J. N. Mandal | Indian Institute of Technology Bombay (original) (raw)
Papers by J. N. Mandal
International Journal of Geosynthetics and Ground Engineering, 2022
Stabilization of weak soils for road infrastructural applications is a challenging task. Such soi... more Stabilization of weak soils for road infrastructural applications is a challenging task. Such soils if properly stabilized with innovative technologies, could be adopted in sub-base courses by replacing conventional granular sub-bases for the construction of low-volume roads. In this research, stabilization of silty sand with nano zinc oxide and cement was carried out by adding 1%, 1.5%, and 2% of nano ZnO with 2%, 4% and 6% of cement, respectively. Experiments were organized to examine the effects on proctor compaction, CBR, UCS and Atterberg limit tests. Soaked CBR values of soil doped with 1.5% nano ZnO were substantially enhanced by 158.5%, 311.9%, and 365.3% when treated with 2%, 4% and 6% cement. UCS values were also observed to be drastically improved with the age of curing. Similarly, Atterberg limits on optimized proportion also disclosed a reduction in plasticity characteristics of the soil. Microstructural changes monitored with SEM analysis also supported the experimental results. TCLP test revealed the concentrations of heavy metals in the leachate within permissible limits for the optimized proportion. Strain analysis was carried out by IITPAVE based on four cases of the optimized mix. Soil stabilized with 1.5% nano ZnO and 6% cement was found to be optimal mix and suitable as sub-base material which could fulfill the criteria for chemically stabilized sub-base courses for low volume roads.
Procedia Engineering, 2017
During Capacity augmentation of existing National Highway (NH) Projects, grade separated structur... more During Capacity augmentation of existing National Highway (NH) Projects, grade separated structures in terms of Flyovers, Vehicular underpass (VUP), Pedestrian underpass (PUP), Cattle underpasses (CUP) are proposed at regular intervals. Accordingly, existing road levels at approaches of these structures are required to be raised making the existing pavement materials redundant. Existing pavement materials are also obtained due to milling of existing pavement surface before laying overlay for strengthening. The present study is to assess the suitability of using these redundant pavement materials also called Reclaimed Asphalt Pavement (RAP) as potential subbase / base course materials for flexible pavement. It was observed from literature survey of various past studies that California bearing ratio (CBR) of 100% RAP is not suitable for its use as base of flexible pavement as per Indian Standards (IRC). Accordingly, attempts were made to improve strength of RAP in terms of CBR by mixing it with crushed stone aggregates, stabilizing it with cement and combination of both. In the present study, laboratory CBR tests have been conducted on RAP, mixture of RAP and crushed stone aggregates and also on mixture of RAP and crushed stone aggregates stabilized with various percentages of cement. It was observed that though un soaked CBR values of RAP were not influenced much due to its mixing with crushed stone aggregates and/or stabilization with cement, soaked CBR values increased substantially due to both mixing with crushed stone aggregates and stabilizing with cement. The soaked CBR value of RAP increases from 20% to in excess of 100% when it is mixed with crushed stone aggregates in various proportions and stabilized with small percentages of cement and thereby making it suitable for using it as subbase/base of flexible pavement. Modified proctor compaction tests were conducted on both RAP and mixture of RAP and crushed stone aggregates to established optimum moisture content for the preparation of CBR moulds for testings.
Journal of Hazardous, Toxic, and Radioactive Waste, 2017
AbstractThis study narrates the use of postconsumer waste plastic water bottles for developing a ... more AbstractThis study narrates the use of postconsumer waste plastic water bottles for developing a new type of encasement to confine fly-ash columns fully penetrated in soft clay. Geocell-reinforced ...
Journal of Hazardous, Toxic, and Radioactive Waste, 2017
AbstractThis paper directs its aim to present a new approach to convert fly ash from becoming a h... more AbstractThis paper directs its aim to present a new approach to convert fly ash from becoming a hazardous waste for the environment into an artificial resource as effective construction material. T...
