Multifield Coupling Mechanisms and Support Strategy for Creep–Seepage Interaction in Water‐Bearing Argillaceous Soft Rock Tunnels

Water‐bearing argillaceous soft rock, characterized by high porosity, low bearing capacity, and water sensitivity, is prone to instability under creep–seepage coupling effects in tunnel engineering, threatening construction safety. This study investigates the soft rock of a water conveyance tunnel in Henan Province, China. Through triaxial creep‐seepage coupling tests and microstructural analysis, the influences of confining pressure, axial pressure, and time on creep characteristics and permeability evolution were systematically investigated. Results indicate that a 0.1 MPa increase in confining pressure raises the peak strength by 12.09% and reduces creep deformation by 88.06%. Permeability decreases nonlinearly with increasing axial pressure (e.g., a decrease of 1.28 × 10 −15 m 2 was observed when axial pressure increased to 0.4 MPa under 0.1 MPa confining pressure). High confining pressure significantly diminishes the effect of axial pressure on permeability (reducing its influence to 28.9% of that under low confining pressure). Microstructural observations revealed that confining pressure enhances compactness by compressing pores and closing microcracks, while creep–seepage coupling induces dynamic closure of pore channels. Based on these findings, a composite support system of “inverted steel arch + rock bolts + shotcrete” was proposed. Field applications showed that this system effectively controlled the maximum surrounding rock deformation to within 292 mm, with deformation rates stabilizing within 20 days. This study provides theoretical and technical support for stability control in water‐bearing argillaceous soft rock tunnels.