Gas permeability of intact loess under traixial stress conditions

The gas permeability tests on intact loess with various water contents are performed under traixial stress conditions using the refitted triaxial gas permeability equipment. Influences of changes in the mean stress, deviator stress and water content on gas permeability as a function of liquid saturation are analyzed. The gas permeability function considering their effects is proposed. The results show that the relationships between gas permeability and liquid saturation are affected clearly by the deviator stress and mean stress as well as water content. The gas permeability decreases linearly with the increase of liquid saturation resulted from the mean stress with constant stress ratio or deviator stress with constant mean stress, and the decreasing degree is dependent on the value of water content. The decreasing rate of gas permeability with the increase of liquid saturation is smaller during the increasing water content than that during increasing stress. There are all unique relationships between the relative gas permeability and the liquid saturation between the gas permeability and the modified gas saturation at different stress states. These relationships can be predicted by the P-vG-M model in term of the total liquid saturation and proposed modified gas saturation power law (MAPL) model, respectively. In comparison with the P-vG-M model, the MAPL model with less parameters is more convenient for engineering application. The predicted results of gas permeability by MAPL model are in good agreement with the test ones.