Journal of Hazardous, Toxic, and Radioactive Waste, 2014
AbstractIn India, pulverized coal is used at thermal power stations as a fuel to generate electri... more AbstractIn India, pulverized coal is used at thermal power stations as a fuel to generate electricity, thereby producing enormous quantities of fly ash. The amount of fly ash has been increased with the increasing demand of electric utilities. The utilization of fly ash and its disposal in an environmentally friendly manner is a foremost concern for developing countries like India. In this present study, with the aim of proper utilization of fly ash, a series of model experiments was conducted by using fly ash as a backfill material in a cellular-reinforced fly-ash wall subjected to strip loading. Two different types of locally available waste water bottles were used to make cellular reinforcements. The reinforcements were laid in two different patterns, mattress and strip. This paper studies and presents the effects of changes in length, spacing, coverage ratio, and dimensions of the cellular reinforcements on the horizontal displacement behavior of a full height facing panel and on the settlement of bac...
International Journal of Geotechnical Engineering, 2009
Abstract Pullout failure of reinforcement is one of the very important criteria in the ultimate l... more Abstract Pullout failure of reinforcement is one of the very important criteria in the ultimate limit sate analysis of internal stability of reinforced soil retaining wall. This is particularly of critical importance in upper layers of wall where the normal pressure on the reinforcement is low. Cellular reinforcement is found very effective and better performing for reinforced soil applications. However, pullout experimental study of such reinforcement has not been focused till date. Therefore, in the present paper, full scale laboratory pullout test set up has been designed, fabricated and developed to test the pullout resistance of cellular reinforcement. A series of pullout test was carried out with different heights of reinforcement, under low normal pressures of 25 kPa and 50 kPa. Deformation patterns of all reinforcement in pullout are studied. Finite element simulation is used to verify the experimental pullout response and found in good agreement with experimental load-displacement relationships. Suggested reduction factor ‘k’ is found decreasing with increase in height of reinforcement; yet, ultimate pullout resistance is found increasing with increase in the reinforcement height, to the height of 20 mm to 30 mm; after which, greater interference between the transverse members caused decrease in pullout resistance. Pullout interaction factor for cellular reinforcement is found increasing with increase in the reinforcement height.
Geotechnical Testing Journal, 2014
Thermal power stations in India produce an enormous quantity of fly ash as a by-product. Fly ash ... more Thermal power stations in India produce an enormous quantity of fly ash as a by-product. Fly ash utilization and disposal in an environmental friendly manner is a foremost concern in India. In the present study, an attempt has been made for proper utilization of fly ash as an alternative backfill material in geocell walls. This study also provides an approach for the use of waste plastic water bottles as geocells. The geocell diameter and height used in the model testing is 70 mm. Two types of structural geometry were considered in the study: gravity wall type and facing wall type. The lateral deformation of geocell wall and settlement of the backfill were studied under strip loading by varying facing angle of the wall, with and without reinforcement in the backfill. For both the type of walls, model testing results show that the maximum lateral deformation of geocell wall, backfill settlement, and failure surcharge pressures increased with decreasing facing angle of wall. For the reinforced case, the lateral deformation of the geocell wall was reduced considerably. When the reinforcement placed at top and total layers, the maximum lateral deformation of the geocell wall occurred at mid height of the wall. However, for bottom layers reinforced backfill, the maximum lateral deformation occurred at the top.
Geotechnical and Geological Engineering, 2007
... Mesh size (mm) 10·16 Tensile strength of geogrid (kN/m) 1.15 Elongation at maximum strength 6... more ... Mesh size (mm) 10·16 Tensile strength of geogrid (kN/m) 1.15 Elongation at maximum strength 6% Soilreinforcement interface friction angle (QS) 33° Fig. ... Strain along geogrids also Fig. 14 Strain distribution along geogrid layers for Model:B Case:I Location:I ...
Construction and Building Materials, 2022
Geosynthetics in Civil and Environmental Engineering
197 CENTRIFUGE MODELING ON FIBER REINFORCED FLY ASH SLOPE DK Bhardwaj1 and JN Mandal2 ... and Geo... more 197 CENTRIFUGE MODELING ON FIBER REINFORCED FLY ASH SLOPE DK Bhardwaj1 and JN Mandal2 ... and Geoenviroment Engrg. ASCE. 127 (7): 574584 Mandal JN, Kumar S, Meena CL (2005) Centrifuge modeling of reinforced soil slopes using tire chips. GSP 140. ...
