{"id":{"repo_id":"vt","oai_identifier":"oai:vtechworks.lib.vt.edu:10919/135430"},"canonical_url":"https://search.dev.ndltd.org/etd/vt/oai:vtechworks.lib.vt.edu:10919/135430","repository":{"repo_id":"vt","name":"Virginia Tech","base_url":"https://vtechworks.lib.vt.edu/oai/request"},"display":{"title":"Terramechanics of Saturated Clays: Assessing Tire Performance Through Experimental and Numerical Approaches","abstract":"As autonomy begins to be integrated into combat vehicles, the necessity for high-fidelity virtual proving grounds becomes imperative. Performance prediction tools capable of accurately predicting drawbar performance and sinkage are useful for path prediction and navigation without the loss of mobility. This thesis focuses on formulating the physics underlying such predictive tools, particularly in the challenging terrain of saturated clays. Modeling cohesive soils with high water content is challenging due to their low shear strength and highly deformable nature, necessitating systematic consideration in both material modeling and numerical techniques. Saturated clay is marked by high plasticity, considerable deformability, and history-dependent effects, leading to non-linear behavior under various loading scenarios. Notably, under the substantial shear loads exerted by the tire, estimating the yielding mechanism and residual strength of the clay is crucial for multipass scenarios. From a fundamental soil mechanics perspective, the pore water pressure that accumulates in the soil significantly influences this performance, yet it remains underexplored. The rapid shear loading experienced by the soil can result in changes in pore water pressure of the soil, which may take extended periods to recover. To address this, an investigation of the time-scale effect with tire passes is considered. This study will differentiate between the short-term effects of a single pass and immediate multipass scenarios, compared to the multipass effect observed after a substantial duration, allowing for pore water dissipation. To illustrate this theory, this thesis emphasizes experimental and modeling techniques aimed at capturing the influence of pore water. The soil is characterized through geotechnical tests, and different material models are developed based on these findings. The impact of the soil constitutive law on the overall tire-soil simulations is examined, considering both total and effective stress frameworks. Additionally, different numerical techniques and their corresponding solutions are investigated. A user-defined material model, grounded in critical state soil mechanics with post-yielding softening effects, is proposed to represent the residual conditions of the soil fabric in tire-soil interactions. Complementarily, an advanced FE tire model is developed for tire mobility studies. Full-scale testing is conducted on a terramechanics tire-soil bin rig at Virginia Tech to validate both the FE tire model and the tire-clay interaction model. Cone Penetration Test (CPT) results are simulated to verify the in situ conditions of the soil. This tire-soil testing is carried out over a two-week period, facilitating the evaluation of time-scale effects on drawbar pull, sinkage, and rut formation in the soil. Ultimately, the insights gained from this research aim to enhance the physics and predictive capabilities of simulation tools, thereby supporting the development of virtual proving grounds and test beds for challenging terrains","abstract_html":"As autonomy begins to be integrated into combat vehicles, the necessity for high-fidelity virtual proving grounds becomes imperative. Performance prediction tools capable of accurately predicting drawbar performance and sinkage are useful for path prediction and navigation without the loss of mobility. This thesis focuses on formulating the physics underlying such predictive tools, particularly in the challenging terrain of saturated clays. Modeling cohesive soils with high water content is challenging due to their low shear strength and highly deformable nature, necessitating systematic consideration in both material modeling and numerical techniques. Saturated clay is marked by high plasticity, considerable deformability, and history-dependent effects, leading to non-linear behavior under various loading scenarios. Notably, under the substantial shear loads exerted by the tire, estimating the yielding mechanism and residual strength of the clay is crucial for multipass scenarios. From a fundamental soil mechanics perspective, the pore water pressure that accumulates in the soil significantly influences this performance, yet it remains underexplored. The rapid shear loading experienced by the soil can result in changes in pore water pressure of the soil, which may take extended periods to recover. To address this, an