Desaturation for Liquefaction Mitigation Using Biogas Produced by Pseudomonas stutzeri

The shear strength of sand increases with decreasing degree of saturation. This study attempts to develop a more effective biogas desaturation method to mitigate liquefaction of sand. The microbial denitrification process of Pseudomonas stutzeri, which produces nitrogen gas, was selected for inducing partially saturated sand. First, research was undertaken to verify the denitrification performance to demonstrate the feasibility of utilizing P. stutzeri. Compared to existing methods using biogas, the reducing time of nitrate and nitrite was less in the proposed denitrifying cultivation. Then, a control method for desaturation was proposed by gas generation tests. To explore the effect of mitigation liquefaction using this method, fully and partially saturated sand specimens were prepared and shaking table simulation tests were performed under a series of cyclic loadings with different acceleration amplitudes. The influence of the initial degree of saturation on excess pore water pressure, pore water pressure ratio, and surface settlement was investigated. Finally, the exponential relationship between volumetric strain and average pore water pressure ratio was established for fully and partially saturated sand specimens.