斜坡发育过程中的σ_3效应

σ3-EFFECT OF LEAST PRINCIPAL STRESS IN THE SLOPE DEVELOPING PROCESSES

斜坡发育过程中,正倾岩层的屈曲变形和水平岩层的塑性流动,受坡体内存在的最小主应力σ_3梯度作用而成。σ_3效应主要呈现有:屈曲滑坡和挤出型块体滑坡。

σ3-effect is mainly expresed as two kinds of landslide phenomena.1.Buckling landslide in anaclinal bedded rocksThe test results of the long strip test piece in rigid channel shows that there exists the second principal stress σ2 along the channel walls of both sides .which are opposite in direction and equal in effects to limit the lateral expansion of test samples due to axial stress σ1; the least principal stress σ3 would be formed while the channel bottom is upward,and it would push up the samples to occur deflection and bending-moment while the axial stress σ1 deviates the axis of the test samples.and a upward yield-bending phenomenon will be formed.The field investigation results;on the long slope,while the dip angle of the thin and anaclinal bedded rocks equals or approximates to the slope angle of the slope surf ace, and the dipping direc-tion of bedded rock equsls basically to the slope direction, there occur yield-bending deformation and even buckling landslide at the foot of the slope because oveffects exists.2.Crushing landslide in the horizontal bedded rocksOn the border of the slope,the differential unit rock and earth bodies(clay or soft rock)could expande freely to outside, which is freeing, while it is pressured uniformly by the gravity from the upper hard rocks of the slope, e. i. σ3 = 0. There exists the lateral stress while the expansion is limits at the internal side.e. i. σ3≠0.Thus,a stress difference ( stress gradient) forms between the two sides of the unit rock and earth bodies. Under the action of the stress gradient, the unit rock and earth bodies are slowly crushed to outside and the upper hard rocks,as a mass,creep with the unit rock and earth bodies to form crushing landslide.