Hydro-mechanical coupling effect on water permeability of intensely weathered sandstone

The combined effect of stress and seepage is an important reason of engineering geological problems such as landslides, dam failures, and tunnel collapse. However, due to the limitations of the test apparatus, the existing studies rarely consider the stress effect in the seepage process. In this study, a soil column apparatus based on the wetting front advancing method was developed to explore the permeability properties of intensely weathered sandstone in a wide range of suction (10~106 kPa). The results suggest that the wetting front advancing velocity decreased as the vertical stress increased during infiltration, which indicates that the stress changes the infiltration channel and affects the infiltration rate. On the other hand, due to the water sensitivity of intensely weathered sandstone, the soil column deformation before and after wetting is significantly different, indicating that water infiltration further exacerbates the deformation. When vertical stress is applied to the soil column, the permeability coefficient-suction curves at different sections are paralleled in general, which is affected by the variation in dry density and the non-uniform distribution of stresses inside the soil column. Moreover, as the initial dry density increases, the influence of the vertical stress on the permeability coefficient gradually decreases. Key words: unsaturated soils, stress, permeability, hydro-mechanical coupling, wetting front
Introduction In mountainous areas with complex geological conditions, tunnel construction inevitably passes through extremely soft rocks, which are composed of soil formed by the weathering and decomposition of clastic rocks, [...]