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Papers by Ujwalkumar Patil

Research paper thumbnail of Bioengineering Solution to Prevent Rainfall-Induced Slope Failures in Tropical Soil

Land, 2021

This paper presents test results of comprehensive laboratory and field-testing program efforts fo... more This paper presents test results of comprehensive laboratory and field-testing program efforts for the development of bioengineering solutions such as growing vegetation for protection of slopes from erosion and landslides in a tropical environmental setting. Saturated shear strength of soil was determined using direct shear tests and unsaturated soil properties, such as soil water retention curve (SWRC), were obtained using a computer-controlled hydraulic property analyzer (HYROP) system as well as a WP4C instrument. Climate data were obtained via field instrumentation and appropriate vegetation data were assumed to perform a finite element method-based transient seepage analysis and coupled slope stability analysis to test the potential of tropical hillslope to fail with and without vegetation over a period of one month. Results show that the factor of safety (FOS) for test slope considering case (a) the rainfall and bare ground, case (b) no rainfall with vegetation, and case (c) ...

Research paper thumbnail of Bounding Surface Modeling of Compacted Silty Sand Exhibiting Suction Dependent Post-peak Strain Softening

International audienceThis article focuses on modeling the strain hardening-softening response of... more International audienceThis article focuses on modeling the strain hardening-softening response of statically compacted silty sand as observed from a comprehensive series of suction-controlled, consolidated-drained triaxial tests accomplished in a fully-automated, double-walled triaxial test system via the axis-translation technique. The constitutive model used in this work is based on the theory of Bounding Surface (BS) plasticity, and is formulated within a critical state framework. The essential BS model parameters are calibrated using the full set of triaxial test results and then used for predictions of compacted silty sand response at matric suction states varying from 50 to 750 kPa. Complementary simulations using the Barcelona Basic Model (BBM) have also been included, alongside BS model predictions, in order to get further enlightening insights into some of the main limitations and challenges facing both frameworks within the context of the experimental evidence resulting fr...

Research paper thumbnail of Influence of vegetation in improving the stability of a hill slope in a tropical climate setting

Environmental Geotechnics

This paper aims at investigating and highlighting the hydrological benefit of vegetation via root... more This paper aims at investigating and highlighting the hydrological benefit of vegetation via root water uptake (RWU) in preventing or at the least delaying the rainfall-induced slope failures in Island of Guam. In particular, the results from field instrumentation and monitoring via moisture and suction sensors, laboratory and field testing for geotechnical and hydrological soil properties, and rainfall-induced numerical simulations of transient seepage coupled with slope stability analysis are presented. Two case studies, one with a 45° and another with a 60° slope were studied for three different case scenarios. Only one set of vegetation and root reinforcement data was idealized, and the results confirm that matric suction induced within shallow depth due to RWU helps in providing the buffer, which prevents slope failure during smaller precipitation events. However, this stabilization effect ceases after saturation during long duration precipitation. On the other hand, compliment...

Research paper thumbnail of Swell Mitigation with Granulated Tire Rubber

Journal of Materials in Civil Engineering, 2011

ABSTRACT Experiments were conducted to investigate the odometric swell behavior of expansive soil... more ABSTRACT Experiments were conducted to investigate the odometric swell behavior of expansive soil specimens mixed independently with two different granular additives: silica sand and granulated tire rubber (GTR). All specimens were prepared with the same global water content. However, specimens that contained sand swelled less than did analogous specimens that contained GTR, regardless of the surcharge stress imposed before inundation. Phase relationship analyses based on "oversize correction" equations derived for mixtures with three solid phases indicate that the specimens possessed clay portions with different dry density and initial water content. Such differences are attributed mainly to the role of additive grain stiffness during specimen preparation. Results from complementary discrete element method simulations indicate that the stiffness of the additive grains may also play a role in mitigating the swell via contact force alterations upon swell. DOI: 10.1061/(ASCE)MT.1943-5533.0000229. (C) 2011 American Society of Civil Engineers.