Lecture Notes in Civil Engineering, 2021
Advancements in Unsaturated Soil Mechanics, 2019
India is the second most sugarcane producer in the world and generates 10 million tons of bagasse... more India is the second most sugarcane producer in the world and generates 10 million tons of bagasse ash every year. Bagasse ash is generally spread as fertilizer in the field. It is the most frequent method of disposing of bagasse ash. However, it contains heavy metals which may lead to adverse effect on the yielding of the crop. Hence, some scholars recommend not using bagasse ash as fertilizer. Previous studies indicated that bagasse ash has been significantly used as a fine aggregate in concrete. As a fine aggregate bagasse ash also has the potential to be an alternative filling material. However, a comprehensive characterization of bagasse ash as an alternative filling material is significantly lacking. The present study aims at the characterization of bagasse ash as an alternative filling material instead of natural material. A series of direct shear test and permeability test were conducted for this purpose. The effect of water content and dry density on the shear strength parameter and permeability were studied. The test results show that angle of internal friction and apparent cohesion increase up to optimum moisture content and decreased after wards. The permeability of test specimen decreased with an increase in dry density. As a result, bagasse ash is comparable with conventional fill material.
International Journal of Geotechnical Engineering, 2018
Soil reinforcement with bamboo is the oldest and the cheapest technique used to strengthen the ba... more Soil reinforcement with bamboo is the oldest and the cheapest technique used to strengthen the bases for rural roads and low budget buildings. The easy availability of bamboo at low cost and eco-friendly nature proves that it is better than costly geosynthetic materials. Bamboo is a natural reinforcement material, manufactured by bamboo strips, and has been accepted as a substitute to geogrid for reinforcement applications, due to its tensile strength properties. An effective use of bamboo depends upon the configuration of mattresses. The bamboo grid reinforcement can have either a square opening or a hexagonal opening. The results of small-scale load tests on sand reinforced with the bamboo grid of different aperture shapes are presented in this paper. The two different aperture shapes used in the bamboo grid are hexagonal (tridirectional) and square (bidirectional) form. The parameters studied in this experimental investigation included the effects of the location of the top reinforcement layer, size of reinforcement, number of reinforcement layers and aperture shape of the bamboo grid. The test results indicate that the hexagonal aperture bamboo grid provides better performance than the square aperture bamboo grid. The improvement factors in bearing pressure and percentage reduction in the settlement ratio were found 4.3% and 81%, respectively, with the use of tridirectional bamboo grid reinforcement, while these parameters were obtained 3.0% and 68% for the bidirectional bamboo grid reinforcement at the settlement ratio of 7.5%.
International Journal of Geomechanics, 2017
AbstractThis paper presents the results of large-scale numerical modeling of cellular mattress–re... more AbstractThis paper presents the results of large-scale numerical modeling of cellular mattress–reinforced fly ash beds overlying soft clay using a finite-element program. The cellular mattress was a honeycomb structure consisting of interconnected multiple circular cells. The influence of the height, diameter, and tensile stiffness of the cell and the width of the entire mattress on the pressure-settlement response of footing, surface deformation during footing settlement, and mobilization of hoop tension in the cell walls are illustrated. Results from the numerical analyses indicate an improvement in footing capacity of approximately1.4 times greater over fly ash bed by inclusion of a single geotextile separator representing jute geotextile in between the fly ash bed and underlying clay. The cellular mattress–fly ash composite bed produced an approximately sevenfold increment in the footing capacity compared with the unreinforced fly ash bed both in presence of the jute separator. The mattress-reinforced...
International Journal of Geomechanics, 2017
AbstractA numerical protocol was developed for the evaluation of the passive earth-pressure coeff... more AbstractA numerical protocol was developed for the evaluation of the passive earth-pressure coefficients (Kpq) for the case of an inclined rigid wall retaining an inclined cohesionless backfill loaded with a uniform surcharge. The shape of the proposed failure surface is assumed to be a complete log-spiral. The methodology developed herein uses Kotter’s equation, which enables the computation of soil reactive pressure distribution and the resultant soil reaction on the failure surface. Furthermore, all three limit-equilibrium conditions are effectively utilized to identify the unique failure surface for the given parameters, viz, soil frictional angle (ϕ), wall frictional angle (δ), wall inclination angle (λ), and sloping backfill angle (i). Design tables are also presented for several combinations of ϕ, δ, λ, and i. For validation, the Kpq values obtained are compared with those reported by several other researchers and are found to be in good agreement with most of the available theoretical solutions.
