垂直向地震作用对节理岩体失稳破坏的影响

Influence of Vertical Seismic Action on Seismic Dynamic Failure of Jointed Rock Mass

基于线弹性断裂力学理论分析了垂直向地震作用对节理岩体地震动力破坏的影响。在仅考虑峰值时,最不利的单向地震动加速度方向是水平倾向坡外,双向则依据破裂机制是拉剪或压剪,加速度分别是水平倾向坡外与向下或向上的组合。地震动的幅值、作用方向及双向地震动的组合都可使岩体的破坏机制发生转化,并且是突变的、不可逆的。较低峰值的双向地震动产生的应力强度因子可能大于较高峰值的单向地震动所产生的应力强度应子。在岩体节理分布特征和静态应力场一定的初始条件下,第一个导致岩体中产生破裂的地震动加速度幅值及其方向的组合唯一地决定了岩体不可逆破坏发展的方向、机制及最终的破坏特征,其复杂性远大于静力作用时的情况。对岩体地震动力破坏问题的认识应充分考虑垂直向地震动的重要影响。

Based on the theory of linear-elastic fracture mechanics, the influence of vertical seismic action on seismic dynamic failure of jointed rock mass is discussed. When a single peak acceleration loads on rock mass, the severest accelerated direction is horizontal slip-outward, and for acceleration with two directions, the severest ground motions are the combination of horizontal slip-outward with upward or downward according to that its failure mechanism is tenso-shear or com- presso-shear crach. The amplitude, direction and combination of horizontal and vertical accelera- tions can change the failure mechanism of rock mass and the changing is catastrophic and irreversible. The dynamic stress factor from two lower accelerations of horizontal and vertical might cause more serious failure than that from higher single acceleration. For given jointed rock mass and static stress field, the amplitude and direction combination of first ground motion accelera- tions causing failure in rock mass will determine the unique development direction, mechanism and final characteristics of rock mass failure, therefore, the seismic dynamic failure of rock mass is much more complex than static failure. The influence of vertical seismic action on seismic dynamic failure of jointed rock mass should be considered comprehensively.