Research paper thumbnail of Modeling critical-state shear strength behavior of compacted silty sand via suction-controlled triaxial testing

Engineering Geology

Abstract Most of the recently postulated unsaturated shear strength models have been calibrated o... more Abstract Most of the recently postulated unsaturated shear strength models have been calibrated only for a short variety of soils. In addition, these models are yet to be extended and calibrated over a wider range of matric and total suction states. The present work focuses on further refinements of previously proposed shear strength equations in light of newly obtained experimental evidence of shear strength behavior of compacted silty sand at a critical state from suction-controlled triaxial tests conducted between 0.05 MPa to 300 MPa suction range. A refined and rather simple equation comprising two independent functions, is introduced and validated, including a thorough parametric investigation, to predict the unsaturated shear strength of compacted silty sand at a critical state for a wide range of matric and total suction states. The experimental program included a total of 21 consolidated drained (CD) triaxial tests conducted on statically-compacted specimens of silty sand under strain- and suction-controlled conditions. Experimental results show that the angle of internal friction (ϕ′) remained virtually constant over the entire range of induced suction states; however, the shear strength increased while the angle of internal friction with respect to suction (ϕb) decreased with increasing suction, with both varying non-linearly. Finally, a gradual increase in brittleness of the test soil at peak-failure condition, as well as an increasingly marked strain-softening post-failure, was observed with increasing suction.

Research paper thumbnail of Characterization of Compacted Silty Sand Using a Double-Walled Triaxial Cell With Fully Automated Relative-Humidity Control

Geotechnical Testing Journal, 2016

Research paper thumbnail of Resilient Modulus of Liquid Chemical-Treated Expansive Soils

Diluted acids are used as chemical stabilizers in Texas to treat expansive soils for residential ... more Diluted acids are used as chemical stabilizers in Texas to treat expansive soils for residential projects via deep injection. Due to the proprietary nature of the chemical stabilizers, there are very limited studies on the resilient modulus (MR) of chemically-treated expansive soils. This paper evaluates the effect of a liquid chemical stabilizer on the treatment of expansive soils collected from Texas and Colorado. The chemical solution, called ionic soil stabilizer (ISS) which contain sulfuric acid, phosphoric acid, citric acid, and water was used as an additive and tests were carried out on untreated and treated bulk soil samples in accordance with AASHTO T-307. The treated soil specimens were prepared by hand mixing the dry soils with the chemical stabilizer at three application ratios and two curing periods (7 and 28 days). The experiment results show that the value of resilient modulus increases with the increase of chemical application ratio. The resilient modulus of the trea...

Research paper thumbnail of Evaluation of Liquefaction Resistance in Silty Sand via Suction Controlled Cyclic Triaxial Tests

Research paper thumbnail of A Simplified Approach to Determine the Response of Unsaturated Soils Using Multistage Triaxial Test

Research paper thumbnail of Behavior of unsaturated cohesive-frictional soils over a whole range of suction/thermo-controlled stress paths and modes of deformation

Soils and Rocks

The present work documents some of the most recent experimental evidence of the thermohydro-mecha... more The present work documents some of the most recent experimental evidence of the thermohydro-mechanical behavior of compacted soils over a whole range of suction- and/or thermo-controlled stress paths and modes of deformation, including data from a series of triaxial, true triaxial, plane strain, ring shear, and resonant column tests conducted on different types of cohesive-frictional soils in the low-to-medium matric suction range under either room temperature or thermally controlled conditions. The work has been accomplished at the Advanced Geomechanics Laboratory of the University of Texas at Arlington, focusing primarily on the following essential features of unsaturated soil behavior: (1) Loading-collapse and apparent tensile strength loci assessed from suction-controlled triaxial and true triaxial testing on clayey sand, (2) Critical state lines from suction-controlled plane strain testing on silty soil, (3) Peak and residual failure envelopes from suction-controlled ring shear...

Research paper thumbnail of Assessment of Pavement Geometric Characteristics Using UAV-CRP Data

Research paper thumbnail of Response Of Unsaturated Silty Sand Over A Wider Range Of Suction States Using A Novel Double-walled Triaxial Testing System

RESPONSE OF UNSATURATED SILTY SAND OVER A WIDER RANGE OF SUCTION STATES USING A NOVEL DOUBLE-WALL... more RESPONSE OF UNSATURATED SILTY SAND OVER A WIDER RANGE OF SUCTION STATES USING A NOVEL DOUBLE-WALLED TRIAXIAL TESTING SYSTEM Ujwalkumar D. Patil, PhD The University of Texas at Arlington, 2014 Supervising Professor: Anand J. Puppala Co-Supervising Professor: Laureano R. Hoyos In recent decades, the state-of-the-art of our understanding of unsaturated soil performance has been considerably enhanced by the incorporation of novel and advanced features into the conventional testing devices such as direct shear device, ring shear device, triaxial device and true triaxial device. The novel suction-controlled triaxial system used in this research is fully automated and has enhanced features such as volume change device and double-walled cell to monitor the volume change accurately during all the stages of the unsaturated triaxial test. Despite their sophistication, such devices can help in testing mechanical behavior of unsaturated soils only up to the matric suction (s) value of 1500 kPa (...