investigation of the time-scale effect with tire passes is considered. This study will differentiate between the short-term effects of a single pass and immediate multipass scenarios, compared to the multipass effect observed after a substantial duration, allowing for pore water dissipation. To illustrate this theory, this thesis emphasizes experimental and modeling techniques aimed at capturing the influence of pore water. The soil is characterized through geotechnical tests, and different material models are developed based on these findings. The impact of the soil constitutive law on the overall tire-soil simulations is examined, considering both total and effective stress frameworks. Additionally, different numerical techniques and their corresponding solutions are investigated. A user-defined material model, grounded in critical state soil mechanics with post-yielding softening effects, is proposed to represent the residual conditions of the soil fabric in tire-soil interactions. Complementarily, an advanced FE tire model is developed for tire mobility studies. Full-scale testing is conducted on a terramechanics tire-soil bin rig at Virginia Tech to validate both the FE tire model and the tire-clay interaction model. Cone Penetration Test (CPT) results are simulated to verify the in situ conditions of the soil. This tire-soil testing is carried out over a two-week period, facilitating the evaluation of time-scale effects on drawbar pull, sinkage, and rut formation in the soil. Ultimately, the insights gained from this research aim to enhance the physics and predictive capabilities of simulation tools, thereby supporting the development of virtual proving grounds and test beds for challenging terrains","abstract_has_math":false,"creators":["Swamy, Varsha S."],"institution":"Virginia Tech","degree_name":"Doctor of Philosophy","degree_level":"doctoral","degree_discipline":"Mechanical Engineering","degree_department":"Mechanical Engineering","school":null,"contributors":[],"advisors":[],"committee_chairs":["Sandu, Corina","Yerro Colom, Alba"],"committee_members":["Ferris, John B.","Taheri, Saied","Warfford, Jeffrey Thomas","Sebeck, Katherine M."],"year":2025,"date_issued":"2025-06-09","date_published":"2025-06-09","updated_at":"2026-07-22T22:19:03Z","subjects":["terramechanics","tire-soil interaction","soil modeling","tire modeling","FEA","SPH"],"languages":["en"],"rights":["In Copyright"],"rights_urls":["http://rightsstatements.org/vocab/InC/1.0/"],"identifier_entries":[{"key":"dc:identifier.other","label":"Dc Identifier Other","values":["vt_gsexam:43748"],"render_values":[{"text":"vt_gsexam:43748","href":null,"code":true}]}]},"links":{"outbound_url":"https://hdl.handle.net/10919/135430","outbound_label":"Handle","outbound_source":"dc:identifier.uri"},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:contributor.committeechair","label":"Committee Chair","values":["Sandu, Corina","Yerro Colom, Alba"]},{"key":"dc:contributor.committeemember","label":"Committee Member","values":["Ferris, John B.","Taheri, Saied","Warfford, Jeffrey Thomas","Sebeck, Katherine M."]},{"key":"dc:contributor.department","label":"Department","values":["Mechanical Engineering"]},{"key":"dc:creator","label":"Author","values":["Swamy, Varsha S."]}]},{"id":"academic_context","label":"Academic Context","entries":[{"key":"dc:date.accessioned","label":"Dc Date Accessioned","values":["2025-06-10T08:01:04Z"]},{"key":"dc:date.available","label":"Dc Date Available","values":["2025-06-10T08:01:04Z"]},{"key":"dc:date.issued","label":"Date","values":["2025-06-09"]},{"key":"dc:publisher","label":"Institution","values":["Virginia Tech"]},{"key":"dc:type","label":"Dc Type","values":["Dissertation"]},{"key":"thesis:degree_discipline","label":"Discipline","values":["Mechanical Engineering"]},{"key":"thesis:degree_level","label":"Degree Level","values":["doctoral"]},{"key":"thesis:degree_name","label":"Degree Name","values":["Doctor of Philosophy"]},{"key":"thesis:institution_name","label":"Thesis Institution Name","values":["Virginia Polytechnic Institute and State University"]}]},{"id":"subjects_keywords","label":"Subjects and Keywords","entries":[{"key":"dc:subject","label":"Dc Subject","values":["terramechanics","tire-soil interaction","soil modeling","tire modeling","FEA","SPH"]}]},{"id":"language_rights","label":"Language and Rights","entries":[{"key":"dc:language.iso","label":"Language (ISO)","values":["en"]},{"key":"dc:rights","label":"Dc Rights","values":["In Copyright"]},{"key":"dc:rights.uri","label":"Rights URI","values":["http://rightsstatements.org/vocab/InC/1.0/"]}]},{"id":"identifiers","label":"Identifiers","entries":[{"key":"dc:identifier.other","label":"Dc Identifier Other","values":["vt_gsexam:43748"]},{"key":"dc:identifier.uri","label":"Identifier