (20, 40, and 80
kPa) and under the same conditions, the pullout capacity was improved compared to a straight shaft (SP). The pullout capacity of the single bulb (SURP) increased once, while that of the double bulb (DURP) increased twice. The results revealed that anchoring the pile in a stronger stratum at a greater depth is advantageous when designing under-reamed pile foundations. In the case of stiff clay on top of soft clay, additional resistance against pullout is achieved, reducing the risk of pullout failure compared to soft clay in the upper layer
... Therefore, it is necessary to assess the undrained uplift capacity of the under-reamed pile in layered clayey soil. The research that has already contributed to the understanding on behaviour of under-reamed pile is reasonably addressed [1][2][3][4][5][6][7]. According to Martin and Stephen [1], a twin bulb under-reamed pile can be used as an alternate foundation for over consolidated hard clay. ...
Under-reamed piles are generally a choice of foundation for structures subjected to the uplift load; especially for the transmission line towers, patrolling towers, chimneys, tall and slender structures, etc. In the study, the undrained uplift capacity of single under-reamed pile embedded in layered clay is evaluated using finite element (FE) method-based software Plaxis 2D. The geometry of the under-reamed pile is chosen as per the standard codal provision. In the analysis, the soil is assigned with Mohr-Coulomb model and pile is assigned with Linear Elastic model. The thickness of layered clays i.e., soft clay overlain hard clay and hard clay overlain soft clay is varied with cohesion ratio = 2. The FE results are compared with the solutions available in the literature. The uplift capacity ratio defined as ultimate uplift capacity of under-reamed pile in single clay to that in layered clay having different clay layer thickness ratio (h/H = 0 to 1) are evaluated. The present study results are represented as design charts so as to be used in the design practice.
... Several studies (Mohan and Chandra 1961;Sowa 1970;Meyerhof and Sastry 1978;Martin 2001;Houlsby and Martin 2003;Kumar 2009, 2011) are available in the literature for the determination of the bearing and the uplift capacity of the piles without underream in clay. Limited studies (Martin and De Stephen 1983;Annie Peter, Lakshmanan, and Devadas Manoharan 2006;Shrivastava and Bhatia 2008;Farokhi, Alielahi, and Mardani 2014;George and Hari 2016;Vali et al. 2017) were performed with regard to the determination of the capacity of the underreamed piles in clay, especially for the uplift condition. The study reported by Martin and De Stephen (1983) concluded that the under-reamed piles with two bulbs were the suitable alternative foundation for the overconsolidated stiff clay. ...
The present study deals with the determination of the uplift capacity for an under-reamed pile in clay, whose cohesion increases linearly with depth, by following the finite element analysis methodology. The analysis was performed for: i) pile without under-ream, ii) single under-reamed pile and iii) double under-reamed pile. The geometry of the pile was selected following the relevant Indian standard code, and the analysis was performed for the different values of linearly increasing cohesion and for the various shaft adhesion. The safe and collapse load determined from the load-deformation curve indicated that its magnitude was highest for the double under-reamed pile followed by the single under-reamed pile. For the selected range of the embedment depth and the linearly increasing cohesion, the safe load for the single and the double under-reamed pile was found about 396% and 547% respectively higher than the pile without any under-ream.
... The financial cost budget, if so, for semi bulb of under reamed piles construction is considered less than that of a complete-bulb one as pointed out by Niroumand et al. [10]. The bearing capacity for compression of under reamed pile of semi-bulb is said to be about 13% and 73% has larger than that of complete bulb and pile of uniform cross-section respectively of the similar volume and length for the same volume and length as well stated by Ataollah et al. [6]. The research presented by Al-Taie [5] on deferent soil profiles show up in the center and south of Iraq which consists from top-upper layer of soft clay with thickness ranging between (2-15) m and dense sand or stiff clay of depth ranging between (5-20) m. ...
Landscapes and real estates are becoming very expensive day after day incorporated with the explosive increase in populations. Leaving a property estate due to poor soil engineering properties is not an option today. This will open tremendous doors to find solutions to increase the bearing capacity, reducing settlement by increasing soil strength properties. The trend of solutions can go in two directions, one direction as to stabilize in-situ soil, while the other goes into changing foundation configuration such as to use deep instead of shallow foundation and using the screw piles will settle into the second option. Using the helix piles is rather considered a fresher technique compared to the conventional piles. The mechanism of the screw piles is complicated same as the ordinary piles, but with the same objectives. This research is concerned to show the improvement obtained in using the helix and bulb pile techniques in improving the carrying capacity of conventional piles in soft clay. As such a laboratory model is utilized having dimensions of 30cm diameter and 55cm height. Three types of piles (screw, conventional and bulb) are used in this study. Test results reveal that by far the helix-type pile is more superior in providing higher bearing load capacity and stiffness compared to the bulb piles and the conventional ones. Double-helix increased the load capacity compared to conventional pile by about six times, for single about 3.5 times measured at limiting values. For stiffness 10 times and 6 times are recorded. Double bulb increased loading capacity by 3.5 times and 2 times for single bulb. About stiffness, the increase is 2.5 and one time respectively.
... Several studies have been conducted to assess the efficiency of under-reamed piles, particularly with uplift loads [8][9][10][11][12]. Martin and De Stephen [8] reported that for overconsolidated stiff clay, a foundation of under-reamed piles with two bulbs is an acceptable option. ...
Under-reamed piles with one or more bulbs have been widely used in almost all types of soil to support a range of structures. In some cases, in addition to vertical compressive or uplift loads, piles must withstand a considerable lateral load. A 3-D finite element study using ABAQUS software was conducted to examine the behavior of under-reamed piles in clay soil under pure lateral, pure uplift, and combined uplift and lateral loads. In this study, pile (L/D) ratios of 11.66, 15, 20, and 25 were considered by adjusting the pile length to simulate the behavior of rigid and flexible piles. The piles were modeled as a linear elastic material, and the soil behavior was simulated using the Drucker-Prager constitutive model. The findings show that the lateral resistance of piles with (L/D) ratios of 11.66 and 15 increased slightly when under-reamed piles were used. However, no change in lateral resistance was observed for under-reamed piles with (L/D) ratios of 20 and 25 compared with straight piles. The uplift capacity of under-reamed piles was significantly greater than that of a straight pile. The lateral capacity was marginally influenced by the prior uplift loading, such that it decreased for a rigid under-reamed pile, and increased for a flexible under-reamed pile.
