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Abstract

Reinforced soil walls are cost-effective alternatives to earth-retaining structures which can accommodate more settlements than conventional retaining wall systems. Ideally, freely draining granular materials such as sand are used as the backfills. But, scarcity of ideal granular materials necessitated the researchers to explore other alternatives. A large quantity of construction and demolition waste (CDW) is being generated in India as well as in other parts of the world. In this study, the feasibility of using CDW as a backfill for geosynthetic-reinforced soil walls has been attempted. The geotechnical properties of CDW were determined in order to ascertain whether their properties comply with existing specifications. It was observed that the geotechnical properties of CDW meet the requirements of an ideal backfill material for MSE walls mandated by various standards. Further, the numerical studies were conducted to study the deformation behavior of reinforced soil wall with CDW backfill immediately after construction. The assumptions made in the conventional design regarding the failure mechanism were also investigated. The paper highlights the potential use of processed CDW as a sustainable backfill material for reinforced walls.

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... Literatürde geosentetik donatılı istinat duvarlarının 2 ve 3 boyutlu stabilite analizlerine, tasarım parametrelerinin optimizasyonuna, sismik performans ve sismik tasarımı etkileyen parametreler üzerine, maliyet optimizasyonu üzerine, geosentetik duvar ve zemin davranışlarının nümerik analizlerine, performansını artırmaya yönelik tasarım önerilerine, laboratuvar modellerine ilişkin olarak çok sayıda çalışma yer almaktadır . Geosentetik donatılı istinat duvarlarını sürdürülebilirlik açısından irdeleyen ve geleneksel geri dolgular yerine inşaat atıkları gibi çeşitli sürdürülebilir malzemelerin kullanımını öneren bazı çalışmalar da mevcuttur [27,28]. Bazı araştırmacılar ise geosentetik donatılı duvarların karayolu, demiryolu gibi alanlardaki çeşitli uygulamalarına dikkat çekmişlerdir [29,30] Tekstil ürünlerin yumuşak zeminlerde karayolu inşasında bir yardımcı eleman olarak kullanımına ilişkin en eski örnekler dokuma kamış örtülerin eski Romalılar tarafından kullanılması olarak gösterilebilmektedir. Günümüz tekniklerine benzer şekilde, bu örtüler bataklık zemin üzerine serilerek üzeri taş ile kaplanmıştır. ...
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Article
Embankment is a frequently encountered application in road and railway constructions. In this study, reinforced concrete retaining wall, which is one of the traditional engineering structures and constructed to provide fill stabilization, and geosynthetic (geogrid) reinforced retaining structure were analyzed comparatively by considering cost, construction time, duration for service, service life, and aesthetics criteria. The comparisons were carried out on the engineering structures in two different locations on the same highway, which are under responsibility of the General Directorate of Highways (KGM). In the first location, a reinforced concrete retaining wall was designed instead of the existing geosynthetic reinforced wall, while a geosynthetic reinforced wall was designed instead of the existing reinforced concrete retaining wall in the second location. Cost analyses were made in line with KGM items. It was concluded that geosynthetic reinforced earth walls became advantageous in terms of cost, especially in parallel with the increase in height. In addition, it is revealed that geosynthetic reinforced walls are more advantageous when their performance is evaluated in terms of construction time, duration for service, service life and aesthetics criteria. It is thought that the data obtained from results of the study will contribute decision makers to decide the most appropriate engineering structure in terms of both performance and cost at the locations where filling stability problems arise in highway construction.
... Therefore, C&DW sorting, processing and reuse efforts should be stepped up to reduce this illegal dumping as well as increase the development of C&DW recycling plants. The authors make various efforts to reuse C&DW including investigating C&DW experimentally as well as numerically to know the viability of using C&DW as an alternate material of backfill soil for the reinforced retaining walls to reuse efforts [5,6]. Santos et al. [7] also make effort to reuse C&DW as an alternative material to backfill of a geogrid reinforced retaining wall constructed on a collapsible foundation, and all the investigation was done on a wrapped-face geosynthetic reinforced soil wall. ...
