Effect of High Peak Ground Acceleration on the Liquefaction Behaviour of Subsoil and Impact on the Environment

摘要

Although liquefaction of soil is a function of soil condition but the effect of Peak Ground Acceleration (PGA) is obvious. A total of ten boreholes were selected in the Mohammadpur, Dhaka, Bangladesh for the study. Liquefaction potential at three different levels (3, 6 and 10 m) and for three different PGA of 0.15 g, 0.30 g and 0.47 g was estimated. Liquefaction maps were drawn by using Arc GIS software and the vulnerability due to liquefaction was categorized into three different names as liquefiable, marginally liquefiable and non-liquefiable. By analyzing the liquefaction maps a risk assessment of the study area has been done in this research. The liquefaction maps reveal a bird's eye view of the whole research project. High PGA value results in a high susceptibility to liquefaction. For a PGA of 0.47g the study areas are highly vulnerable in case of liquefaction at all levels. Although Mohammadpur as well as Dhaka is in the earthquake zone 2 with zone coefficient of 0.15 but it could be in danger if high PGA occurs. So it is of great concern. High PGA values should be taken into consideration during designing any structure in the study area and existing design should be modified as PGA is a dominant factor. An Environmental Impact Assessment (EIA) of the hazard due to liquefaction was also done which indicates that Strong ground shaking associated with a large earthquake on a nearby fault in the study area could trigger soil liquefaction and associated ground failures the impact of which would be significant.