The distribution of pore water pressure in a stratified soft rock slope with hydraulic conductivity anisotropy

Poorly cemented and stratified sandstone, mudstone and shale are the main formations in the hill distributed in northern and central regions of western Taiwan. Slope failures following by heavy rainstorm are common in these areas. For this reason, the research aims to study the effect of hydraulic-conductivity anisotropy on pore water pressure (PWP) distributed in these soft rock slopes through numerical simulation. It is shown that the PWP distribution of finite slope with hydraulic anisotropy is extremely different from the one of isotropic slope. For a stratified soft rock slope, estimating the PWP using a phreatic surface with isotropic and hydrostatic assumptions will strongly mislead the results. Numerical experiments show that the PWP distribution significantly depends on the ratio of hydraulic conductivity anisotropy and dip angle of strata. It is strongly recommended that a flow analysis taken hydraulic anisotropy into consideration is required prior to performing the slope stability of a stratified soft rock slope.