Date of Award
Doctor of Philosophy (PhD)
Ronald D. Andrus
Kalyan R. Piratla
Failure of geotechnical systems during hydroclimatic events such as heavy rainfall, flood, and drought often leads to significant socio-economic loss. The time-dependent stability and deformation behaviors of geotechnical systems subjected to hydroclimatic events must be investigated using a coupled flow-deformation formulation because the strength and deformation parameters vary with the degree of saturation and/or matric suction of the soil. Although the impacts of the hydroclimatic events on the geotechnical systems are assessed and summarized in the previous studies, all the analyses were carried out in a loosely coupled manner and/or uncoupled manner without considering the effects of water flow in the deformation and failure of the systems. Therefore, in this study, the accuracy of PLAXIS 2D in predicting the deformation behavior of geotechnical systems was improved by modifying a widely used constitutive model, the Mohr-Coulomb model. The model was improved by updating the elastic modulus and the yield criterion based on the degree of saturation and/or matric suction of the soil element. The modified model was implemented within PLAXIS 2D as a user-defined constitutive model to analyze the performance of shallow foundations, deep foundations, and earth slopes under hydroclimatic events.
Although the hydroclimatic events alone can cause socio-economic losses, recent records show that multiple hazards such as rainfall-excavation, rainfall-earthquake, rainfall-toe-erosion induced by flood, etc., can occur simultaneously and induce catastrophic damages to life and properties. The impacts of multi-hazards must be understood using coupled flow-deformation code to reduce the losses. In this study, first, the stability and deformation behavior of earth slopes subjected to the individual and simultaneous occurrence of heavy rainfall, toe-erosion induced by flood, earthquake, and toe excavation were investigated using a coupled finite element code PLAXIS. Then, the performance of buried concrete pipe subjected to flooding due to heavy rainfall, infiltration of flood water, leakage of the pipe, and soil erosion as a result of pipe failure were evaluated using PLAXIS. The analyses provide a valuable reference for identifying and assessing potential hazardous scenarios to formulate disaster prevention and mitigation strategies related to slopes and buried pipes.
Finally, the finite element results were combined with probabilistic methods to predict the stability of earth slopes, considering possible variations in soil properties and hydroclimatic event parameters. The response surface for the stability of the slope was created using the soil properties and hydroclimatic events as random variables. Further, the created response surface was used to calculate the probability of failure of slopes subjected to hydroclimatic events using the Monte-Carlo simulation method (MCSM) and the first-order reliability method (FORM. The proposed framework can evaluate the performance level of slopes subjected to rainfall with the aid of the failure probability of slopes.
Vickneswaran, Tharshikka, "Performance of Geotechnical Systems Under Extreme Hydroclimatic Events Using Finite Element Modeling" (2022). All Dissertations. 3003.
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