Performance evaluation of a MICP-treated calcareous sandy foundation using shake table tests

摘要

Calcareous sandy foundations are susceptible to liquefaction when subjected to dynamic loading such as seismic or wave loading, which could cause severe damage to the superstructure and incur significant financial losses. Therefore, reducing the liquefaction potential of calcareous sand is of considerable significance. Microbially induced calcite precipitation (MICP) treatment is a relatively new method to improve the liquefaction resistance of calcareous sand, and it has the advantages of incurring small disturbances, low grouting pressure, less environmental harm, long transmission distance and a remarkable effect pertaining to the improvement of the engineering properties of the soil. However, few studies have evaluated the application of MICP treatment to calcareous sandy foundations. In this study, several shake table tests were conducted to evaluate the seismic performance of MICP-treated calcareous sandy foundations. Special attention was paid to the shear wave velocities, natural frequency and shear strength of the calcareous sand during MICP treatment. Additionally, the horizontal accelerations, pore water pressures and vertical settlements of calcareous sand before and after the treatment were compared. After MICP treatment, the shear wave velocity, natural frequency and shear strength of soil were improved, which indicated that the strength and stiffness of the model were considerably improved. During the shaking, the excess pore pressure ratio and surface settlement of MICP-treated model were significantly decreased. The liquefaction resistance of the MICP-treated model demonstrated greatly improved. However, the surface accelerations of the model strengthened by MICP were amplified. The test results indicate that use of the MICP method can significantly improve the strength, stiffness and liquefaction resistance of calcareous sand.