Remediation of liquefaction potential of sand using the biogas method

Liquefaction of sand can cause catastrophic slope failure, especially in non-cohesion materials such as sands and tailings. One method for the mitigation of liquefaction risks of sand is desaturation - to make the saturated sand slightly unsaturated. Several potential techniques for reducing the degree of saturation have been explored. One is to use microorganisms to generate biogas in soils. Microbial denitrification process is a way to serve this purpose. By using this method, nitrogen (N2) gas can be produced by denitrifying bacteria in-situ in the zone to be treated. A 1-g shaking table laminar box was designed and used to investigate the liquefaction behavior of both saturated and desaturated sand. Saturated sands at loose state under amax=0.5 m/s2 and at medium dense state under amax=1.5 m/s2 show complete liquefaction manner by exhibiting violent volumetric strains and pore water pressure ratios close to unit. By lowering the degree of saturation from full saturation to about 90%, volumetric strain and pore pressure generation can be reduced by several times at the same condition. The difference in the bearing capacity of sands can also been seen. It can be concluded from the study that the liquefaction susceptibility in sand can be greatly reduced by the biogas method. This method may also be more cost-effective than any other conventional methods such as densification and chemical modification.