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Article
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Article
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The utilization of industrial and construction wastes has become necessary to avoid over-exploitation of natural resources. Steel slag and construction and demolition wastes (CDW) are two such materials explored in the present study for possible geotechnical applications. The performance of the waste materials has been compared to that of conventional fill material sand. A series of static triaxial tests were performed on unreinforced as well as geogrid reinforced dense specimens by applying different confining pressures. The stress–strain response, stiffness, particle breakage and energy absorption capacity of the materials were assessed. Slag exhibited the highest shear strength of all materials. On the other hand, CDW was found to sustain larger strain at failure. Inclusion of geogrid significantly enhanced the apparent cohesion, peak strength, axial strain at failure and the energy absorbing capacity of the materials. However, marginal change in friction angle was obtained. The particle breakage measurements revealed negligible breakage in slag and CDW materials. The triaxial stress–strain response of the materials was further used to back-calculate plastic hardening model parameters. The derived model parameters resulted in fairly accurate estimation of stress–strain response upon its implementation in finite difference package FLAC2D.
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Article
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The feasibility of substitute building materials (SBMs) in engineering applications was investigated within the project. A geogrid-reinforced soil structure (GRSS) was built using SBM as the fill material as well as vegetated soil for facing and on top of the construction. Four different SBMs were used as fill material, namely blast furnace slag (BFS), electric furnace slag (EFS), track ballast (TB), and recycled concrete (RC). For the vegetated soil facing, a mixture of either recycled brick (RB) material or crushed lightweight concrete (LC) mixed with organic soil was used. The soil mechanical and chemical parameters for all materials were determined and assessed. In the next step, a GRSS was built as a pilot application consisting of three geogrid layers with a total height of 1.5 m and a slope angle of 60°. The results of the soil mechanical tests indicate that the used fill materials are similar or even better than primary materials, such as gravel. The results of the chemical tests show that some materials are qualified to be used in engineering constructions without or with minor restrictions. Other materials need a special sealing layer to prevent the material from leakage. The vegetation on the mixed SBM material grew successfully. Several ruderal and pioneer plants could be found even in the first year of the construction. The porous material (RB and LC) provide additional water storage capacity for plants especially during summer and/or heat periods. With regard to the results of the chemical analyses of the greening layers, they are usable under restricted conditions. Here special treatment is necessary. Finally, it can be stated that SBMs are feasible in GRSS, particularly as fill material but also as a mixture for the greenable soil.
Article
The scarcity and fast depletion of granular materials necessitated to find alternative backfill materials in MSE walls. In the present study, application of construction and demolition waste (CDW) as a backfill for MSE walls was investigated. The physical, chemical, hydraulic and mechanical properties of CDW were found to meet the requirements of ideal backfills mandated by various design standards of MSE walls. At the end of construction, maximum facing deformation was at lower one-third height of the wall for MSE wall resting on a firm foundation. Influence of yielding foundation on the performance of MSE wall was also studied by varying the distortion levels to 0.2, 0.4 and 0.6. At the onset of differential settlements, the location of maximum facing deformation changed to the bottom of the wall. The maximum facing deformation and axial strain increased by 15 times and 2.5% respectively, when the wall underwent a distortion of 0.6.
Chapter
Seasonal variations in the soil moisture content can result in significant changes in soil suction. Rainfall infiltration can cause loss of matric suction in the unsaturated lateritic soil. Several failures are reported in lateritic soil slopes in Kerala, associated with rainfall. Geosynthetics are generally used for improving the stability of soil structures constructed with poorly draining soils. Shear strength at the interface of unsaturated lateritic soil with geosynthetics plays a crucial role on the internal stability of geosynthetics reinforced structures. The present study investigates the influence of rainfall-induced wetting on shear strength of lateritic soil and lateritic soil-geosynthetics interface. Lateritic soil was collected from a site in Kerala, which was subjected to rainfall-induced slope failure. Geotechnical characterization of the soil was carried out. Shear testing was conducted on soil samples of size 305 × 305 × 200 mm. When the moisture content was increased by 4% due to wetting, the shear strength of the lateritic soil was reduced by 20%. In contrast, the corresponding reduction in strength at the interface for the soil–geosynthetic system was only 3%. Similarly, an increase in moisture content by 8% due to wetting resulted in a reduction in strength by 30% and 4% for soil–soil and soil–geosynthetic systems, respectively.