International Journal of Geomechanics, 2017
AbstractA numerical protocol was developed to compute the passive earth pressure coefficients, Kp... more AbstractA numerical protocol was developed to compute the passive earth pressure coefficients, Kpγ, for the case of an inclined rigid wall retaining an inclined cohesionless backfill. A complete log-spiral failure surface is assumed in this study. Kotter's equation is used in the analysis to obtain the resultant soil reaction on the failure surface. In addition, a limit-equilibrium approach is used to identify the unique failure surface, which fulfils all three equilibrium conditions, viz., ∑H = 0, ∑V = 0, and ∑M = 0, with the passive thrust located at the lower one-third height of the retaining wall. The analysis is further extended to evaluate the bearing capacity factor, Nγ, for the case of a centrally loaded rigid rough strip footing resting on a cohesionless soil medium. For this purpose, particular failure mechanisms are considered. The computed Nγ values are found to be in good agreement with most of the available theoretical solutions.
International Journal of Geotechnical Engineering, 2016
Fly ash, waste by-product from coal industries, is being used extensively in construction of high... more Fly ash, waste by-product from coal industries, is being used extensively in construction of highway and railway embankments. This paper describes the effectiveness of steel grid reinforcement in the form of planar mattress along with jute geotextile at facia throughout the slope and with fly ash as backfill material. The models were subjected to loading in the form of uniform and strip loading by means of rigid steel plates as footings. Series of laboratory model tests were carried out on homogeneous unreinforced and reinforced fly ash slopes with slope angle 60° on rigid base to check the efficacy of reinforcement in improving the load carrying capacity and stability of slope. For fly ash slope on rigid base, length of the reinforcement was varied from 0.7H to 0.2H (H = Height of the slope). The steel reinforcement having grid thickness of 1.2 mm with square openings of 15 mm was laid along the width of the slope in continuous form as well as with coverage ratios (Cr) of 0.5 and 0.6. All the tests were conducted by applying both uniformly distributed load (UDL) and strip loading until failure. Based on the experimental results, for all types of reinforcement cases, slope with continuous grid of length 0.7H supports maximum for strip loading before failure as compared to UDL. The variation in length of the reinforcement showed significant effect on the settlement of the backfill.
International Journal of Geosynthetics and Ground Engineering, 2022
Stabilization of weak soils for road infrastructural applications is a challenging task. Such soi... more Stabilization of weak soils for road infrastructural applications is a challenging task. Such soils if properly stabilized with innovative technologies, could be adopted in sub-base courses by replacing conventional granular sub-bases for the construction of low-volume roads. In this research, stabilization of silty sand with nano zinc oxide and cement was carried out by adding 1%, 1.5%, and 2% of nano ZnO with 2%, 4% and 6% of cement, respectively. Experiments were organized to examine the effects on proctor compaction, CBR, UCS and Atterberg limit tests. Soaked CBR values of soil doped with 1.5% nano ZnO were substantially enhanced by 158.5%, 311.9%, and 365.3% when treated with 2%, 4% and 6% cement. UCS values were also observed to be drastically improved with the age of curing. Similarly, Atterberg limits on optimized proportion also disclosed a reduction in plasticity characteristics of the soil. Microstructural changes monitored with SEM analysis also supported the experimental results. TCLP test revealed the concentrations of heavy metals in the leachate within permissible limits for the optimized proportion. Strain analysis was carried out by IITPAVE based on four cases of the optimized mix. Soil stabilized with 1.5% nano ZnO and 6% cement was found to be optimal mix and suitable as sub-base material which could fulfill the criteria for chemically stabilized sub-base courses for low volume roads.
