The Experts below are selected from a list of 291 Experts worldwide ranked by ideXlab platform
Ridong Fan - One of the best experts on this subject based on the ideXlab platform.
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shmp amended ca bentonite Sand Backfill barrier for containment of lead contamination in groundwater
International Journal of Environmental Research and Public Health, 2020Co-Authors: Yuling Yang, Krishna R Reddy, Wenjie Zhang, Ridong FanAbstract:This study investigated the feasibility of using sodium hexametaphosphate (SHMP)- amended calcium (Ca) bentonite in Backfills for slurry trench cutoff walls for the containment of lead (Pb) contamination in groundwater. Backfills composed of 80 wt% Sand and 20 wt% either Ca-bentonite or SHMP-amended Ca-bentonite were tested for hydraulic conductivity and sorption properties by conducting laboratory flexible-wall hydraulic conductivity tests and batch isothermal sorption experiments, respectively. The results showed that the SHMP amendment causes a one order of magnitude decrease in hydraulic conductivity of the Backfill using tap water (1.9 to 3.0 × 10−10 m/s). Testing using 1000 mg/L Pb solution resulted insignificant variation in hydraulic conductivity of the amended Backfill. Moreover, SHMP-amendment induced favorable conditions for increased sorption capacity of the Backfill, with 1.5 times higher retardation factor relative to the unamended Backfill. The Pb transport modeling through an hypothetical 1-m-thick slurry wall composed of amended Backfill revealed 12 to 24 times of longer breakthrough time for Pb migration as compared to results obtained for the same thickness slurry wall with unamended Backfill, which is attributed to decrease in seepage velocity combined with increase in retardation factor of the Backfill with SHMP amendment. Overall, SHMP is shown to be a promising Ca-bentontie modifier for use in Backfill for slurry trench cutoff wall for effective containment of Pb-contaminated groundwater.
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SHMP-Amended Ca-Bentonite/Sand Backfill Barrier for Containment of Lead Contamination in Groundwater
International journal of environmental research and public health, 2020Co-Authors: Yuling Yang, Krishna R Reddy, Wenjie Zhang, Ridong FanAbstract:This study investigated the feasibility of using sodium hexametaphosphate (SHMP)- amended calcium (Ca) bentonite in Backfills for slurry trench cutoff walls for the containment of lead (Pb) contamination in groundwater. Backfills composed of 80 wt% Sand and 20 wt% either Ca-bentonite or SHMP-amended Ca-bentonite were tested for hydraulic conductivity and sorption properties by conducting laboratory flexible-wall hydraulic conductivity tests and batch isothermal sorption experiments, respectively. The results showed that the SHMP amendment causes a one order of magnitude decrease in hydraulic conductivity of the Backfill using tap water (1.9 to 3.0 × 10−10 m/s). Testing using 1000 mg/L Pb solution resulted insignificant variation in hydraulic conductivity of the amended Backfill. Moreover, SHMP-amendment induced favorable conditions for increased sorption capacity of the Backfill, with 1.5 times higher retardation factor relative to the unamended Backfill. The Pb transport modeling through an hypothetical 1-m-thick slurry wall composed of amended Backfill revealed 12 to 24 times of longer breakthrough time for Pb migration as compared to results obtained for the same thickness slurry wall with unamended Backfill, which is attributed to decrease in seepage velocity combined with increase in retardation factor of the Backfill with SHMP amendment. Overall, SHMP is shown to be a promising Ca-bentontie modifier for use in Backfill for slurry trench cutoff wall for effective containment of Pb-contaminated groundwater.
Nadarajah Ravichandran - One of the best experts on this subject based on the ideXlab platform.