Chapter
With the advent of ever-growing urbanization and industrialization, there exists a requirement for heavy infrastructures that can retain heavy earth masses and are sustainable in its functioning. The conventional earth mass retention methods using rigid retaining walls are not preferred for most of the projects, as they are expensive and are time-consuming for the construction when compared to the recently developed methods of earth mass retention by Mechanically Stabilized Earth (MSE) structures. MSE walls having large height when constructed in a single tier, often require a huge volume of excavation and an effective land area which is impossible to attain every time. Therefore, the most suitable alternative is to construct it in a tiered fashion. The tiered MSE walls can tolerate large differential settlements without distress, give a sound performance, are aesthetically appealing, are cost-effective, convenient, and provide simplicity in construction. However, the configuration of such walls may present several engineering challenges that have not been covered by the conventional design methods and calculations. This study aims to assess the performance and response of a multi-tiered 12 m high (H) MSE wall and compare it with a single-tiered MSE wall through numerical solutions based on finite element modeling. From the outcomes of this study, it is found that the normalized maximum lateral displacement of the facing of the wall (Δ/Η) is 5.4% and 1.71% in the single-tiered and three-tiered wall system respectively. Also, the factor of safety in three-tiered and single-tiered wall systems observe a growth of 9.4% and 8.4% respectively when the reinforcement length is increased, which establishes the improved performance of the tiered MSE walls and justifies its usage in place of single-tiered MSE walls.
Chapter
The land scarcity has built up the pressure on the engineers to bring a cost-effective and time-saving solution to utilize the ground with poor strength as a foundation bed for various structures. With the recent progress in the area of ground reinforcing techniques using geosynthetics, the extensive usage of geotextile materials as a reinforcing element in the soil to strengthen the load-bearing capacity of the soil mass and reducing the anticipated settlement of the footing pushes the researchers to evolve new methods to maximize the advantages received from the reinforced earth beds. In the above context, the provision of reinforcing layers with wraparound ends has brought additional improvement in the load settlement behavior of a strip footing resting over such reinforced soil mass but this recently developed technique lacks the appropriate guidelines/recommendations for the geometrical configuration parameters of the reinforcing layer to maximize the benefit from the reinforcing layer. Given the above, a comprehensive numerical study has been conducted to propose some recommendations on the geometrical configurations of the reinforcing layers. Furthermore, this study also investigates the influence of the geogrid–soil interface on the load-settlement response of the reinforced bed under vertical footing load. From the findings of the study, it is concluded that the width of the geogrid layers, governs the overall load-bearing capacity of the reinforced soil mass system, besides it, also suggests an optimum width of the geogrid layers, which equals 1.5 times the width of the footing should be used to maximize the effective utilization of the wraparound technique. Furthermore, it was also noted that appropriate assessment of the interface between soil and geogrid may bring an optimized design of the reinforced soil mass as a foundation bed for the footings.
