A study on the engineering behaviour of grouted loose sandy soils

Abstract

The constructional activities in the coastal belt of our country often demand deep foundations because of the poor engineering properties and the related problems arising from weak soil at shallow depths. The soil profile in coastal area often consists of very loose sandy soils extending to a depth of 3 to 4 m from the ground level underlain by clayey soils of medium consistency. The very low shearing resistance of the foundation bed causes local as well as punching shear failure. Hence structures newlinebuilt on these soils may suffer from excessive settlements. This type of soil profile is very common in coastal areas of Kerala, especially in Cochin. Further, the high water table and limited depth of the top sandy layer in these areas restrict the depth of foundation thereby further reducing the safe bearing capacity. The present investigation was aimed at obtaining solutions for problems like this. The improvement in relative density and thereby the load carrying capacity of loose sandy soils of different gradations through different methods such as vibration newlinetechnique was studied. The low values of bearing capacity estimated even after newlinedensification compared to the requirement in the case of foundations for multi-storey newlinebuildings prompted to try grouting as one of the possible solutions. Grouting is quite a familiar term in foundation engineering, the primary purpose of which is to fill the voids of the formation material by replacing the existing fluids/air with the grout and thereby improving the engineering properties of the medium. The most commonly used grout material i.e. - ordinary Portland cement - newlinehas many advantages such as high strength, high durability, environmently free and newlineof low cost. Two methods were adopted to place the grout within the pores of the newlinesand medium. They are: (i) by hand mixing the grout uniformly with the soil and (ii) newlineby pumping the grout into the sand medium with the help of a grout pump.