温度对边坡夹层力学性能的影响及破坏机理

为研究温度对边坡夹层力学参数的影响,以膨润土和河砂为相似材料,配制了7种不同配合比的夹层试样,采用改装了加热升温控制系统的应变直剪仪,测试含水率为10%,13%,15%的夹层试样在不同温度时的抗剪强度指标等力学参数,分析其受温度和含水率影响的变化特征及其破坏机理。研究结果表明:在温度相同时,夹层试样的黏聚力和抗剪强度随膨润土含量的减少而减小;膨润土含量较高的夹层试样,其黏聚力和抗剪强度随温度升高呈现出先急剧减小、而后缓慢减小、最后再急剧减小的变化规律,且其关系曲线随含水率的升高而逐渐趋于平缓,最后呈线性下降趋势;温度升高时,夹层试样水合力降低,引起其内部土颗粒之间的微观结构力弱化,导致其黏聚力急剧减小;当温度升高至50 ℃以上时,夹层试样内部土颗粒之间克服微观结构力而产生滑移,导致其黏聚力再次急剧减小,此时夹层试样进入临界破坏状态。因此,黏聚力是影响夹层试样破坏状态的关键因素,可将黏聚力再次急剧减小的起始点视为夹层试样破坏的关键点及其评价指标。

Effect of Temperature on Mechanical Behaviors of Interlayer in Slope and Failure Mechanism

The effect of temperature on the mechanical behaviors of slope interlayer was investigated on direct shear test device with temperature control heating system. Seven interlayer specimens with different mix proportions of bentonite and river sand at varied moisture content (10%, 13%, 15%) were prepared for the test. The shear strength indexes of slope interlayer specimens at different temperatures were measured to further examine the failure mechanism. Results demonstrated that at a given temperature, cohesion and shear strength of interlayer specimens decreased with the shrinking of bentonite content; while with the climbing of temperature, specimens of high bentonite content experienced dramatic decline, gentle decline, and then finally dramatic decline again in terms of cohesion and shear strength. Moreover, such relation curve tended to be gentle and finally displayed a linear decline with the rising of moisture content. As temperature decreased, the resultant force of water in slope interlayer decreased correspondingly, which weakened the microstructural force among soil particles, resulting in a sharp reduction of cohesion; when temperature exceeded 50 ℃, cohesion decreased dramatically again because of slip of soil particles, giving rise to a critical failure state. Therefore, cohesion is a key factor inducing the failure of interlayer specimen, and the critical point of cohesion reducing dramatically again could be regarded as the indicator of the failure of slope interlayer.