Coupling effect of macro- and micro-properties of cement-modified clay and assessment of slope stability under rainfall infiltration

This research systematically examines how cement content and curing duration affect the mechanical behavior, microstructural evolution, and rainfall-induced slope stability of Qinghai Plateau clay, using UU triaxial and variable-head permeability tests, NMR, XRD, and ABAQUS simulations. The results demonstrated that with increasing cement content and curing duration, peak stress and strength increase significantly. under the condition of 16 % cement content and 28 d curing duration, the strength improvement of the cement-modified clay is the most evident. For 16 % cement content, as the curing duration increases from 0 d to 28 d, cohesion and internal friction angle increase from 16.051 kPa and 31.087° to 37.602 kPa and 65.592°, respectively, and the permeability coefficient decreases from 8.1 × 10⁻⁶ to 7.3 × 10⁻⁶ cm/s; NMR shows at a curing age of 28 d, when the cement content increases from 0 % to 16 %, total porosity decreases from 38.3 % to 33.2 %, for 16 % cement content, as the curing duration increases from 0 d to 28 d, total porosity decreases from 36.1 % to 34.8 %; XRD confirms the formation of calcium silicate hydrate (C–S–H) gel and calcite, and the consumption and transformation of ettringite and other clay mineral phases; Numerical simulations (rainfall intensities of 50, 100, and 200 mm/d) indicate that, compared with the clay slope, the cement-modified clay slope accumulates shallow pore-water pressure more rapidly; however, the overall settlement and the extent of the plastic zone are significantly constrained, and the factor of safety decreases from 1.76 to 1.41, yet remains within the acceptable design threshold.