Evaluation of Foundation Difficulties over Soft Organic Soil

Over the past 50 years, Dhaka, the Capital of Bangladesh, has experienced a rapid growth of urban population. This high population increase demands rapid expansion of the city. Unfortunately, most parts of Dhaka having competent subsoil for building construction are already exhausted. As such, new areas are being reclaimed by both government and private agencies using dredged fill from nearby river sources. A very soft organic layer exists below the filling layer that is highly plastic and highly compressible. SPT Nvalues of filling layer and organic layer vary from 2 to 11 and 1 to 2, respectively. It is observed that settlement of the organic layer varied from about 242 mm to 637 mm in between 1.8 to 12.7 years, respectively, due to overburden pressure of 100 kPa. Moreover, the existing organic layer may cause negative skin friction to the pile foundation and make foundation difficulties.