Procedia Engineering, 2017
During Capacity augmentation of existing National Highway (NH) Projects, grade separated structur... more During Capacity augmentation of existing National Highway (NH) Projects, grade separated structures in terms of Flyovers, Vehicular underpass (VUP), Pedestrian underpass (PUP), Cattle underpasses (CUP) are proposed at regular intervals. Accordingly, existing road levels at approaches of these structures are required to be raised making the existing pavement materials redundant. Existing pavement materials are also obtained due to milling of existing pavement surface before laying overlay for strengthening. The present study is to assess the suitability of using these redundant pavement materials also called Reclaimed Asphalt Pavement (RAP) as potential subbase / base course materials for flexible pavement. It was observed from literature survey of various past studies that California bearing ratio (CBR) of 100% RAP is not suitable for its use as base of flexible pavement as per Indian Standards (IRC). Accordingly, attempts were made to improve strength of RAP in terms of CBR by mixing it with crushed stone aggregates, stabilizing it with cement and combination of both. In the present study, laboratory CBR tests have been conducted on RAP, mixture of RAP and crushed stone aggregates and also on mixture of RAP and crushed stone aggregates stabilized with various percentages of cement. It was observed that though un soaked CBR values of RAP were not influenced much due to its mixing with crushed stone aggregates and/or stabilization with cement, soaked CBR values increased substantially due to both mixing with crushed stone aggregates and stabilizing with cement. The soaked CBR value of RAP increases from 20% to in excess of 100% when it is mixed with crushed stone aggregates in various proportions and stabilized with small percentages of cement and thereby making it suitable for using it as subbase/base of flexible pavement. Modified proctor compaction tests were conducted on both RAP and mixture of RAP and crushed stone aggregates to established optimum moisture content for the preparation of CBR moulds for testings.
Journal of Hazardous, Toxic, and Radioactive Waste, 2017
AbstractThis study narrates the use of postconsumer waste plastic water bottles for developing a ... more AbstractThis study narrates the use of postconsumer waste plastic water bottles for developing a new type of encasement to confine fly-ash columns fully penetrated in soft clay. Geocell-reinforced ...
Journal of Hazardous, Toxic, and Radioactive Waste, 2017
AbstractThis paper directs its aim to present a new approach to convert fly ash from becoming a h... more AbstractThis paper directs its aim to present a new approach to convert fly ash from becoming a hazardous waste for the environment into an artificial resource as effective construction material. T...
Journal of Hazardous, Toxic, and Radioactive Waste, 2014
AbstractIn India, pulverized coal is used at thermal power stations as a fuel to generate electri... more AbstractIn India, pulverized coal is used at thermal power stations as a fuel to generate electricity, thereby producing enormous quantities of fly ash. The amount of fly ash has been increased with the increasing demand of electric utilities. The utilization of fly ash and its disposal in an environmentally friendly manner is a foremost concern for developing countries like India. In this present study, with the aim of proper utilization of fly ash, a series of model experiments was conducted by using fly ash as a backfill material in a cellular-reinforced fly-ash wall subjected to strip loading. Two different types of locally available waste water bottles were used to make cellular reinforcements. The reinforcements were laid in two different patterns, mattress and strip. This paper studies and presents the effects of changes in length, spacing, coverage ratio, and dimensions of the cellular reinforcements on the horizontal displacement behavior of a full height facing panel and on the settlement of bac...
International Journal of Geotechnical Engineering, 2009
Abstract Pullout failure of reinforcement is one of the very important criteria in the ultimate l... more Abstract Pullout failure of reinforcement is one of the very important criteria in the ultimate limit sate analysis of internal stability of reinforced soil retaining wall. This is particularly of critical importance in upper layers of wall where the normal pressure on the reinforcement is low. Cellular reinforcement is found very effective and better performing for reinforced soil applications. However, pullout experimental study of such reinforcement has not been focused till date. Therefore, in the present paper, full scale laboratory pullout test set up has been designed, fabricated and developed to test the pullout resistance of cellular reinforcement. A series of pullout test was carried out with different heights of reinforcement, under low normal pressures of 25 kPa and 50 kPa. Deformation patterns of all reinforcement in pullout are studied. Finite element simulation is used to verify the experimental pullout response and found in good agreement with experimental load-displacement relationships. Suggested reduction factor ‘k’ is found decreasing with increase in height of reinforcement; yet, ultimate pullout resistance is found increasing with increase in the reinforcement height, to the height of 20 mm to 30 mm; after which, greater interference between the transverse members caused decrease in pullout resistance. Pullout interaction factor for cellular reinforcement is found increasing with increase in the reinforcement height.