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properties of shredded roof membrane Sand mixture and its application as retaining wall Backfill under static and earthquake loads
Recycling, 2017Co-Authors: Bennett Livingston, Nadarajah RavichandranAbstract:About 20 billion square feet of Ethylene Propylene Diene Monomer (EPDM) rubber is installed on roofs in the United States and most of them will be reaching the end of their lifespan soon. The purpose of this study is to investigate potential reuses of this rubber in Civil Engineering projects rather than disposing it into landfills. First, laboratory tests were performed on various shredded rubber-Sand mixtures to quantify the basic geotechnical engineering properties. The laboratory test results show that the shredded rubber-Sand mixture is lightweight with good drainage properties and has shear strength parameters comparable to Sand. This indicates that the rubber-Sand mixture has potential to be used for retaining wall Backfill and many other projects. To assess the economic advantage of using shredded rubber-Sand mixtures as a lightweight Backfill for retaining walls subjected to static and earthquake loadings, geotechnical designs of a 6 m tall gravity cantilever retaining wall were performed. The computed volume of concrete to build the structural components and volume of Backfill material were compared with those of conventional Sand Backfill. Results show significant reductions in the volume of concrete and Backfill material in both static and earthquake loading conditions when the portion of shredded rubber increased in the mixture.
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Properties of Shredded Roof Membrane–Sand Mixture and Its Application as Retaining Wall Backfill under Static and Earthquake Loads
MDPI AG, 2017Co-Authors: Bennett Livingston, Nadarajah RavichandranAbstract:About 20 billion square feet of Ethylene Propylene Diene Monomer (EPDM) rubber is installed on roofs in the United States and most of them will be reaching the end of their lifespan soon. The purpose of this study is to investigate potential reuses of this rubber in Civil Engineering projects rather than disposing it into landfills. First, laboratory tests were performed on various shredded rubber-Sand mixtures to quantify the basic geotechnical engineering properties. The laboratory test results show that the shredded rubber-Sand mixture is lightweight with good drainage properties and has shear strength parameters comparable to Sand. This indicates that the rubber-Sand mixture has potential to be used for retaining wall Backfill and many other projects. To assess the economic advantage of using shredded rubber-Sand mixtures as a lightweight Backfill for retaining walls subjected to static and earthquake loadings, geotechnical designs of a 6 m tall gravity cantilever retaining wall were performed. The computed volume of concrete to build the structural components and volume of Backfill material were compared with those of conventional Sand Backfill. Results show significant reductions in the volume of concrete and Backfill material in both static and earthquake loading conditions when the portion of shredded rubber increased in the mixture
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Applicability of shredded tire chips as a lightweight retaining wall Backfill in seismic regions
Geo-Congress 2014 Technical Papers, 2014Co-Authors: Nadarajah Ravichandran, Lea HugginsAbstract:Using shredded tires as an alternative Backfill material for retaining walls is an effective method for recycling a common and abundant waste material. In this paper, the engineering properties of the shredded tire from various sources were compiled. Retaining walls were designed for static and seismic conditions using the average properties following load and resistance factor design (LRFD) method and compared with that of conventional granular material. The performance of retaining wall Backfilled with shredded tires was then investigated by applying design earthquake acceleration-time histories using advanced finite element software and compared with that of Sand Backfill. Results show that the shredded tire Backfill significantly reduces the wall tip deflection and maximum shear force and bending moment along the wall.
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Numerical study on the dynamic behavior of retaining walls Backfilled with shredded tires
GeoRisk 2011, 2011Co-Authors: E. Huggins, Nadarajah RavichandranAbstract:Previous research has shown that shredded tires are a beneficial replacement for conventional Sand Backfills in retaining walls as they reduce both material costs and structural wall size requirements. To further investigate the suitability of tire shreds as a Backfill material, this study evaluates the performance of retaining walls Backfilled with tire shreds under dynamic loading conditions. Projected lateral earth pressures and bending moments and shear forces on the structure are evaluated for both shredded tire Backfill and conventional Backfill Sand using a geotechnical engineering finite element software, PLAXIS. Input information for material properties of soil, Sand Backfill, and shredded tires is determined from laboratory testing. Through this comprehensive dynamic simulation, the safety and performance of shredded tires is confirmed for structures under earthquake loading. This demonstrates the viability of shredded tires as an economical replacement for conventional Sand in the construction of retaining walls in seismic zones.
Yuling Yang - One of the best experts on this subject based on the ideXlab platform.