URI","values":["https://hdl.handle.net/10919/135430"]}]},{"id":"additional","label":"Additional Metadata","entries":[{"key":"dc:description.abstract","label":"Abstract","values":["As autonomy begins to be integrated into combat vehicles, the necessity for high-fidelity virtual proving grounds becomes imperative. Performance prediction tools capable of accurately predicting drawbar performance and sinkage are useful for path prediction and navigation without the loss of mobility. This thesis focuses on formulating the physics underlying such predictive tools, particularly in the challenging terrain of saturated clays. Modeling cohesive soils with high water content is challenging due to their low shear strength and highly deformable nature, necessitating systematic consideration in both material modeling and numerical techniques. Saturated clay is marked by high plasticity, considerable deformability, and history-dependent effects, leading to non-linear behavior under various loading scenarios. Notably, under the substantial shear loads exerted by the tire, estimating the yielding mechanism and residual strength of the clay is crucial for multipass scenarios. From a fundamental soil mechanics perspective, the pore water pressure that accumulates in the soil significantly influences this performance, yet it remains underexplored. The rapid shear loading experienced by the soil can result in changes in pore water pressure of the soil, which may take extended periods to recover. To address this, an investigation of the time-scale effect with tire passes is considered. This study will differentiate between the short-term effects of a single pass and immediate multipass scenarios, compared to the multipass effect observed after a substantial duration, allowing for pore water dissipation. To illustrate this theory, this thesis emphasizes experimental and modeling techniques aimed at capturing the influence of pore water. The soil is characterized through geotechnical tests, and different material models are developed based on these findings. The impact of the soil constitutive law on the overall tire-soil simulations is examined, considering both total and effective stress frameworks. Additionally, different numerical techniques and their corresponding solutions are investigated. A user-defined material model, grounded in critical state soil mechanics with post-yielding softening effects, is proposed to represent the residual conditions of the soil fabric in tire-soil interactions. Complementarily, an advanced FE tire model is developed for tire mobility studies. Full-scale testing is conducted on a terramechanics tire-soil bin rig at Virginia Tech to validate both the FE tire model and the tire-clay interaction model. Cone Penetration Test (CPT) results are simulated to verify the in situ conditions of the soil. This tire-soil testing is carried out over a two-week period, facilitating the evaluation of time-scale effects on drawbar pull, sinkage, and rut formation in the soil. Ultimately, the insights gained from this research aim to enhance the physics and predictive capabilities of simulation tools, thereby supporting the development of virtual proving grounds and test beds for challenging terrains"]},{"key":"dc:description.abstractgeneral","label":"General Abstract","values":["The mobility of ground vehicles in challenging off-road environments poses a significant problem. Unlike vehicles on paved roads, where the surface is stable and rigid, off-road vehicles must operate on terrain that deforms around the tires, increasing resistance and making movement more difficult. This area of study, known as terramechanics, plays a critical role in understanding how vehicles like military tanks, agricultural machinery, and earthmoving equipment operate in such hostile conditions. One of the key challenges in this field is predicting whether a vehicle will be able to move effectively (\"GO\") or become immobilized (\"NOGO\") based on factors like soil strength, vehicle speed, and weight. Additionally, quantifying vehicle performance in terms of traction and developing models that accurately represent the physics of these interactions is essential for improving off-road mobility and creating reliable performance prediction tools. This thesis addresses a particularly challenging terrain condition that has been underexplored in the literature: the mobility of ground vehicles on wet or saturated cohesive soils, commonly known as mud. Mud is a type of highly saturated clay soil that is cohesive, highly plastic, and exhibits liquid-like behavior, often characterized by splashing and sloshing. With its low shear strength, mud presents one of the worst-case scenarios for ground vehicles and may lead to the loss of traction or complete immobilization due to excessive sinkage. The primary research question of the thesis centers on