滑带土长距离剪切强度及对滑坡启动的影响

滑带土的长距离剪切强度及其变化规律是滑坡启动的主要控制性因素之一，但是目前的常规直剪和三轴剪切试验还无法实现长距离剪切。为了研究滑带土的长距离剪切强度变化规律及对滑坡启动的影响，以四川省达县青宁乡滑坡为例，取其滑带土进行环剪试验，获得滑带土的长距离剪切强度变化规律，并与滑坡过程和运动特征进行对比分析。结果表明，滑带土长距离剪切强度变化规律与滑坡的启动过程较为吻合，滑坡首先受到降雨等因素触发开始变形和缓慢滑动，此时滑带土受到滑体的剪切，由于剪缩效应孔隙水压力迅速增大，导致剪切强度迅速减小，当小于某一临界值时，滑体开始加速并快速滑动。研究结论对类似的研究有一定的参考价值，可以为滑坡的预测预报和防治提供理论依据。 

Long-distance shear strength of slide-zone soil and its effect on landslide initiation

The long-distance shear strength of slide-zone soil and its variation law are the main controlling factors of landslide initiation. However, the existing common practice of direct shear test and triaxial shear test are unable to carry out the long-distance shearing. To study the variation law of long-distance shear strength of slide-zone soil and its effect on landslide initiation, a landslide in Qingning Township of Daxian County Sichuan Province was taken as an example to conduct a ring shear test on the slide-zone soil. The variation law of the long-distance shear strength of the slide-zone soil was worked out and analyzed in comparison with the process and movement characteristics of the landslide. The results showed that the variation of the long-distance shear strength corresponded with the landslide initiation process. The landslide was first triggered by the factors such as the rainfall, and then started to deform and slip at a low velocity. Under the shear stress of the slide mass, the pore water pressure increased sharply as a result of the shear shrinkage effect, which led to a sharp decrease of the shear strength. When the shear strength was below a certain critical value, the slide mass started to slip at a high velocity. The research conclusions can provide reference for other similar studies and theoretical basis for the forecast and prevention of landslide.