Bio-stabilization of Sand by surface percolation

Most traditional soil improvement methods are time consuming, expensive, require heavy machinery and are environmentally detrimental. As a potentially more environmentally favorable ground improvement method, biomediated soil improvement offers an alternative to traditional soil improvement techniques. This method is based on microbial precipitation of calcium carbonate. The role of bacteria is producing urease enzyme to catalyzing hydrolysis of urea. In the presence of calcium ions, the produced carbonate ions in hydrolysis of urea, react with the calcium ions and calcium carbonate sediment was formed. This paper investigates the applicability of biomediated soil improvement in modification of dry loose sand by surface percolation. To evaluate the success of treatment, a series of laboratory experiments was conducted, including, shear wave velocity, unconfined compressive strength, Brazilian tensile strength, calcium carbonate content and etc. The study has revealed that biomediated improvement technique caused the improvement of strength as a result of the cementation of sand particles. Furthermore, surface percolation method has the potential of cementation and stabilization of loose sand with desirable depth. Increase in strength and calcium carbonate content decreases with increase of depth. Results also shows that increase of strength due to bio- improvement depends not only to calcium carbonate content but also to its spatial distribution in pores and particle-to-particle binding numbers.