Article
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Construction and associated demolition processes produce huge amount of solid waste, generally termed as construction and demolition waste (CDW). Management and proper disposal of these wastes is an area of prime concern for modern civil engineers. About 90% of all CDW is composed of building derived materials (BDM) obtained from concrete, bricks, and tiles from structural and non-structural elements of a building. The present study emphasizes on the use of virgin BDM, which conserves natural aggregate, reduces the impact on landfills, saves energy, and thus can provide significant cost benefit. Five types of BDM—crushed lightweight concrete (T1), crushed marble tiles (T2), crushed high strength concrete (T3), crushed normal portland cement concrete (T4), and crushed bricks (T5)—are characterised to assess their compatibility when used in conjunction with local soil. The soil, BDM and soil–BDM mixes are characterized from physical, mechanical, mineralogical, microstructural, and chemical aspects. These tests are then repeated for the aforementioned soil-BDM mixes after immersion in acids. Aggregate impact value (AIV) results on the five types of BDM indicate that T1 and T5 are poorly resistant to impact loads. However, T2, T3, and T4 show relatively better resistance to impact loads and satisfy the requirements for sub-base material standards. Shear strength studies show that the average optimum replacement of soil by BDM is in the range of 17–23% by mass. In order to test the compatibility of BDM in soils containing aggressive chemicals, the properties mentioned above are re-evaluated after exposing the BDM to aggressive chemical environments. The results indicate that the internal angle of friction (ϕ) of virgin BDM is found to vary significantly due to acid attack. The results of AIV after exposing the BDM to acids show that BDM are highly susceptible to chemically aggressive environment. The performance of all types BDM are affected by the presence of acids and appropriate measures must be adopted while using BDM in such chemically aggressive environment. These standards can be used as guidelines in the present study in the absence of specific standards for BDM applications.
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The interface shear strength properties of geogrid-reinforced recycled construction and demolition (C&D) materials were determined in this research to assess the viability of using geogrid-reinforced C&D materials as alternative construction materials. The C&D materials investigated were recycled concrete aggregate (RCA), crushed brick (CB), and reclaimed asphalt pavement (RAP). Biaxial and triaxial geogrids were tested as the geogrid-reinforcement materials. The interface shear strength properties of the C&D materials were ascertained by using a large direct shear test (DST) equipment. Large-scale DST was conducted for unreinforced and geogrid-reinforced C&D materials. The interface peak and residual shear strength property of unreinforced and geogrid-reinforced RCA was found to be higher than that of CB and RAP. RAP was found to have the lowest interface shear strength properties of the C&D materials. The higher strength triaxial geogrids were found to attain higher interface shear strength properties than that of the lower strength biaxial geogrids. The DST results, however, indicated that the interface shear strength properties of the geogrid-reinforced C&D materials were less than that of the respective material without reinforcement. This can be attributed to the lack of interlock between the geogrids and the recycled C&D aggregates, as well as the current conventional testing method for DST that induces a shear plane at the boundary between the lower and upper boxes where the geogrid is placed. The unreinforced and geogrid-reinforced RCA, CB, and RAP were found to meet the peak and residual shear strength requirements for typical construction materials in civil engineering applications.
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The paper describes a numerical model that was developed to simulate the response of three instrumented, full-scale, geosynthetic-reinforced soil walls under working stress conditions. The walls were constructed with a fascia column of solid modular concrete units and clean, uniform sand backfill on a rigid foundation. The soil reinforcement comprised different arrangements of a weak biaxial polypropylene geogrid reinforcement material. The properties of backfill material, the method of construction, the wall geometry, and the boundary conditions were otherwise nominally the same for each structure. The performance of the test walls up to the end of construction was simulated with the finite-difference-based Fast Lagrangian Analysis of Continua (FLAC) program. The paper describes FLAC program implementation, material properties, constitutive models for component materials, and predicted results for the model walls. The results predicted with the use of nonlinear elastic-plastic models for the backfill soil and reinforcement layers are shown to be in good agreement with measured toe boundary forces, vertical foundation pressures, facing displacements, connection loads, and reinforcement strains. Numerical results using a linear elastic-plastic model for the soil also gave good agreement with measured wall displacements and boundary toe forces but gave a poorer prediction of the distribution of strain in the reinforcement layers.Key words: numerical modelling, retaining walls, reinforced soil, geosynthetics, FLAC.
