Geologically, the Dhaka-Tongi area consists of parts of high inlier, along narrow tract of older sediments hosting the major parts of the city and surrounded by very young riverine sediments occupying the surrounding valleys. The drainage... more
Geologically, the Dhaka-Tongi area consists of parts of high inlier, along narrow tract of older sediments hosting the major parts of the city and surrounded by very young riverine sediments occupying the surrounding valleys. The drainage patterns of this tract consist of two types, dendritic and trellis. The older sediment sequence consists of sandstone of Dupi Tila Formation overlain by by the Madhupur Clay. The Clay is overlain by alluvium, but is locally exposed in stream valleys. The region can be divided into three types of landforms – a central high area, a complex of high and lowareas band a complex of low areas. The ground condition with respect to construction can be rated as: favourable, poor and hazardous. The techniques for ground improvement depend on the ground conditions which are intimately related to the geology (sediment type and structure) and geomorphology (landform and elevation). The type of site preparation techniques applicable during pre-construction development are variable from simple removal of the surficial soft soil followed by a sand fill and compaction to more complex techniques of using geotextile, grouting, preloading and surcharge. Taking account of above, a model is suggested which can be used to choose the appropriate ground improvement technique.