Research paper thumbnail of Three-Dimensional Stability Analysis of Rock Slope Using Aerial Photogrammetry Data

Research paper thumbnail of Bioengineering Solution to Prevent Rainfall-Induced Slope Failures in Tropical Soil

Land, 2021

This paper presents test results of comprehensive laboratory and field-testing program efforts fo... more This paper presents test results of comprehensive laboratory and field-testing program efforts for the development of bioengineering solutions such as growing vegetation for protection of slopes from erosion and landslides in a tropical environmental setting. Saturated shear strength of soil was determined using direct shear tests and unsaturated soil properties, such as soil water retention curve (SWRC), were obtained using a computer-controlled hydraulic property analyzer (HYROP) system as well as a WP4C instrument. Climate data were obtained via field instrumentation and appropriate vegetation data were assumed to perform a finite element method-based transient seepage analysis and coupled slope stability analysis to test the potential of tropical hillslope to fail with and without vegetation over a period of one month. Results show that the factor of safety (FOS) for test slope considering case (a) the rainfall and bare ground, case (b) no rainfall with vegetation, and case (c) ...

Research paper thumbnail of Evaluation of Rock Slope Stability Using 3-Dimensional Data Analysis

Research paper thumbnail of Methodology for Resloping of Rock Slope Using 3D Models from UAV-CRP Technology

AbstractAssessing the stability of rock slopes is essential to ensuring the typical performance o... more AbstractAssessing the stability of rock slopes is essential to ensuring the typical performance of adjacent transportation infrastructures but simulating the existing field topography and boundary ...

Research paper thumbnail of Suction Stress Characteristic Curves of Cohesive-Frictional Soils from Multiple Suction-Controlled Testing Methods

International Journal of Geomechanics, 2020

In most geotechnical construction works, compacted soils of cohesive-frictional nature are expect... more In most geotechnical construction works, compacted soils of cohesive-frictional nature are expected to remain mostly under partially saturated conditions and hence experience continuous ch...

Research paper thumbnail of Effect of Rainfall Infiltration on Stability of a Tropical Slope from Western Pacific

Research paper thumbnail of Strength, Stiffness and Radial Anisotropy of Compacted Silty Sand Under Suction-Controlled Axisymmetric Shearing

Geotechnical and Geological Engineering

A thorough analysis of strength, stiffness, and stress-induced anisotropy of statically compacted... more A thorough analysis of strength, stiffness, and stress-induced anisotropy of statically compacted silty sand is presented based on results from a comprehensive suction-controlled (drained) triaxial test program. Induced soil suction values, via either axis-translation or relative humidity techniques, ranged between 0.05 to 300 MPa, with net confining pressures varying from 100 to 300 kPa. A relatively simple model/equation for peak friction angle (ϕpeak), over the entire test suction and net confinement range, is presented. As expected, peak strength response to suction-controlled monotonic shearing is influenced by the level of suction and net confining pressure, as well as the amount of dilatancy experienced by the silty sand. The nonlinear nature of the variation of deviator stress at peak and critical state conditions, with degree of saturation, was fitted reasonably well via fourth order and second order polynomial equations, respectively. A thorough analysis and modeling of stress-dilatancy behavior is presented in a companion paper. Finally, the inherent-anisotropy observed in the original soil fabric, as well as the stress induced-anisotropy observed in the sheared samples, are discussed based on results from suction-controlled isotropic consolidation and axisymmetric shearing, respectively; including the effect of suction on the rate of degradation of stiffness (moduli) of compacted silty sand under monotonic shearing.

