中部“砥柱”锁固平面旋转切向层状岩质滑坡启动力学机理与稳定性判据

中部“砥柱”锁固平面旋转滑坡,是切向层状岩质斜坡在特殊的边界条件控制下,发生渐进性变形而形成的。其主要特征是：在平面上,滑体中部的潜在滑床面部位,岩层抗剪强度较高,出现坡体变形的相对锁固段：而由滑体中部向周围边界,坡体变形逐渐增大。且变形岩体围绕着滑体的中部呈现出平面旋转变形之趋势。引起滑坡平面旋转的根本原因是滑体在变形时,其所受诸力的合力不通过滑体重心,从而产生了使滑体发生旋转的力矩。其变形与破坏模式可以概化为：在自重力、滑床摩擦力、滑床锁固段阻力和滑体周围边界处围岩切层阻力的共同作用下,圆环状岩块(岩板)所发生的平面旋转变形以及临界状态下“锁固段”的旋转破坏问题。基于弹性力学的平面应力问题,分析了圆环状岩块的旋转应力场：并应用极限平衡方法,分析了旋转滑坡下滑失稳的启动条件和旋转滑动的力学机理,建立了滑坡稳定性的判据。

DYNAMICS AND STABILITY CRITERION OF OBLIQUE LAYERED LANDSLIDE WITH PLANE ROTATION UNDER LOCKUP OF CENTRIC SEGMENT

Landslide with plane rotation under lockup of centric segment is formed in the course of progressive failure of layered rocks on the oblique bank slope. It is characterized that there exists a relative locked segment on bedding plane around the center of a landslide body with bigger shear strength and torsion sliding impeded,whereas the movement of slope increases gradually from the center to the outer segment in which the layered rock mass spins around a hinge located in the center on potential bedding plane. The reason why landslide exhibits plane rotating is that resultant of forces acting on the landslide body does not traverse its center of gravity,which results in a moment of rotation. So the deformation and failure mode of landslide can be described by rotation of a circled rock slab with inner fixed part under combined loading of gravity,friction forces on potential bedding plane,shear strength in centric part,and resistance to rotating on boundary. By means of elasticity theory,the rotation stress field of the circled layered rocks is deduced. Furthermore,the triggering condition of rotating glide is studied and onset mechanism and stability criterion of landslide are established with the approach of limit equilibrium. The study result is proved to be effective in the quantitative evaluation of stability of this kind of landslide.