THE STRENGTH AND POROSITY PROPERTIES OF MICP-TREATED AEOLIAN SANDY SOIL

The aeolian sandy soil is widely distributed in the desert zone. It is vulnerable to the wind erosion and serves as the dust source of the sandstorm due to its fine particles and the non-cohesion property between particles. The microbial induced calcite precipitation (MICP) is one of the bio-geotechnical technology. This paper examines the MICP-treated aeolian sandy soil through a self-designed preparation method and process. The strength properties and their influence factors, the concentration of the bacterium, the porosity and grain distributions, are discussed. Testing results indicate that the suitable curing time for obtaining enough strength with good efficiency is 7 d for the MICP-treated sandy soil samples in this study. It is found that the MICPtreated aeolian sandy soil can have an average unconfined compress strength of 0.66MPa and an average inner friction angle of 36ffi in this reasonable range of OD600 0.5~0.8. The feasibility of the MICP-treated aeolian sandy soil is verified in the application of bio-crusts in desert engineering. The pore space and the porosity of the soil matrix play an important role in the MICP process. When the soil matrix with high porosity is well-graded, the MICP-treated sandy soil samples may have a high strength. Furthermore, the pore features are tested through the nuclear magnetic resonance (NMR) technology before and after the mineralization. The results indicate that the pores are well developed after the mineralization. The radius of most pores is in the range of 30 μm to 50 μm, and the pore with radius of 100 μm offers most of pore volume. The porosity is decreased by about 15% after the mineralization as compared with the unmineralized for the same sample.