2024
Browse
Item Evaluation of Shear Wave Velocity for Different Locations in Dhaka City & Seismic Site Response Analysis using DEEPSOIL(Department of Civil and Environmental Engineering(CEE), Islamic University of Technology(IUT), Board Bazar, Gazipur-1704, Bangladesh, 2024-07-09) Rahman, Faria; Chowdhury, Md. Abdul Mubin; Chowdhury, Md. SakibDhaka, the capital of Bangladesh, is one of the world's most seismically vulnerable cities due to its proximity to the convergent boundary of the Eurasian and Indian tectonic plates. This vulnerability is exacerbated by factors such as uncontrolled urban expansion, non-engineered construction practices, high population density, and a weak emergency response system. The city is situated on an elevated Pleistocene terrace surrounded by Holocene floodplains, with the terrace comprising Pleistocene clayey soils and the floodplains consisting of alluvial sandy and clayey deposits. To conduct site-specific seismic hazard analysis, it is crucial to estimate the amplification factors of seismic waves, which requires determining the average shear wave velocity of the near-surface soils up to a depth of 30 meters. In Dhaka, Vs30 has been estimated using techniques such as multichannel analysis of surface waves (MASW), microtremor array measurement (MAM) survey, and empirical correlations between shear wave velocity and standard penetration test blow count. Another important concept in earthquake studies is liquefaction, which refers to the loss of strength and stiffness in saturated, loose sandy soils during ground shaking, leading to severe structural damage. The correlation between shear wave velocity and SPT-N has been analyzed using field test data. Nonlinear site response analysis has been performed with DEEPSOIL software to evaluate potential seismic hazards at the ground. The Peak Ground Acceleration has been obtained to assess the likelihood of liquefaction based on the ground condition. Using borehole data, the research area has been divided into three different groups to account for local site impacts and calculate seismicity characteristics using the Bangladesh National Building Code. Ground motions on specific site classes recorded in other regions with similar magnitude earthquakes were included in this analysis. A hyperbolic model was used to fit the shear modulus and damping curves to represent ground motions under high-strain conditions. The PGA forecasted in this study will inform the safe design of structures and the proper planning of significant infrastructure projects