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Article
Mechanical and hydraulic properties of recycled concrete aggregate (RCA) were evaluated for use as backfill in mechanically stabilized earth (MSE) walls. Large-scale drained triaxial tests, direct shear tests and pullout tests were performed to obtain mechanical properties of RCA interacting with various geosynthetics. Long-term filtration (LTF) tests were performed to evaluate hydraulic conductivity of RCA-geotextile systems. Results showed that the RCA had an internal friction angle of 49°, which was within the typical range. The RCA-uniaxial geogrid had the highest interface friction angle of 36° – and the interface friction angles of RCA-biaxial geogrid, RCA-nonwoven geotextile, and RCA-woven geotextile were 32°, 26° and 22°, respectively. Reinforced RCA showed comparable pullout capacity to reinforced sand. No slippage was observed between the RCA and geotextiles or geogrids, and the failures occurred mainly due to rupture of the geotextiles and geogrids during the pullout test. Results of the LTF tests showed that, over a filtration period of 2500 h, the ratio of mean hydraulic conductivity of RCA only to that of RCA-nonwoven geotextile and RCA-woven geotextile systems remained between 0.91 and 3.2, suggesting that the clogging of the geotextiles with RCA was minimal.
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The paper describes the interface behaviour of bottom ash, obtained from two thermal power plants, and geogrid for possible utilization as a reinforced fill material in reinforced soil structures. Pullout tests were conducted on polyester geogrid embedded in compacted bottom ash samples as per ASTM D6706-01. Locally available natural sand was used as a reference material. The pullout resistance offered by geogrid embedded in bottom ash was almost identical to that in sand. In order to study the influence of placement condition of the material on pullout resistance, test were conducted on uncompacted fill materials. Pullout resistance offered by geogrids embedded in uncompacted specimen reduced by 30–60% than that at the compacted condition.
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The use of construction and demolition (C&D) recycled materials in the construction industry represents an important step towards a more sustainable future and, simultaneously, represents a new market opportunity to be explored. In the last years, several case studies relating to the application of C&D recycled materials have emerged, mainly, in base and sub-base layers of the roadway infrastructures and in concrete production. This papers deals with the use of fine mixed recycled aggregates as filling material of geosynthetic reinforced embankments. The physical, mechanical and environmental characterization of C&D recycled materials is presented and discussed, as well as, the direct shear behaviour of two C&D materials/geosynthetic interfaces. The C&D recycled material was collected from a Portuguese recycling plant and comes from non-selected C&D wastes. One geogrid and one high strength geotextile were used to assess the interfaces behaviour. The environmental characterization of the C&D recycled material, carried out through laboratory leaching tests, has not shown any environmental concerns. Direct shear test results have revealed that the increase in C&D recycled material moisture content can measurably reduce the interface shear strength. The shear strength of the C&D material/geosynthetic interface has improved with the degree of compaction increase. The coefficients of interaction reached for C&D material/geosynthetic interfaces, a key factor in the design of geosynthetic reinforced structures, compare well with those found in the literature for soil/geosynthetic interfaces.
Article
Construction and Demolition Wastes (C&DW) are increasingly being reused in civil engineering applications, mainly in concrete production and base layers of roadway infrastructures. However, frequently the fine grain portion of these recycled aggregates is not considered suitable for those applications being landfilled instead of recycled. Moreover, the value-added utilisation of recycled C&DW in the construction of geosynthetic reinforced structures (steep slopes and retaining walls) is almost an unexplored field. This research assesses the feasibility of using fine-grain recycled C&DW as filling material of geosynthetic reinforced structures (GRS), appraising the physical, mechanical and environmental characterization of the construction and demolition material (C&DM), as well as, the direct shear and pullout behaviour of the interfaces between this material and three distinct geosynthetics (two geogrids and one geocomposite reinforcement or high strength geotextile). Direct shear tests results have shown that fine-grain recycled C&DW, properly compacted, exhibit similar shear strength to natural soils used commonly in the construction of GRS. The potential contamination of groundwater by these recycled C&DW was evaluated through laboratory leaching tests and, excepting the values of sulphate and total dissolved solids (TDS), this recycled C&DW complies with the provisions of European Council Decision 2003/33/EC for inert materials. High values of coefficients of interaction for C&DW/geosynthetic interfaces, a parameter of utmost importance in the design and performance of GRS, were achieved. The results herein presented support the viability of using these recycled C&DW as filling material for GRS construction.
