EFFECT OF MICROBIAL INDUCED CALCITE PRECIPITATE ON SHEAR STRENGTH PARAMETERS OF WEAK CLAYEY SOIL

Abstract

Soil improvement is a key factor when dealing with weak soils in civil engineering works. Conventional soil improvement methods have negative effects on human health and environment which results in the new innovation for soil improvement. Microbial induced calcite precipitation involves the use of bioactivity which involves the introduction of calcite forming microorganism and cementation reagent into a soil matrix to form a cement compound which improves the engineering properties of soil. The natural soil was treated with 1.5x108, 3.0x108, 9.0x108, 18.0x108 and 27.0x108 of Bacillus megaterium suspension densities. The soil was classified as clayey sand (SC) according to USCS classification system and A-7-6(2) under the AASHTO classification system. The MDD increased by 0.56% while the OMC decreased by about 2.9% at 1.5x108 and 3.0x108 B. megaterium cell/ml respectively when compared with the natural soil. The cohesion was decrease by 53.97% while angle shearing resistance was increased by 36.99% at 3.0x108 B. megaterium suspension densities. This result shows a great improvement in the soil since the clayey nature of the natural soil was reduced.