花岗岩残积土持水特性及强度特性研究

Study on the Water Retention and Strength Characteristics of Granite Residual Soil

摘要: 为探究花岗岩残积土的持水特性及抗剪强度随含水率的变化规律，以重塑花岗岩残积土为研究对象，采用滤纸法测定其土水特征曲线(SWCC)，并通过直剪试验研究不同含水率条件下土体的抗剪强度特性。试验结果表明：花岗岩残积土的SWCC呈典型反“S”型，基质吸力由100 kPa升至3000 kPa时，体积含水率由40.0%降至25.0%，表现出较强的持水能力和明显的阶段性脱水特征；随着含水率从16.15%增加至23.93%，土体的黏聚力由15.8 kPa降至10.15 kPa，内摩擦角由34.2˚减小至28.3˚，抗剪强度显著下降；剪切曲线形态由应变软化型逐渐过渡为应变硬化型，反映出土体由脆性破坏向塑性破坏的转变。研究表明，含水率是影响花岗岩残积土抗剪强度的关键因素，研究成果可为非饱和土边坡稳定性分析提供理论依据。

Abstract: To investigate the water retention characteristics and the variation in shear strength with moisture content of granite residual soil, remolded granite residual soil was used as the research subject. The soil-water characteristic curve (SWCC) was measured using the filter paper method, and the shear strength behavior of the soil under different moisture contents was studied through direct shear tests. The test results indicate that the SWCC of granite residual soil exhibits a typical inverse “S” shape. When the matrix suction increases from 100 kPa to 3000 kPa, the volumetric water content decreases from 40.0% to 25.0%, demonstrating strong water retention capacity and distinct staged dehydration characteristics. As the moisture content increases from 16.15% to 23.93%, the cohesion of the soil decreases from 15.8 kPa to 10.15 kPa, and the internal friction angle decreases from 34.2˚ to 28.3˚, indicating a significant reduction in shear strength. The shear stress-displacement curve transitions from strain-softening to strain-hardening behavior, reflecting a shift in the soil failure mode from brittle to plastic. The study shows that moisture content is a key factor affecting the shear strength of granite residual soil. These findings provide a theoretical basis for the stability analysis of unsaturated soil slopes.