DAMAGE MECHANISM IN PROBLEMATIC SOILS

Any structure constructed on the earth is supported by soil underlying it. Foundation is an interfacing element between superstructure and the underlying soil that transmits the loads supported by the foundation and it's self-weight. Foundation design requires evaluation of safe bearing capacity both immediate and long term settlement. The weak and compressible soils are subjected to problems related to bearing capacity and settlement. Different degrees of precaution are to be taken to implement a given design without causing any distress to adjoining structures. It is equally important to determine problems anticipated during construction and work out proper construction procedure and remedial measures in time. The construction problems may vary from site to site and many problems are site specific. Expansive soils seriously affect various structures that are founded on them due to their tendency to undergo shrinkage and swelling with seasonal moisture fluctuations. Identification and understanding of these soils are required to safeguard the existing and future constructions. Similarly differential movement of foundations of structures is a common problem in problematic soil, due to changes in moisture content of soil below the foundation. In the present paper, an attempt is made to throw light on some general problems associated with foundation constructions and improvement techniques for safe design of foundations in problematic soils such as expansive soils and soft soils. The general characteristics of expansive soils and basis for identification have been also discussed in detailed. Damage potential of expansive soils with respect to different civil engineering constructions have been explained with suitable illustrations and the causes for volume change phenomena of expansive soils have been discussed. Various available techniques for minimizing the swelling of soils and various options for foundation laying have also been presented. Thus it can be concluded that by using suitable improvement techniques and proper design of different components it is possible to construct safe, stable and economical structure.