A Soil Stabilization technique: Biological Technique for Improving Clayey Soils

Environmentally Friendly soil methods are the most crucial matter for enhancing mechanical characteristics of the soils in the field of geotechnical engineering. For this reason, the authors applied new method which have been used in many scopes of engineering and so on. Microbial induced calcite precipitation (MICP) can produce bonding of calcite between soil grains leads to improve the mechanical properties of the soil. For this purpose, Sporosarsina Pasteurii strain have been blended with chloride so as to produce crystals of calcite betwixt clayey soil grains. The direct shear test has been performed on the treated and untreated soil samples which were classified as CL (according to unified soil classification). The results demonstrate the enhancement of friction angle and cohesion of the treated soil sample by comparison with the untreated sample. Becteria cell number which can be calculated by means of optical density (OD), has the most effect on the produced calcite amount. The Atterberg limits tests have been accomplished on treated and untreated soil samples to determine the effects of MICP on the double layer of clayey soil. The variation of treated sample’s liquid limit with respect to the untreated sample proves the process of MICP. Scaning electron microscope (SEM) have been taken from the treated sample in order to verify the presence of calcite’s crystals. Whole of tests demonstrate that MICP technique can be very beneficial in view of two reasons; high-leveled performance of Sporosarsina Pasteurii and the latter reason is environmentally friendly process that the calcite precipitation does not have detrimental impacts on the natural medium of soil.

Keywords:

Sporosarsina Pasteurii , optical density , Biological technique , improvement