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shmp amended ca bentonite Sand Backfill barrier for containment of lead contamination in groundwater
International Journal of Environmental Research and Public Health, 2020Co-Authors: Yuling Yang, Krishna R Reddy, Wenjie Zhang, Ridong FanAbstract:This study investigated the feasibility of using sodium hexametaphosphate (SHMP)- amended calcium (Ca) bentonite in Backfills for slurry trench cutoff walls for the containment of lead (Pb) contamination in groundwater. Backfills composed of 80 wt% Sand and 20 wt% either Ca-bentonite or SHMP-amended Ca-bentonite were tested for hydraulic conductivity and sorption properties by conducting laboratory flexible-wall hydraulic conductivity tests and batch isothermal sorption experiments, respectively. The results showed that the SHMP amendment causes a one order of magnitude decrease in hydraulic conductivity of the Backfill using tap water (1.9 to 3.0 × 10−10 m/s). Testing using 1000 mg/L Pb solution resulted insignificant variation in hydraulic conductivity of the amended Backfill. Moreover, SHMP-amendment induced favorable conditions for increased sorption capacity of the Backfill, with 1.5 times higher retardation factor relative to the unamended Backfill. The Pb transport modeling through an hypothetical 1-m-thick slurry wall composed of amended Backfill revealed 12 to 24 times of longer breakthrough time for Pb migration as compared to results obtained for the same thickness slurry wall with unamended Backfill, which is attributed to decrease in seepage velocity combined with increase in retardation factor of the Backfill with SHMP amendment. Overall, SHMP is shown to be a promising Ca-bentontie modifier for use in Backfill for slurry trench cutoff wall for effective containment of Pb-contaminated groundwater.
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SHMP-Amended Ca-Bentonite/Sand Backfill Barrier for Containment of Lead Contamination in Groundwater
International journal of environmental research and public health, 2020Co-Authors: Yuling Yang, Krishna R Reddy, Wenjie Zhang, Ridong FanAbstract:This study investigated the feasibility of using sodium hexametaphosphate (SHMP)- amended calcium (Ca) bentonite in Backfills for slurry trench cutoff walls for the containment of lead (Pb) contamination in groundwater. Backfills composed of 80 wt% Sand and 20 wt% either Ca-bentonite or SHMP-amended Ca-bentonite were tested for hydraulic conductivity and sorption properties by conducting laboratory flexible-wall hydraulic conductivity tests and batch isothermal sorption experiments, respectively. The results showed that the SHMP amendment causes a one order of magnitude decrease in hydraulic conductivity of the Backfill using tap water (1.9 to 3.0 × 10−10 m/s). Testing using 1000 mg/L Pb solution resulted insignificant variation in hydraulic conductivity of the amended Backfill. Moreover, SHMP-amendment induced favorable conditions for increased sorption capacity of the Backfill, with 1.5 times higher retardation factor relative to the unamended Backfill. The Pb transport modeling through an hypothetical 1-m-thick slurry wall composed of amended Backfill revealed 12 to 24 times of longer breakthrough time for Pb migration as compared to results obtained for the same thickness slurry wall with unamended Backfill, which is attributed to decrease in seepage velocity combined with increase in retardation factor of the Backfill with SHMP amendment. Overall, SHMP is shown to be a promising Ca-bentontie modifier for use in Backfill for slurry trench cutoff wall for effective containment of Pb-contaminated groundwater.
Dennis T. Bergado - One of the best experts on this subject based on the ideXlab platform.
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Embankment reinforced with limited life geotextiles on soft clay
Proceedings of the Institution of Civil Engineers - Ground Improvement, 2015Co-Authors: S. Artidteang, Dennis T. Bergado, S. Chaiyaput, T. TanchaisawatAbstract:This paper focuses on the behaviour of a full-scale test embankment with silty Sand Backfill on soft ground reinforced with kenaf limited life geotextiles (LLGs). Slide 5·0 software is used to analyse the stability of the embankment with kenaf LLGs and indicates a higher factor of safety than without kenaf LLGs. Surface settlements, subsurface settlements, excess pore water pressures and deformations of kenaf LLGs reinforcement are monitored and predicted. The predicted settlements agree well with measured values in the field but are overestimated by the Terzaghi one-dimensional consolidation method, as expected. There is close agreement between the measured and predicted settlements by Asaoka's method, as well as the predicted pore pressures using Skempton–Bjerrum predictions. Deformations are observed for LLG reinforcements which mobilised reinforcement tension up to 20 kN/m following the settlement pattern. After construction, the rates of settlement increase up to 250 days owing to the dissipation of ...
