黄土-三趾马红土滑坡滑带土剪切力学特性影响因素

中国西北地区黄土广泛沉积于三趾马红土之上形成“双层异质”接触层面,控制和影响黄土滑坡的形成。为研究黄土-三趾马红土界面剪切力学特性,研制可视化界面直剪仪,开展界面试样剪切试验,探讨齿面角度、含水率、干密度对其剪切破坏模式、强度与变形特性影响规律。结果表明:试样均沿界面产生剪切破坏,试样剪切破坏模式可分为齿间滑动、齿间滑动-齿面剪断、齿面剪断3种; 界面试样剪切应力-位移曲线呈应变软化型,峰值强度后应变“跳跃”及“塑态”特征反映出界面的脆性与塑性剪断破坏特征,剪切刚度、剪切破坏位移演化规律均受界面接触条件影响; 界面剪切过程存在明显剪胀效应,剪胀位移演化规律反映了剪切过程的齿面挤密、齿间滑动、齿面剪断与界面摩擦阶段; 界面试样强度随界面接触条件均呈非线性变化,齿面角度越大,峰值强度与残余强度越高,试样剪切破坏模式越趋于脆性齿面剪断; 含水率越高,界面峰值强度越低,试样剪切破坏模式越趋于塑性齿面剪断; 界面试样干密度越大,峰值强度越大,残余强度越低,试样剪切破坏模式越趋于脆性的齿间滑动-齿面剪断。研究成果可为进一步研究黄土-三趾马红土界面强度准则,揭示黄土-三趾马红土复合型滑坡启动机制提供参考。

Influencing Factors on the Shear Strength of Sliding Zone of Loess-Hipparion Red Clay Landslide

Loess is widely deposited on Hipparion red clay forming weak interfaces, which controls the formation of loess landslide in Northwest China. In order to investigate the influ-ences of interface angle, moisture and density on shear failure mode, strength and deformation characteristics of interface samples, a series of shearing experiments were performed using a developed shear equipment. The results show that the shear plane of samples all generates along the contact interface, and the shear failure modes can be divided into sliding, sliding & shear-off, and shear-off; the shear stress-displacement curves are strain softening, and the shear stiffness and shear failure displacement are affected by the interface contact conditions; the “jumping” and “plastic” phenomena of post-peak strength reflect the brittle and plastic shear failure features of the interfaces; there is obvious dilation effect in the shear process, and the evolution of shear dilatancy displacement reflects the four stages of the shear process, including compaction of tooth surface, sliding along tooth surface, shear-off of tooth and interface friction; the shear strength of interface samples between loess and Hipparion red clay changes nonlinearly with the interface contact conditions; the peak strength and residual strength increase with the interface contact angle, and the failure mode tends to brittle shear-off; the peak strength decreases with the moisture, and the failure mode tends to plastic shear-off; the higher the density is, the higher the peak strength is, the lower the residual strength is, and the failure mode tends to brittle sliding and shear-off. The above results can provide references for studying the strength criterion of interfaces between loess and Hipparion red clay, and revealing the initiation mechanism of loess landslide.