降雨型红层滑坡形成机理研究

以贵州省习水县某红层滑坡为例，在野外详细调查基础上，结合室内力学试验、数值模拟技术，查明该滑坡变形破坏特征，得出节理裂隙、水对泥岩力学强度的影响效应，综合分析并阐明滑坡形成机理.研究表明：该滑坡属于典型的降雨顺层滑坡，滑坡的形成是由降雨、地形、开挖以及岩土体性质综合所致.开挖为滑坡的剪出提供临空面，降雨过程中坡体渗流场显著变化，在强/中风化层界面逐渐形成连续饱和带，开挖所引起的渗流路径改变最终反映在开挖断面附近形成较大的饱和区.各监测点孔隙水压力均呈现出持续增长趋势，随着高程增大，孔隙水压力变幅逐渐减弱.节理裂隙的发育使泥岩强度弱化，遇水后节理裂隙、水的综合作用使泥岩强度发生极大衰减，内聚力降低82%，内摩擦角降低57.9%，内聚力受影响程度高于内摩擦角，进而影响坡体稳定性，在自重势能下沿层面向开挖临空方向滑动剪出，最终造成剪出口前部房屋严重损毁.

FORMATION MECHANISM OF RAINFALL-INDUCED REDBED LANDSLIDE

Taking the redbed landslide in Xishui County of Guizhou Province as an example, on the basis of detailed field survey, combined with laboratory mechanical tests and numerical simulation technology, the paper finds out the deformation failure characteristics of landslide and effect of joint fissures and water on the mechanical strength of mudstone, and analyzes the formation mechanism. The results indicate that the landslide is of typical rainfall bedded type caused by the combination of rainfall, terrain, excavation and rock-soil property. Excavation provides free face for shearing of landslide. While the seepage field of slope body changes significantly during rainfall, continuous saturated zone is gradually formed at the interface of strongly and moderately weathered layers, and the change of seepage path caused by excavation results in the formation of large saturated area near the excavated section. The pore water pressure at all monitoring points shows a continuous increasing trend, and its pressure range decreases gradually with the increase of elevation. The development of joint fissures weakens the strength of mudstone. The joint fissures activated by water greatly attenuate the strength of mudstone, with the cohesion decreasing by 82% and internal friction angle by 57.9%. The former is affected more than the latter, and then the slope stability is affected, sliding and shearing along the surface towards excavation direction under the self-weight potential energy, eventually causing severe damage to the houses in front of shear outlet.