analyzing the influence of pore water on soil mobility, specifically when subjected to the forces of compression and shear from a tire. Additionally, this project will address the impact of time on the performance and rutting, focusing on both short-term effects from a single tire pass and immediate multipass scenarios, as well as the long-term consequences of multipass after a significant time lapse. The approach of this work combines both computational modeling and experimentation to better understand tire-clay interaction, particularly under conditions of high plasticity and large deformations. A novel mud material model is developed and proposed as a solution to the current limitations of models present in the literature. These models are validated using experimental data from controlled tests in the indoor soil bin. A key advancement in this research lies in modeling the soil and water as separate entities and then coupling them, following the effective stress framework—a significant contribution to tire-terrain interaction studies. Various soil material models, ranging from basic to advanced, are tested alongside an advanced finite element model of a bias-ply tire. The simulations generate different slip ratios to evaluate the tire's drawbar pull and sinkage. On the experimental side, saturated clay is subjected to a series of ten tire passes over two weeks to examine the time effects on the terrain. The final results from both, the simulations and experiments, are compared to assess the model's robustness and accuracy, offering key insights into the validity of the methodology and its potential applications in supporting the modeling and simulation of virtual proving grounds."]},{"key":"dc:description.degree","label":"Dc Description Degree","values":["Doctor of Philosophy"]},{"key":"dc:format.medium","label":"Dc Format Medium","values":["ETD"]},{"key":"dc:title","label":"Title","values":["Terramechanics of Saturated Clays: Assessing Tire Performance Through Experimental and Numerical Approaches"]}]}],"canonical_facts":{"dc:contributor.committeechair":["Sandu, Corina","Yerro Colom, Alba"],"dc:contributor.committeemember":["Ferris, John B.","Taheri, Saied","Warfford, Jeffrey Thomas","Sebeck, Katherine M."],"dc:contributor.department":["Mechanical Engineering"],"dc:creator":["Swamy, Varsha S."],"dc:date.accessioned":["2025-06-10T08:01:04Z"],"dc:date.available":["2025-06-10T08:01:04Z"],"dc:date.issued":["2025-06-09"],"dc:description.abstract":["As autonomy begins to be integrated into combat vehicles, the necessity for high-fidelity virtual proving grounds becomes imperative. Performance prediction tools capable of accurately predicting drawbar performance and sinkage are useful for path prediction and navigation without the loss of mobility. This thesis focuses on formulating the physics underlying such predictive tools, particularly in the challenging terrain of saturated clays. Modeling cohesive soils with high water content is challenging due to their low shear strength and highly deformable nature, necessitating systematic consideration in both material modeling and numerical techniques. Saturated clay is marked by high plasticity, considerable deformability, and history-dependent effects, leading to non-linear behavior under various loading scenarios. Notably, under the substantial shear loads exerted by the tire, estimating the yielding mechanism and residual strength of the clay is crucial for multipass scenarios. From a fundamental soil mechanics perspective, the pore water pressure that accumulates in the soil significantly influences this performance, yet it remains underexplored. The rapid shear loading experienced by the soil can result in changes in pore water pressure of the soil, which may take extended periods to recover. To address this, an investigation of the time-scale effect with tire passes is considered. This study will differentiate between the short-term effects of a single pass and immediate multipass scenarios, compared to the multipass effect observed after a substantial duration, allowing for pore water dissipation. To illustrate this theory, this thesis emphasizes experimental and modeling techniques aimed at capturing the influence of pore water. The soil is characterized through geotechnical tests, and different material models are developed based on these findings. The impact of the soil constitutive law on the overall tire-soil simulations is examined, considering both total and effective stress frameworks. Additionally, different numerical techniques and their corresponding solutions are investigated. A user-defined material model, grounded in critical state soil mechanics with post-yielding softening effects, is proposed to represent the residual conditions of the soil fabric in tire-soil interactions. Complementarily, an advanced