Research paper thumbnail of Identifying hazardous obstructions within an intersection using unmanned aerial data analysis

International Journal of Transportation Science and Technology

Research paper thumbnail of Bioengineering Solution to Prevent Rainfall-Induced Slope Failures in Tropical Soil

Land, 2021

This paper presents test results of comprehensive laboratory and field-testing program efforts fo... more This paper presents test results of comprehensive laboratory and field-testing program efforts for the development of bioengineering solutions such as growing vegetation for protection of slopes from erosion and landslides in a tropical environmental setting. Saturated shear strength of soil was determined using direct shear tests and unsaturated soil properties, such as soil water retention curve (SWRC), were obtained using a computer-controlled hydraulic property analyzer (HYROP) system as well as a WP4C instrument. Climate data were obtained via field instrumentation and appropriate vegetation data were assumed to perform a finite element method-based transient seepage analysis and coupled slope stability analysis to test the potential of tropical hillslope to fail with and without vegetation over a period of one month. Results show that the factor of safety (FOS) for test slope considering case (a) the rainfall and bare ground, case (b) no rainfall with vegetation, and case (c) ...

Research paper thumbnail of Bounding Surface Modeling of Compacted Silty Sand Exhibiting Suction Dependent Post-peak Strain Softening

International audienceThis article focuses on modeling the strain hardening-softening response of... more International audienceThis article focuses on modeling the strain hardening-softening response of statically compacted silty sand as observed from a comprehensive series of suction-controlled, consolidated-drained triaxial tests accomplished in a fully-automated, double-walled triaxial test system via the axis-translation technique. The constitutive model used in this work is based on the theory of Bounding Surface (BS) plasticity, and is formulated within a critical state framework. The essential BS model parameters are calibrated using the full set of triaxial test results and then used for predictions of compacted silty sand response at matric suction states varying from 50 to 750 kPa. Complementary simulations using the Barcelona Basic Model (BBM) have also been included, alongside BS model predictions, in order to get further enlightening insights into some of the main limitations and challenges facing both frameworks within the context of the experimental evidence resulting fr...

Research paper thumbnail of Influence of vegetation in improving the stability of a hill slope in a tropical climate setting

Environmental Geotechnics

This paper aims at investigating and highlighting the hydrological benefit of vegetation via root... more This paper aims at investigating and highlighting the hydrological benefit of vegetation via root water uptake (RWU) in preventing or at the least delaying the rainfall-induced slope failures in Island of Guam. In particular, the results from field instrumentation and monitoring via moisture and suction sensors, laboratory and field testing for geotechnical and hydrological soil properties, and rainfall-induced numerical simulations of transient seepage coupled with slope stability analysis are presented. Two case studies, one with a 45° and another with a 60° slope were studied for three different case scenarios. Only one set of vegetation and root reinforcement data was idealized, and the results confirm that matric suction induced within shallow depth due to RWU helps in providing the buffer, which prevents slope failure during smaller precipitation events. However, this stabilization effect ceases after saturation during long duration precipitation. On the other hand, compliment...

Research paper thumbnail of Swell Mitigation with Granulated Tire Rubber

Journal of Materials in Civil Engineering, 2011

ABSTRACT Experiments were conducted to investigate the odometric swell behavior of expansive soil... more ABSTRACT Experiments were conducted to investigate the odometric swell behavior of expansive soil specimens mixed independently with two different granular additives: silica sand and granulated tire rubber (GTR). All specimens were prepared with the same global water content. However, specimens that contained sand swelled less than did analogous specimens that contained GTR, regardless of the surcharge stress imposed before inundation. Phase relationship analyses based on "oversize correction" equations derived for mixtures with three solid phases indicate that the specimens possessed clay portions with different dry density and initial water content. Such differences are attributed mainly to the role of additive grain stiffness during specimen preparation. Results from complementary discrete element method simulations indicate that the stiffness of the additive grains may also play a role in mitigating the swell via contact force alterations upon swell. DOI: 10.1061/(ASCE)MT.1943-5533.0000229. (C) 2011 American Society of Civil Engineers.

