Microbial soil desaturation for the mitigation of earthquake liquefaction

Soil liquefaction is a common geo-hazard in active earthquake zones. Regular measures against soil liquefaction such as soil densification and soil cementation only have limited scope of applications because of their high costs and complicated implementations. An alternative approach to the mitigation of soil liquefaction is desaturation, that is, to lower the degree of saturation of originally saturated soil. However, the key challenge is to develop a reliable technique to achieve desaturation effect in liquefiable soil ground in a uniform manner. In this paper, an innovative technique, microbial soil desaturation, is introduced and evaluated. Denitrifying bacteria are adopted to produce tiny gas bubbles in-situ from nutrients. The nutrients are dissolved in water and thus can flow like water in sand. The performance of the technique is evaluated using shaking table model tests. It is found that when the degree of saturation of the specimens has decreased from 100% to 90%, the excess pore water pressure generation and the liquefaction potential of sand under seismic loading can be greatly reduced.