Some studies of strip footing on granular bed overlying weak soil

Abstract

An increasing proportion of building development takes place on poor and difficult ground which presents the Geotechnical Engineer with the challenge of providing satisfactory foundation performance. Ground behaviour can be modified by ground treatment / improvement so that ground properties are improved. Ground improvement can be defined as the controlled alteration of the state, nature or mass behaviour of ground materials in order to achieve an intended satisfactory response to existing or projected environmental and engineering actions. Improving the load carrying capacity of a soft soil by providing a blanket of sand/gravel on it is a proven technique. A compacted granular bed laid over soft soil improves the bearing capacity and settlement response of footing placed over latter. Thus this technique, apart from being widely used beneath embankments, is also used to improve the bearing capacity of foundation soils for light to moderately loaded structures. This paper presents a study of load transfer mechanism and bearing capacity behaviour of a strip footing on granular bed overlying weak shedi soil. The experimental investigations were conducted in laboratory to study the behaviour of model strip footing of various widths on granular bed of varying thickness overlying weak soft soil at various water contents and densities. It is concluded that shedi soil behaves as a weak soil from shear strength tests conducted in laboratory and also from model load tests. Only for the case of model footing resting directly on soil, punching shear failure is most likely to occur. Providing a layer of granular bed (quarry dust) over the soft soil increases its bearing capacity by about 30 to 50%. As the thickness of granular bed increases, the influence width due to loading at soil-granular bed interface also increases as observed from the settlement profile. Research India Publications.