Yield-stress evolution of cement-stabilised soil under constant and variable curing-stress paths

Yield stress is important for evaluating the compression behaviour of cement-stabilised soil in deep mixing, jet grouting and ground improvement with preloading. Previous studies have shown that constant curing stress can increase yield stress, but whether this increase is mainly associated with the reduction in after-curing void ratio remains unclear. In practice, curing stress develops progressively during construction, while yield-stress evolution under variable curing stress remains insufficiently understood. This study used one-dimensional compression tests to investigate yield-stress evolution under constant and variable curing stresses. Under 7 days of curing, increasing constant curing stress from 0 to 12.5 kPa raised yield stress from 80.2 kPa to 195.8 kPa, with a non-linear increase corresponding to the reduction in after-curing void ratio. At the same curing time, samples with and without constant curing stress exhibited nearly the same yield stress at close after-curing void ratios, indicating that the increase under constant curing stress was mainly associated with void-ratio reduction. At matched curing times and after-curing void ratios, samples under the variable curing-stress path showed yield stresses 1.6–3.9 times those under constant curing stress and lower compressibility. These results show that the stress path during curing should be considered in the analysis of yield behaviour.