Shallow biogenetic gassy sand soil is one of special unsaturated soil. The biogenetic gas with different quantities constained in the sand soil has great influence on its engineering properties. In this paper
the preliminary judgment is drawn on the existence of the biogenetic gas in the fluvial-lacustrine deposit sand soil
and then the in-situ and laboratory tests are done to compare the bearing capacities of the soil before and after gas release. It is found that without seepage failure
the slow release of the biogenetic gas can increase the bearing capacity of the soil
which is benefit to the stability of the upper buildings.