liquefaction mitigation of medium-to-fine sands with microbial gas under cyclic triaxial loading

The microbial desaturation method is a new technique that is used to mitigate the liquefaction of sand. a series of strain-controlled cyclic triaxial tests was conducted to reveal that the microbial desaturation method is effective in improving the liquefaction resistance of saturation sand under cyclic loading. the test results showed that desaturated sand had a high liquefaction capability, and the increase rate of excess pore water pressure (epwp) was relatively slow. this is mainly due to the absorption of excess pore pressure by microbial gas in soil pores through volume reduction, which changes the bulk modulus and causes volume change of the pore modulus. the liquefaction resistance showed a considerable increase with decreasing saturation (sr). the values of the pore pressure ratio (ru) in the first cycle ranged from 0.63 to 0.025 when the saturation reduced from 100 to 84.1%. the number of loading cycles reaching liquefaction ranged from 7 to 92 when sr reduced from 100 to 84.1%. the stress path slope of sand containing microbial gas was close to 45. the dynamic shear modulus of sand increased with the reduction in sr, which had a strong consistency with the variation in ru. the dynamic properties of the sand were less affected by the relative density compared with the sr and the initial mean confining pressure. the liquefaction resistance of saturated sand was remarkably improved by increasing the effective confining pressure, decreasing saturation, and raising the relative density. the relationship between the peak average stress ratio (asrpeak) and maximum epwp ratio (ru,max) can satisfy the polynomial (asrpeak= aru,max2+ bru,max+c) well for sands with different sr. this can serve as the basis to evaluate the sand liquefaction strength for injecting the microbial bubbles into saturated sand on site