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Lightweight recycled geomaterials reinforced with geogrids
2010Co-Authors: P Voottipruex, Dennis T. Bergado, T. TanchaisawatAbstract:Scrap tyres are unwanted urban waste, the volume of which is increasing every year. One possible recycling method is for the shredded tyres, either alone or mixed with soil, to be used as a lightweight geomaterial. The present study aimed to examine (a) the interactions between geogrids and a tyre chips–Sand mixture, (b) the performance of a full-scale geogrid-reinforced test embankment and (c) a numerical simulation of this full-scale test embankment. Numerous experiments were performed in the laboratory to investigate the interactions between the geogrid and the tyre chips–Sand mixture. A full-scale, geogrid-reinforced embankment with lightweight tyre chips–Sand fill was then constructed on soft Bangkok clay and extensively instrumented to evaluate its performance. The unit weight of rubber tyre chip–Sand mixtures with ratio 30:70 per cent by weight was 13·6 kN/m3 compared with 18·0 kN/m3 for conventional Sand Backfill. The total settlement magnitude of 122 mm of the lightweight embankment was 67·5% les...
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2D and 3D simulation of geogrid-reinforced geocomposite material embankment on soft Bangkok clay
Geosynthetics International, 2009Co-Authors: T. Tanchaisawat, Dennis T. Bergado, Panich VoottipruexAbstract:ABSTRACT: A full-scale test embankment, 6.0 m high, was constructed on soft Bangkok clay using a rubber tire chip–Sand mixture as a geocomposite material reinforced with geogrid reinforcement with concrete block facing in the middle portion of the embankment. Silty Sand Backfill with rock-filled gabion facing were utilized at the sloping sides. The vertical and lateral deformations as well as excess pore pressures were monitored for 1 year. This study attempted to simulate the behavior of the full-scale test embankment by two-dimensional (2D) and three-dimensional (3D) numerical analyses. The 2D analysis was performed by PLAXIS software using undrained analysis in the construction stage and, thereafter, consolidation analysis was performed during the service stage. The 3D analysis was investigated by FLAC3D software using the same constitutive models and properties of foundation soils as published by previous researchers. Owing to the use of geocomposite material as embankment materials, the observed valu...
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The interaction mechanism and behavior of hexagonal wire mesh reinforced embankment with silty Sand Backfill on soft clay
Computers and Geotechnics, 2003Co-Authors: Dennis T. Bergado, Chairat Teerawattanasuk, Sompote Youwai, P VisudmedanukulAbstract:Abstract The pullout/direct shear mechanisms as well as the behavior of hexagonal wire mesh reinforced embankment with silty Sand Backfill had been investigated by numerical method. Finite element method under plane strain condition using SAGE CRISP software has been utilized in the numerical simulations. For the numerical simulation of full-scale reinforced wall, the reinforcement stiffness, Backfill soil properties, soil/reinforcement interaction, properties of soft clay foundation, and consolidation period were significantly considered in the analysis. The equivalent interaction coefficients of the interface element were used in the simulations for the pullout and direct shear modes. The results have been favorably compared with the previous simulation using PLAXIS FEM software. The numerical technique has reasonably captured the actual behavior of the reinforced embankment on soft foundation. Most of the interaction mode obtained from the simulation is governed by the direct shear mechanism.
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Analytical Models for Predicting the Pullout Capacity and Interaction between Hexagonal Wire Mesh and Silty Sand Backfill
2001Co-Authors: Dennis T. Bergado, Chairat TeerawattanasukAbstract:Large pullout tests were conducted on hexagonal wire mesh embedded in silty Sand locally known as Ayutthaya Sand to investigate the soil reinforcement interaction. PVC-coated of hexagonal wire mesh was tested with different applied normal pressures ranging from 35 to 105 kPa. The hexagonal wire mesh specimens with 80x100 mm cell sizes were pulled at a rate of 1 mm/min. In the conventional pullout test wherein the clamping system is outside the pullout box, the deformation and movement of hexagonal wire mesh known as necking phenomenon occurred simultaneously during the pullout process. In order to reduce this phenomenon, the large pullout test was modified to install the clamping system inside the pullout box hereinafter called ”in-soil pullout test”. The total pullout resistance of hexagonal wire mesh reinforcement consists of two components, namely: friction and bearing resistance. An elastic-perfectly plastic model was used to simulate the friction resistance and relative displacement relation of hexagonal wire mesh while a hyperbolic model was applied to simulate the passive bearing resistance of the individual bearing member. The bearing resistance is approximately 4 to 6 times greater than the friction resistance. The maximum pullout resistances increased with increasing specimen lengths as well as the applied normal pressures. The in-soil pullout resistances are about 50% greater than the corresponding results from previous conventional pullout tests. Several analytical models for predicting the pullout resistance of hexagonal wire mesh reinforcement have been proposed and modified in this paper. These proposed analytical models for predicting the pullout resistance and displacement relation agreed with the laboratory test results reasonable well.
