Induced partial saturation for liquefaction mitigation by bio-gas bubbles nucleation

In order to increase the liquefaction resistance of a sand, the paper describes the experiments carried out by injecting non-pathogenic bacteria to generate gas bubbles as final product of their own metabolism. The produced gas is chemically inert, slightly soluble in water and of low environmental impact. A few lineages of denitrification bacteria, which are able to generate nitrogen gas bubbles through the reduction of nitrate, have been isolated in a sludge treatment plant. The tested soil is a silty sand retrieved from a site in Northern Italy where liquefaction evidences were observed during the 2012 earthquake. Laboratory tests were carried out at low stress states to quantify the amount of produced nitrogen gas, demonstrating that degree of saturation as low as 90% can be achieved.