Research paper thumbnail of Modeling critical-state shear strength behavior of compacted silty sand via suction-controlled triaxial testing

Engineering Geology

Abstract Most of the recently postulated unsaturated shear strength models have been calibrated o... more Abstract Most of the recently postulated unsaturated shear strength models have been calibrated only for a short variety of soils. In addition, these models are yet to be extended and calibrated over a wider range of matric and total suction states. The present work focuses on further refinements of previously proposed shear strength equations in light of newly obtained experimental evidence of shear strength behavior of compacted silty sand at a critical state from suction-controlled triaxial tests conducted between 0.05 MPa to 300 MPa suction range. A refined and rather simple equation comprising two independent functions, is introduced and validated, including a thorough parametric investigation, to predict the unsaturated shear strength of compacted silty sand at a critical state for a wide range of matric and total suction states. The experimental program included a total of 21 consolidated drained (CD) triaxial tests conducted on statically-compacted specimens of silty sand under strain- and suction-controlled conditions. Experimental results show that the angle of internal friction (ϕ′) remained virtually constant over the entire range of induced suction states; however, the shear strength increased while the angle of internal friction with respect to suction (ϕb) decreased with increasing suction, with both varying non-linearly. Finally, a gradual increase in brittleness of the test soil at peak-failure condition, as well as an increasingly marked strain-softening post-failure, was observed with increasing suction.

Research paper thumbnail of Characterization of Compacted Silty Sand Using a Double-Walled Triaxial Cell With Fully Automated Relative-Humidity Control

Geotechnical Testing Journal, 2016

Research paper thumbnail of Resilient Modulus of Liquid Chemical-Treated Expansive Soils

Diluted acids are used as chemical stabilizers in Texas to treat expansive soils for residential ... more Diluted acids are used as chemical stabilizers in Texas to treat expansive soils for residential projects via deep injection. Due to the proprietary nature of the chemical stabilizers, there are very limited studies on the resilient modulus (MR) of chemically-treated expansive soils. This paper evaluates the effect of a liquid chemical stabilizer on the treatment of expansive soils collected from Texas and Colorado. The chemical solution, called ionic soil stabilizer (ISS) which contain sulfuric acid, phosphoric acid, citric acid, and water was used as an additive and tests were carried out on untreated and treated bulk soil samples in accordance with AASHTO T-307. The treated soil specimens were prepared by hand mixing the dry soils with the chemical stabilizer at three application ratios and two curing periods (7 and 28 days). The experiment results show that the value of resilient modulus increases with the increase of chemical application ratio. The resilient modulus of the trea...

Research paper thumbnail of Evaluation of Liquefaction Resistance in Silty Sand via Suction Controlled Cyclic Triaxial Tests

Research paper thumbnail of A Simplified Approach to Determine the Response of Unsaturated Soils Using Multistage Triaxial Test

Research paper thumbnail of Behavior of unsaturated cohesive-frictional soils over a whole range of suction/thermo-controlled stress paths and modes of deformation

Soils and Rocks

The present work documents some of the most recent experimental evidence of the thermohydro-mecha... more The present work documents some of the most recent experimental evidence of the thermohydro-mechanical behavior of compacted soils over a whole range of suction- and/or thermo-controlled stress paths and modes of deformation, including data from a series of triaxial, true triaxial, plane strain, ring shear, and resonant column tests conducted on different types of cohesive-frictional soils in the low-to-medium matric suction range under either room temperature or thermally controlled conditions. The work has been accomplished at the Advanced Geomechanics Laboratory of the University of Texas at Arlington, focusing primarily on the following essential features of unsaturated soil behavior: (1) Loading-collapse and apparent tensile strength loci assessed from suction-controlled triaxial and true triaxial testing on clayey sand, (2) Critical state lines from suction-controlled plane strain testing on silty soil, (3) Peak and residual failure envelopes from suction-controlled ring shear...

Research paper thumbnail of Assessment of Pavement Geometric Characteristics Using UAV-CRP Data

Research paper thumbnail of Response Of Unsaturated Silty Sand Over A Wider Range Of Suction States Using A Novel Double-walled Triaxial Testing System

RESPONSE OF UNSATURATED SILTY SAND OVER A WIDER RANGE OF SUCTION STATES USING A NOVEL DOUBLE-WALL... more RESPONSE OF UNSATURATED SILTY SAND OVER A WIDER RANGE OF SUCTION STATES USING A NOVEL DOUBLE-WALLED TRIAXIAL TESTING SYSTEM Ujwalkumar D. Patil, PhD The University of Texas at Arlington, 2014 Supervising Professor: Anand J. Puppala Co-Supervising Professor: Laureano R. Hoyos In recent decades, the state-of-the-art of our understanding of unsaturated soil performance has been considerably enhanced by the incorporation of novel and advanced features into the conventional testing devices such as direct shear device, ring shear device, triaxial device and true triaxial device. The novel suction-controlled triaxial system used in this research is fully automated and has enhanced features such as volume change device and double-walled cell to monitor the volume change accurately during all the stages of the unsaturated triaxial test. Despite their sophistication, such devices can help in testing mechanical behavior of unsaturated soils only up to the matric suction (s) value of 1500 kPa (...