Krishna R Reddy - One of the best experts on this subject based on the ideXlab platform.
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shmp amended ca bentonite Sand Backfill barrier for containment of lead contamination in groundwater
International Journal of Environmental Research and Public Health, 2020Co-Authors: Yuling Yang, Krishna R Reddy, Wenjie Zhang, Ridong FanAbstract:This study investigated the feasibility of using sodium hexametaphosphate (SHMP)- amended calcium (Ca) bentonite in Backfills for slurry trench cutoff walls for the containment of lead (Pb) contamination in groundwater. Backfills composed of 80 wt% Sand and 20 wt% either Ca-bentonite or SHMP-amended Ca-bentonite were tested for hydraulic conductivity and sorption properties by conducting laboratory flexible-wall hydraulic conductivity tests and batch isothermal sorption experiments, respectively. The results showed that the SHMP amendment causes a one order of magnitude decrease in hydraulic conductivity of the Backfill using tap water (1.9 to 3.0 × 10−10 m/s). Testing using 1000 mg/L Pb solution resulted insignificant variation in hydraulic conductivity of the amended Backfill. Moreover, SHMP-amendment induced favorable conditions for increased sorption capacity of the Backfill, with 1.5 times higher retardation factor relative to the unamended Backfill. The Pb transport modeling through an hypothetical 1-m-thick slurry wall composed of amended Backfill revealed 12 to 24 times of longer breakthrough time for Pb migration as compared to results obtained for the same thickness slurry wall with unamended Backfill, which is attributed to decrease in seepage velocity combined with increase in retardation factor of the Backfill with SHMP amendment. Overall, SHMP is shown to be a promising Ca-bentontie modifier for use in Backfill for slurry trench cutoff wall for effective containment of Pb-contaminated groundwater.
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SHMP-Amended Ca-Bentonite/Sand Backfill Barrier for Containment of Lead Contamination in Groundwater
International journal of environmental research and public health, 2020Co-Authors: Yuling Yang, Krishna R Reddy, Wenjie Zhang, Ridong FanAbstract:This study investigated the feasibility of using sodium hexametaphosphate (SHMP)- amended calcium (Ca) bentonite in Backfills for slurry trench cutoff walls for the containment of lead (Pb) contamination in groundwater. Backfills composed of 80 wt% Sand and 20 wt% either Ca-bentonite or SHMP-amended Ca-bentonite were tested for hydraulic conductivity and sorption properties by conducting laboratory flexible-wall hydraulic conductivity tests and batch isothermal sorption experiments, respectively. The results showed that the SHMP amendment causes a one order of magnitude decrease in hydraulic conductivity of the Backfill using tap water (1.9 to 3.0 × 10−10 m/s). Testing using 1000 mg/L Pb solution resulted insignificant variation in hydraulic conductivity of the amended Backfill. Moreover, SHMP-amendment induced favorable conditions for increased sorption capacity of the Backfill, with 1.5 times higher retardation factor relative to the unamended Backfill. The Pb transport modeling through an hypothetical 1-m-thick slurry wall composed of amended Backfill revealed 12 to 24 times of longer breakthrough time for Pb migration as compared to results obtained for the same thickness slurry wall with unamended Backfill, which is attributed to decrease in seepage velocity combined with increase in retardation factor of the Backfill with SHMP amendment. Overall, SHMP is shown to be a promising Ca-bentontie modifier for use in Backfill for slurry trench cutoff wall for effective containment of Pb-contaminated groundwater.
