Compressibility Behavior of MICP-Treated Sand Treated under Unsaturated Conditions

Microbially induced calcium carbonate precipitation (MICP) is a soil improvement technique that has the potential to meet the expanding needs of society with marginal environmental consequences. In this method, biological activities of bacteria lead to formation of calcium carbonate at particle–particle contacts. Precipitated cementation links soil grains together and improves engineering behavior of soil. In recent years, the method has demonstrated promising results in a wide range of geotechnical applications where soil stabilization is mainly performed under unsaturated conditions. However, the deformation and compressibility behavior of unsaturated MICP-treated soil is yet to be investigated. A series of consolidation tests were performed on untreated and MICP-treated sand specimens. Specimens were treated by percolation in unsaturated conditions. Tests were performed in a modified consolidation setup equipped with bender element sensors. Consolidation test results indicated that unsaturated MICP-treatment significantly reduced compressibility of soils. A sudden collapse in shear wave velocity measurements with stress increment was observed in moderately cemented specimens that was less pronounced in lightly and heavily cemented specimens.