Article
Mechanically stabilized earth (MSE) walls reinforced by geogrids and geotextiles have seen a tremendous growth over the past thirty years. However, along with this growth has come numerous failures consisting of excessive deformation and, in some cases, actual collapse. Of the 82-cases in the authors data base, improper drainage control was the cause in 68% of them. As a result, this paper is focused on both internal drainage issues within the reinforced soil mass within the reinforced soil mass (46%) and external drainage issues around the soil mass (22%). After a brief introduction of the technology some elements of traditional design will be presented. The issue of proper versus improper methods of drainage control will then form the core of the paper. A summary and recommendations section aimed at preventing drainage problems in the future will conclude the paper.
Article
The use of recycled aggregates (RA) in construction constitutes a significant step towards a more sustainable society and also creates a new market opportunity to be exploited. In recent years, several case-studies have emerged in which RA were used in Geotechnical applications, such as filling materials and in unbound pavement layers. This paper presents a review of the most important physical properties of different types of RA and their comparison with natural aggregates (NA), and how these properties affect their hydraulic and mechanical behaviour when compacted. Specifically, the effects of compaction on grading size distribution curves and density are analysed, as well as the consequences of particle crushing on the resilient modulus, CBR and permeability. The paper also contains an analysis of the influence of incorporating different RA types on the performance of unbound road pavement layers as compared with those built with NA by means of the International Roughness Index and deflection values. The results collected from the literature indicate that the performance of most RA is comparable to that of NA and can be used in unbound pavement layers or in other applications requiring compaction.
Article
The proper use of natural resources is one of the fundamental pillars of sustainable development imposed on modern societies. A more effective and efficient use of natural resources, as well as the mitigation of environmental impacts induced by their extraction could be achieved if proper management and recycling policies of Construction and Demolition (C&D) wastes were implemented. The valorisation of wastes in the construction industry is needed and is a way toward sustainability. This paper provides a literature review on studies related to the valorisation of Construction and Demolition (C&D) materials in geotechnical engineering applications, with an emphasis on their use as recycled aggregates in base layers of roadway infrastructures and as filling material for geosynthetic reinforced structures. Specifications that should be followed when these materials are used in such projects are also summarised. With this review it is intended to promote the use of recycled C&D materials, showing that research carried out all over the world has demonstrated their good performance in general.
Article
This study numerically evaluated the combined effects of different controlling factors (i.e., wall height, stresses induced during backfill compaction, reinforcement stiffness, toe conditions, and facing stiffness) on the behavior of geosynthetic-reinforced soil (GRS) walls under working stress conditions. The results were compared with values predicted by different currently used methods. It was shown that toe resistance has a major effect on the prediction capability of those design methods. Parametric analyses have shown that the amount of tension in the reinforcement varies with restraint at the base of the block facing. For free-base conditions with a constant value for reinforcement stiffness, the tension in the reinforcements was the same irrespective of the facing stiffness and the wall height. For the fixed-base conditions, the amount of tension in the reinforcements and horizontal toe load varied as a function of the facing stiffness. Comparing individual measurements of reinforcement tension verified the significant effect that the toe restraint has on the amount of tension mobilized in the reinforcements at the bottom of the wall. The results showed that the amount of tension in the reinforcement is a function of the magnitude of the compaction-induced stress and the reinforcement stiffness. These results indicate that the compaction-induced stress does not significantly affect the magnitude of the horizontal toe load.
