饱和度对风化花岗岩边坡土体抗剪特性的影响

Effect of saturation on shear strength characteristics of weathered granite slope soils

强降雨易诱发风化花岗岩边坡浅层滑坡,其滑坡滑动面多位于具有较大孔隙尺寸的强风化带。通过对广西玉林与梧州交界处风化花岗岩边坡浅层滑坡的现场勘查和对不同层位的土体进行物理力学试验,研究了饱和度对湿热地区风化花岗岩双层土质边坡抗剪强度的影响,发现两个风化带土体都存在一个"最优饱和度"使抗剪强度达到峰值,但饱和度对抗剪强度指标的影响规律不同,即饱和度对黏聚力影响很大,对内摩擦角影响很小;花岗岩全风化带与强风化带土体性质差异明显,尤其表现在饱和度影响下抗剪强度特性方面,从基质吸力理论和颗粒间胶结作用角度分析所发现的现象,可以清楚地解释产生差异的机制,为风化花岗岩边坡的开挖和滑坡的防治提供理论基础。

The shallow landslides are often triggered by heavy rainfall in weathered granite soil slopes. These slope failures usually occur in a strongly weathered granite layer which has a big pore size. These can cause great casualties and property losses. Through field investigation and laboratory experiments, the effect of saturation on the shear strength of highly weathered soils and completelyweathered granite soils taking from the intersection of Yulin and Wuzhou are investigated. It is found that there exists an 'optimal saturation' at which the shear strength of the soil reaches the maximum. The influence of saturation on both cohesion and internal friction angle does not show a unique trend. It is also shown that the cohesion is significantly effect by the saturation of the soils; but the friction angle is not. Completely weathered granite soils and the highly weathered granite soils are significantly different in their lithological, composition, construction and shear properties. The characters of the highly weathered soil and completely weathered granite soil are significantly different, especially in the relationship between saturation and shear strength.Based on the analysis of cementation effect and the principles of matric suction, a sound explanation for the mechanisms underlying the above-observed discrepancy is provided.