Research paper thumbnail of Three-Dimensional Stability Analysis of Rock Slope Using Aerial Photogrammetry Data

Research paper thumbnail of Bioengineering Solution to Prevent Rainfall-Induced Slope Failures in Tropical Soil

Land, 2021

This paper presents test results of comprehensive laboratory and field-testing program efforts fo... more This paper presents test results of comprehensive laboratory and field-testing program efforts for the development of bioengineering solutions such as growing vegetation for protection of slopes from erosion and landslides in a tropical environmental setting. Saturated shear strength of soil was determined using direct shear tests and unsaturated soil properties, such as soil water retention curve (SWRC), were obtained using a computer-controlled hydraulic property analyzer (HYROP) system as well as a WP4C instrument. Climate data were obtained via field instrumentation and appropriate vegetation data were assumed to perform a finite element method-based transient seepage analysis and coupled slope stability analysis to test the potential of tropical hillslope to fail with and without vegetation over a period of one month. Results show that the factor of safety (FOS) for test slope considering case (a) the rainfall and bare ground, case (b) no rainfall with vegetation, and case (c) ...

Research paper thumbnail of Evaluation of Rock Slope Stability Using 3-Dimensional Data Analysis

Research paper thumbnail of Methodology for Resloping of Rock Slope Using 3D Models from UAV-CRP Technology

AbstractAssessing the stability of rock slopes is essential to ensuring the typical performance o... more AbstractAssessing the stability of rock slopes is essential to ensuring the typical performance of adjacent transportation infrastructures but simulating the existing field topography and boundary ...

Research paper thumbnail of Suction Stress Characteristic Curves of Cohesive-Frictional Soils from Multiple Suction-Controlled Testing Methods

International Journal of Geomechanics, 2020

In most geotechnical construction works, compacted soils of cohesive-frictional nature are expect... more In most geotechnical construction works, compacted soils of cohesive-frictional nature are expected to remain mostly under partially saturated conditions and hence experience continuous ch...

Research paper thumbnail of Effect of Rainfall Infiltration on Stability of a Tropical Slope from Western Pacific

Research paper thumbnail of Strength, Stiffness and Radial Anisotropy of Compacted Silty Sand Under Suction-Controlled Axisymmetric Shearing

Geotechnical and Geological Engineering

A thorough analysis of strength, stiffness, and stress-induced anisotropy of statically compacted... more A thorough analysis of strength, stiffness, and stress-induced anisotropy of statically compacted silty sand is presented based on results from a comprehensive suction-controlled (drained) triaxial test program. Induced soil suction values, via either axis-translation or relative humidity techniques, ranged between 0.05 to 300 MPa, with net confining pressures varying from 100 to 300 kPa. A relatively simple model/equation for peak friction angle (ϕpeak), over the entire test suction and net confinement range, is presented. As expected, peak strength response to suction-controlled monotonic shearing is influenced by the level of suction and net confining pressure, as well as the amount of dilatancy experienced by the silty sand. The nonlinear nature of the variation of deviator stress at peak and critical state conditions, with degree of saturation, was fitted reasonably well via fourth order and second order polynomial equations, respectively. A thorough analysis and modeling of stress-dilatancy behavior is presented in a companion paper. Finally, the inherent-anisotropy observed in the original soil fabric, as well as the stress induced-anisotropy observed in the sheared samples, are discussed based on results from suction-controlled isotropic consolidation and axisymmetric shearing, respectively; including the effect of suction on the rate of degradation of stiffness (moduli) of compacted silty sand under monotonic shearing.

Research paper thumbnail of Identifying hazardous obstructions within an intersection using unmanned aerial data analysis

International Journal of Transportation Science and Technology