A Framework for Liquefaction Susceptibility Mapping of Dhaka City Using Latest SPT Based Co-relationship and Regional Factors

Abstract

Integration of regional code-based provisions considering local site effects and updated analytical techniques is a must in the field of seismic site characterization and liquefaction susceptibility assessment. This study introduces provisions from latest regional guidelines to define seismic site class and assess liquefaction susceptibility, utilizing the most comprehensive database developed for Dhaka City and produces vulnerability maps, categorizing regions into various zones based on potential risk factors. Utilizing the latest SPT based co-relationship, coupled with code-based stress reduction factors, liquefaction susceptibility assessment was conducted. Additionally, classification-based supervised machine learning algorithms were utilized to evaluate the performance of the liquefaction susceptibility calculations, which were subsequently used as an input parameter for conducting geo-statistical interpolation, resulting in risk-based zonation maps in terms of liquefaction hazard for the city. The results show that the deposition type of soil plays a significant role in triggering liquefaction in different areas of Dhaka City and the majority portion of the recent artificial fill areas are subjected to high liquefaction potential for 7.0, 7.5 and 8.0 magnitude earthquake. This study also supplements the newly published mandates and provides guidelines according to the code to conduct engineering studies as per recommended seismic site class and liquefaction susceptibility for design applications. A significant increase in the coverage area of seismic site class with low shear wave velocities have been observed, necessitating special infrastructural considerations as per the new codal guidelines compared to past researches. Areas of improvement to evaluate liquefaction susceptibility in the newly published mandate also have been identified. Furthermore, this study also outlines a generalized framework with supplementary policies integrating regional factors into consideration for development of liquefaction susceptibility-based risk maps for any location. The developed liquefaction susceptibility-based zonation map provides a clear visual representation of areas prone to liquefaction, enabling better-informed decision- making for disaster preparedness, risk reduction, and sustainable urban development.