Time-dependent calculation method of pore pressure for non-uniform lifting in tunnel waterproof grouting and its engineering application

To address the potential issue of uneven rehabilitation effectiveness and the consequent insufficient durability of the grouting ring caused by the homogeneous medium assumption in traditional tunnel water-stop grouting methods, this paper proposes a pore pressure time-varying calculation method capable of describing non-uniform uplift effects. Based on elastoplastic damage theory, a damage variable characterizing material degradation is introduced to accurately represent the cumulative damage phenomenon in the lining under long-term cyclic loading. Considering both non-uniform damage and the time-varying characteristics of soil pore water pressure, an equivalent pore pressure model is incorporated. Through fluid-solid coupling calculations, the control mechanisms of grouting parameters on the evolution of the pore pressure field are systematically analyzed. The research results effectively address the issues of non-uniform damage and leakage in metro tunnel linings within water-rich soft-hard composite strata under long-term dynamic loads. Data indicate that grouting pressure is the dominant factor controlling uplift magnitude, with the maximum uplift increasing by 65%–80% when the pressure rises from 1.0 MPa to 2.0 MPa. The grouting range primarily governs uplift uniformity, and under optimal conditions, the differential uplift can be controlled within 1.5 mm. This study elucidates a grouting design method based on precise damage assessment, providing a theoretical foundation for the "targeted treatment" and parameter optimization in tunnel rehabilitation.