Geotechnical Testing Journal, 2014
Thermal power stations in India produce an enormous quantity of fly ash as a by-product. Fly ash ... more Thermal power stations in India produce an enormous quantity of fly ash as a by-product. Fly ash utilization and disposal in an environmental friendly manner is a foremost concern in India. In the present study, an attempt has been made for proper utilization of fly ash as an alternative backfill material in geocell walls. This study also provides an approach for the use of waste plastic water bottles as geocells. The geocell diameter and height used in the model testing is 70 mm. Two types of structural geometry were considered in the study: gravity wall type and facing wall type. The lateral deformation of geocell wall and settlement of the backfill were studied under strip loading by varying facing angle of the wall, with and without reinforcement in the backfill. For both the type of walls, model testing results show that the maximum lateral deformation of geocell wall, backfill settlement, and failure surcharge pressures increased with decreasing facing angle of wall. For the reinforced case, the lateral deformation of the geocell wall was reduced considerably. When the reinforcement placed at top and total layers, the maximum lateral deformation of the geocell wall occurred at mid height of the wall. However, for bottom layers reinforced backfill, the maximum lateral deformation occurred at the top.
Geotechnical and Geological Engineering, 2007
... Mesh size (mm) 10·16 Tensile strength of geogrid (kN/m) 1.15 Elongation at maximum strength 6... more ... Mesh size (mm) 10·16 Tensile strength of geogrid (kN/m) 1.15 Elongation at maximum strength 6% Soilreinforcement interface friction angle (QS) 33° Fig. ... Strain along geogrids also Fig. 14 Strain distribution along geogrid layers for Model:B Case:I Location:I ...
Construction and Building Materials, 2022
Geosynthetics in Civil and Environmental Engineering
197 CENTRIFUGE MODELING ON FIBER REINFORCED FLY ASH SLOPE DK Bhardwaj1 and JN Mandal2 ... and Geo... more 197 CENTRIFUGE MODELING ON FIBER REINFORCED FLY ASH SLOPE DK Bhardwaj1 and JN Mandal2 ... and Geoenviroment Engrg. ASCE. 127 (7): 574584 Mandal JN, Kumar S, Meena CL (2005) Centrifuge modeling of reinforced soil slopes using tire chips. GSP 140. ...
Lecture Notes in Civil Engineering, 2021
Advancements in Unsaturated Soil Mechanics, 2019
India is the second most sugarcane producer in the world and generates 10 million tons of bagasse... more India is the second most sugarcane producer in the world and generates 10 million tons of bagasse ash every year. Bagasse ash is generally spread as fertilizer in the field. It is the most frequent method of disposing of bagasse ash. However, it contains heavy metals which may lead to adverse effect on the yielding of the crop. Hence, some scholars recommend not using bagasse ash as fertilizer. Previous studies indicated that bagasse ash has been significantly used as a fine aggregate in concrete. As a fine aggregate bagasse ash also has the potential to be an alternative filling material. However, a comprehensive characterization of bagasse ash as an alternative filling material is significantly lacking. The present study aims at the characterization of bagasse ash as an alternative filling material instead of natural material. A series of direct shear test and permeability test were conducted for this purpose. The effect of water content and dry density on the shear strength parameter and permeability were studied. The test results show that angle of internal friction and apparent cohesion increase up to optimum moisture content and decreased after wards. The permeability of test specimen decreased with an increase in dry density. As a result, bagasse ash is comparable with conventional fill material.
International Journal of Geotechnical Engineering, 2018
Soil reinforcement with bamboo is the oldest and the cheapest technique used to strengthen the ba... more Soil reinforcement with bamboo is the oldest and the cheapest technique used to strengthen the bases for rural roads and low budget buildings. The easy availability of bamboo at low cost and eco-friendly nature proves that it is better than costly geosynthetic materials. Bamboo is a natural reinforcement material, manufactured by bamboo strips, and has been accepted as a substitute to geogrid for reinforcement applications, due to its tensile strength properties. An effective use of bamboo depends upon the configuration of mattresses. The bamboo grid reinforcement can have either a square opening or a hexagonal opening. The results of small-scale load tests on sand reinforced with the bamboo grid of different aperture shapes are presented in this paper. The two different aperture shapes used in the bamboo grid are hexagonal (tridirectional) and square (bidirectional) form. The parameters studied in this experimental investigation included the effects of the location of the top reinforcement layer, size of reinforcement, number of reinforcement layers and aperture shape of the bamboo grid. The test results indicate that the hexagonal aperture bamboo grid provides better performance than the square aperture bamboo grid. The improvement factors in bearing pressure and percentage reduction in the settlement ratio were found 4.3% and 81%, respectively, with the use of tridirectional bamboo grid reinforcement, while these parameters were obtained 3.0% and 68% for the bidirectional bamboo grid reinforcement at the settlement ratio of 7.5%.
