Effects of Cement Ratio and Curing Period on Interface Shear Strength of Cement-Treated Soil

Shear and interface shear strength are crucial parameters in designing soil–cement mixture and the retaining wall in the soil modified by the deep cement mixing method. In this study, the effects of varied cement ratios and curing period on the shear and interface shear behaviors of cemented soil were investigated using modified direct shear tests. The result showed that the shear strength of the soil–cement mixture increased with curing time. Additionally, at 28 days, increasing the cement ratio to 10% significantly improved the shear strength and interface shear strength of the cemented soil, up to 2.5 and 1.7 times, respectively. Similarly, the internal friction angle increased twice for both cases, while the cohesion in the case of shear strength decreased slightly. Additionally, the friction coefficient between the soil–cement mixture and the plate steel increased as the cement ratio increased. Finally, empirical equations were derived to estimate the shear and interface shear strengths at 28 days based on the cement ratio and normal pressures.