Earthquake Induced Liquefaction Potential of Reclaimed Areas of Dhaka City

Historical seismicity data and recent seismic activities in and around Bangladesh indicate that Bangladesh is at high seismic risk. The capital city Dhaka is situated in the seismic Zone 2, which has a basic seismic coefficient of 0.15g. Over the past 40 years, Dhaka city has experienced a rapid growth of urban population. This high population increase demands rapid expansion of the city. Unfortunately, most parts of the original ground have already been occupied. As a result, both government and private agencies are reclaiming different new areas. In most cases, the practice for developing such areas is just to fill lowlands (3~12 m) by dredged material, which is almost silty sand. This is inviting great liquefaction susceptibility for such reclaimed areas. The field SPT N-value of the filling depth varies from 1 to 13. Mean particle diameter and fines content of the fill materials vary from 0.10~0.32 mm and 6~48%, respectively. Liquefaction potential of selected reclaimed areas of the city has been estimated based on standard penetration test and shear wave velocity. It is found that some parts of the reclaimed sites are susceptible to liquefaction up to the filling depth.