干湿效应下崩岗区岩土抗剪强度衰减非线性分析

发育于花岗岩的崩岗侵蚀区红土受干湿变化影响显著。通过室内直剪试验,研究了不同干湿效应对崩岗侵蚀区岩土抗剪强度衰减的影响。试验处理采用5种干湿效应水平(风干48h、风干24h、自然含水率、浸30s和浸60s)。结果显示:土壤黏聚力c和内摩擦角φ随干湿变化呈非线性衰减趋势,当土壤含水率13%左右时,对应的抗剪强度指标出现峰值;峰值强度前符合线性递增规律,峰值强度后符合一阶指数衰减规律。在风干阶段,抗剪强度主要受裂隙性影响,而在增湿阶段,基质吸力是影响抗剪强度的主要因素;探讨了干湿循环效应对崩岗侵蚀发育的影响。

Effects of drying and wetting on nonlinear decay of soil shear strength in slope disintegration erosion area

Red soils derived from granite in slope disintegration areas are influenced significantly by wetting and drying. Effects of wetting and drying changes on decay of soil shear strength in slope disintegration areas were investigated in laboratory by direct shearing test. Five soil wetting and drying treatments (drying 48 h, drying 24 h, natural water content, wetting 30 s, wetting 60 s) were tested. Experimental data indicated that shear strength indices (soil cohesive force and internal frictional angle) declined with drying and wetting levels, and they reached to the maximum at the water content of about 13%. The relationship between shear strength indices and drying and wetting levels could be simulated to linear function before strength peak and to first order exponential decay function after the peak; Shear strength was dominantly affected by crack evolution during drying period, while matric suction was the main factor for shear strength decline. Finally, the drying and wetting effect on development of slope disintegration was discussed in the paper.