FE tire model is developed for tire mobility studies. Full-scale testing is conducted on a terramechanics tire-soil bin rig at Virginia Tech to validate both the FE tire model and the tire-clay interaction model. Cone Penetration Test (CPT) results are simulated to verify the in situ conditions of the soil. This tire-soil testing is carried out over a two-week period, facilitating the evaluation of time-scale effects on drawbar pull, sinkage, and rut formation in the soil. Ultimately, the insights gained from this research aim to enhance the physics and predictive capabilities of simulation tools, thereby supporting the development of virtual proving grounds and test beds for challenging terrains"],"dc:description.abstractgeneral":["The mobility of ground vehicles in challenging off-road environments poses a significant problem. Unlike vehicles on paved roads, where the surface is stable and rigid, off-road vehicles must operate on terrain that deforms around the tires, increasing resistance and making movement more difficult. This area of study, known as terramechanics, plays a critical role in understanding how vehicles like military tanks, agricultural machinery, and earthmoving equipment operate in such hostile conditions. One of the key challenges in this field is predicting whether a vehicle will be able to move effectively (\"GO\") or become immobilized (\"NOGO\") based on factors like soil strength, vehicle speed, and weight. Additionally, quantifying vehicle performance in terms of traction and developing models that accurately represent the physics of these interactions is essential for improving off-road mobility and creating reliable performance prediction tools. This thesis addresses a particularly challenging terrain condition that has been underexplored in the literature: the mobility of ground vehicles on wet or saturated cohesive soils, commonly known as mud. Mud is a type of highly saturated clay soil that is cohesive, highly plastic, and exhibits liquid-like behavior, often characterized by splashing and sloshing. With its low shear strength, mud presents one of the worst-case scenarios for ground vehicles and may lead to the loss of traction or complete immobilization due to excessive sinkage. The primary research question of the thesis centers on analyzing the influence of pore water on soil mobility, specifically when subjected to the forces of compression and shear from a tire. Additionally, this project will address the impact of time on the performance and rutting, focusing on both short-term effects from a single tire pass and immediate multipass scenarios, as well as the long-term consequences of multipass after a significant time lapse. The approach of this work combines both computational modeling and experimentation to better understand tire-clay interaction, particularly under conditions of high plasticity and large deformations. A novel mud material model is developed and proposed as a solution to the current limitations of models present in the literature. These models are validated using experimental data from controlled tests in the indoor soil bin. A key advancement in this research lies in modeling the soil and water as separate entities and then coupling them, following the effective stress framework—a significant contribution to tire-terrain interaction studies. Various soil material models, ranging from basic to advanced, are tested alongside an advanced finite element model of a bias-ply tire. The simulations generate different slip ratios to evaluate the tire's drawbar pull and sinkage. On the experimental side, saturated clay is subjected to a series of ten tire passes over two weeks to examine the time effects on the terrain. The final results from both, the simulations and experiments, are compared to assess the model's robustness and accuracy, offering key insights into the validity of the methodology and its potential applications in supporting the modeling and simulation of virtual proving grounds."],"dc:description.degree":["Doctor of Philosophy"],"dc:format.medium":["ETD"],"dc:identifier.other":["vt_gsexam:43748"],"dc:identifier.uri":["https://hdl.handle.net/10919/135430"],"dc:language.iso":["en"],"dc:publisher":["Virginia Tech"],"dc:rights":["In Copyright"],"dc:rights.uri":["http://rightsstatements.org/vocab/InC/1.0/"],"dc:subject":["terramechanics","tire-soil interaction","soil modeling","tire modeling","FEA","SPH"],"dc:title":["Terramechanics of Saturated Clays: Assessing Tire Performance Through Experimental and Numerical Approaches"],"dc:type":["Dissertation"],"thesis:degree_discipline":["Mechanical Engineering"],"thesis:degree_level":["doctoral"],"thesis:degree_name":["Doctor of Philosophy"],"thesis:institution_name":["Virginia Polytechnic Institute and State University"]},"updated_at":"2026-07-22T22:19:03Z"}