Seismic Stability and Deformation Analysis of a South India Hill Slope by Finite Elements

The seismic stability analysis of slopes is frequently analyzed using the method of slices based on the pseudostatic approach. However, the time response analysis is considered to be one of the most competent tools to analyze the performance of slopes under seismic motion since this method provides details about deformation and stress distribution within the slope. In this paper, a finite-element-based time response analysis was performed to examine the seismic response of an existing hill slope located in the Kavalappara (11.414 degrees N, 76.237 degrees E) region of Kerala, India, where the shear strength of many slopes reduces considerably due to heavy rainfall. In this regard, a synthetic acceleration time history was developed from site-specific seismic hazard analysis. Also, a pseudostatic analysis based on the finite-element method was performed to estimate the factor of safety and corresponding stability measure. The finite-element model was developed based on Mohr-Coulomb and hardening soil with small stiffness (HSsmall) constitutive models to capture the soil behavior during an earthquake. Further, Newmark's sliding block analysis was conducted analytically to study the probable displacement after the seismic event and to validate the present finite-element analysis results. The pseudostatic analysis revealed that the slope is not safe against a pseudostatic loading of 0.12g. The seismic response of the slope under earthquake motion was described via displacement developed due to ground shaking. The results of time response indicated a continuous forward and downward earthquake-induced movement of the slope crest. The maximum displacement observed during the seismic event was 18.84 mm. Further, a sensitivity analysis was performed by considering Newmark's method and a few well-known empirical methods to check the variation of FS values with yield acceleration. Displacement and factor of safety values calculated using analytical methods were in good agreement with that obtained from finite-element-based time response analysis. Moreover, it has been concluded that there is potentially unstable slope condition exists due to combined groundwater variations and earthquake impact. (c) 2022 American Society of Civil Engineers.