Ground Response Analysis of a Reclaimed Coastal Site using DEEPSOIL

Abstract

Earthquakes are among the most destructive natural hazards, causing extensive damage to infrastructure and significant economic losses worldwide. The severity of earthquake-induced damage is strongly influenced by local site conditions, including soil stratigraphy, stiffness contrast, and nonlinear soil behavior, which can substantially amplify seismic ground motions. This study presents a detailed one-dimensional ground response analysis of a reclaimed coastal site located in Matarbari, Moheshkhali, Cox’s Bazar, Bangladesh, using the DEEPSOIL software platform. The analysis incorporated key response parameters such as response spectra, acceleration time histories, Peak Ground Acceleration (PGA), shear strain distribution, and shear stress ratio with depth. Two well-documented historical earthquake records as the 1995 Kobe earthquake and the 1999 Chi-Chi earthquake were used as input motions to assess the influence of different frequency contents and shaking intensities on local site response. The equivalent linear method was employed to assess site amplification, evaluating response spectra, strain time histories, Peak Ground Acceleration (PGA), and maximum strain with depth. The study’s findings highlight the variations in spectral acceleration and time periods across different borehole locations, emphasizing the influence of local soil conditions. Varying boreholes recorded different PGAs for the same earthquake motion, with some locations exhibiting surface soil responses exceeding the input motion, primarily due to the presence of residual soils like ‘Fat clay.’ The results indicate a high susceptibility to earthquakes such as the Kobe and Chi-Chi earthquakes, underscoring the need for meticulous earthquake-resistant design in such regions.