Article
Geosynthetic reinforced soil walls are now an accepted technology for the solution of earth-retaining problems due to cost savings, easy and quick construction, and ssociated environmental benefits. Additional savings and reduction in environmental impact can be realised by using recycled construction and demolition waste (RCDW) as the backfill material. This paper describes two such structures that were built to full scale and instrumented. One of the walls was reinforced with a woven polyester geogrid (wall 1) and the other (wall 2) with a relatively more extensible nonwoven polypropylene geotextile. Both walls were constructed using RCDW as backfill material and were built on a foundation soil prone to fabric collapse due to increased stress and/or increase in moisture content. During the monitoring period the walls were subjected to a rainy season followed by induced inundation of the foundation to trigger soil fabric collapse. The results showed that foundation soil collapse influenced wall behaviour more than geosynthetic type. The exception to similar performance was local face bulging which was greater for wall 2 (geotextile) with the more extensible reinforcement under unconfined conditions than for wall 1 (geogrid) which was expected in the moving formwork construction method. However, directly behind the wall face where both reinforcement material types were confined the horizontal displacements were similar. In addition, at locations beyond half of the wall base length the strain distributions were low (1% or less) for both walls. A practical conclusion from this study is that if the wrap-face appearance at end of construction is not a concern (i.e. large bulging) then wall performance is unaffected by the choice of reinforcement types used in this investigation.
Article
This paper presents the findings of a laboratory investigation of the characterization of recycled crushed brick and an assessment of its performance as a pavement subbase material. The properties of the recycled crushed brick were compared with the local state road authority specifications in Australia to assess its performance as a pavement subbase material. The experimental program was extensive and included tests such as particle size distribution, modified Proctor compaction, particle density, water absorption, California bearing ratio, Los Angeles abrasion loss, pH, organic content, static triaxial, and repeated load triaxial tests. California bearing ratio values were found to satisfy the local state road authority requirements for a lower subbase material. The Los Angeles abrasion loss value obtained was just above the maximum limits specified for pavement subbase materials. The repeat load triaxial testing established that crushed brick would perform satisfactorily at a 65% moisture ratio level. At higher moisture ratio levels, shear strength of the crushed brick was found to be reduced beyond the acceptable limits. The results of the repeat load triaxial testing indicate that only recycled crushed brick with a moisture ratio of around 65% is a viable material for usage in pavement subbase applications. The geotechnical testing results indicate that crushed brick may have to be blended with other durable recycled aggregates to improve its durability and to enhance its performance in pavement subbase applications.
Article
This research was undertaken to investigate the suitability of recycled construction and demolition materials as alternative pipe backfilling materials for stormwater and sewer pipes. Three commonly found recycled construction and demolition waste materials, (crushed brick, recycled concrete aggregate and reclaimed asphalt pavement) were investigated to assess their suitability as a pipe backfilling material. The physical, geotechnical and chemical properties of these construction and demolition materials were compared with local engineering and water authorities specifications for typical quarried materials so as to assess their performance as a viable substitute for virgin quarried aggregates in pipe backfilling applications. Physical and geotechnical characterisation tests such as particle size distribution, specific gravity, water absorption, Los Angeles abrasion, California Bearing Ratio and modified Proctor compaction tests were undertaken. Chemical properties were also determined, including organic content, pH, trace element or total concentration and leachate testing of the construction and demolition materials for a range of contaminant constituents. In terms of physical, geotechnical and chemical assessment for pipe backfilling applications, recycled concrete aggregate and crushed brick were found to have the properties recommended by environmental protection authorities while reclaimed asphalt pavement material did not meet some of the specified requirements. Also shear strength properties were found to be equivalent or superior to those of typical quarry backfilling materials. This research indicates that traditional considered waste materials can be reused viably as alternate pipe backfilling materials.
Article
The paper describes the novel use of recycled construction and demolition waste (RCDW) material as the backfill material in an otherwise conventional 3.6-m high wrapped-face geosynthetic reinforced soil wall. The wall was constructed over a collapsible foundation soil which is common in the area around the capital city of Brasilia. The wall was instrumented and then monitored though dry and wet rainy seasons. The influence of cumulative rainfall on foundation compressibility was detectable and seasonal wetting and drying was shown to quantitatively influence wall deformations, settlement, horizontal earth pressures and reinforcement strains. Nevertheless, wall performance was judged to be satisfactory when compared to the performance of other walls of similar size constructed with traditional select granular soils over non-collapsible foundation soils. The results of this investigation demonstrate that significant project cost savings may be possible by avoiding more expensive traditional backfill materials and larger societal economic savings accrued by diverting RCDW waste streams from landfills.
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