International Journal of Geomechanics, 2017
AbstractThis paper presents the results of large-scale numerical modeling of cellular mattress–re... more AbstractThis paper presents the results of large-scale numerical modeling of cellular mattress–reinforced fly ash beds overlying soft clay using a finite-element program. The cellular mattress was a honeycomb structure consisting of interconnected multiple circular cells. The influence of the height, diameter, and tensile stiffness of the cell and the width of the entire mattress on the pressure-settlement response of footing, surface deformation during footing settlement, and mobilization of hoop tension in the cell walls are illustrated. Results from the numerical analyses indicate an improvement in footing capacity of approximately1.4 times greater over fly ash bed by inclusion of a single geotextile separator representing jute geotextile in between the fly ash bed and underlying clay. The cellular mattress–fly ash composite bed produced an approximately sevenfold increment in the footing capacity compared with the unreinforced fly ash bed both in presence of the jute separator. The mattress-reinforced...
International Journal of Geomechanics, 2017
AbstractA numerical protocol was developed for the evaluation of the passive earth-pressure coeff... more AbstractA numerical protocol was developed for the evaluation of the passive earth-pressure coefficients (Kpq) for the case of an inclined rigid wall retaining an inclined cohesionless backfill loaded with a uniform surcharge. The shape of the proposed failure surface is assumed to be a complete log-spiral. The methodology developed herein uses Kotter’s equation, which enables the computation of soil reactive pressure distribution and the resultant soil reaction on the failure surface. Furthermore, all three limit-equilibrium conditions are effectively utilized to identify the unique failure surface for the given parameters, viz, soil frictional angle (ϕ), wall frictional angle (δ), wall inclination angle (λ), and sloping backfill angle (i). Design tables are also presented for several combinations of ϕ, δ, λ, and i. For validation, the Kpq values obtained are compared with those reported by several other researchers and are found to be in good agreement with most of the available theoretical solutions.
International Journal of Geomechanics, 2017
AbstractA numerical protocol was developed to compute the passive earth pressure coefficients, Kp... more AbstractA numerical protocol was developed to compute the passive earth pressure coefficients, Kpγ, for the case of an inclined rigid wall retaining an inclined cohesionless backfill. A complete log-spiral failure surface is assumed in this study. Kotter's equation is used in the analysis to obtain the resultant soil reaction on the failure surface. In addition, a limit-equilibrium approach is used to identify the unique failure surface, which fulfils all three equilibrium conditions, viz., ∑H = 0, ∑V = 0, and ∑M = 0, with the passive thrust located at the lower one-third height of the retaining wall. The analysis is further extended to evaluate the bearing capacity factor, Nγ, for the case of a centrally loaded rigid rough strip footing resting on a cohesionless soil medium. For this purpose, particular failure mechanisms are considered. The computed Nγ values are found to be in good agreement with most of the available theoretical solutions.
International Journal of Geotechnical Engineering, 2016
Fly ash, waste by-product from coal industries, is being used extensively in construction of high... more Fly ash, waste by-product from coal industries, is being used extensively in construction of highway and railway embankments. This paper describes the effectiveness of steel grid reinforcement in the form of planar mattress along with jute geotextile at facia throughout the slope and with fly ash as backfill material. The models were subjected to loading in the form of uniform and strip loading by means of rigid steel plates as footings. Series of laboratory model tests were carried out on homogeneous unreinforced and reinforced fly ash slopes with slope angle 60° on rigid base to check the efficacy of reinforcement in improving the load carrying capacity and stability of slope. For fly ash slope on rigid base, length of the reinforcement was varied from 0.7H to 0.2H (H = Height of the slope). The steel reinforcement having grid thickness of 1.2 mm with square openings of 15 mm was laid along the width of the slope in continuous form as well as with coverage ratios (Cr) of 0.5 and 0.6. All the tests were conducted by applying both uniformly distributed load (UDL) and strip loading until failure. Based on the experimental results, for all types of reinforcement cases, slope with continuous grid of length 0.7H supports maximum for strip loading before failure as compared to UDL. The variation in length of the reinforcement showed significant effect on the settlement of the backfill.