Desaturation via biogenic gas formation as a ground improvement technique

Desaturation by biogenic gas formation can significantly affect the hydro-mechanical behaviour of soil. The high compressibility of the gas dampens pore pressure build up during both monotonic and cyclic undrained loading. Stimulating biogenic gas production therefore has potential as a ground improvement method to mitigate the risk of both static liquefaction and earthquake induced liquefaction. However, gas generated below the ground water table at shallow depth may also constitute a hazard for offshore foundations and terrestrial deposits, as a sudden release of trapped gas may cause instability. In order to evaluate the potential use of biogenic gas for geotechnical applications it is essential to be able to predict gas production and assess its effect on the hydro-mechanical behaviour of a soil. A basic theoretical framework to estimate the volume of gas produced by a biogenic process and the related degree of saturation, experimental results on the rate of gas generation, and its impact on soil behavior are presented herein.