含陡缓倾结构面反倾岩坡折断面演化特征 的离心试验研究

Centrifugal test study of fracture evolution characteristics of anti-dip rock slope with steep and gently dipping structural plane

为研究含陡缓倾结构面的反倾岩坡在自重条件下的折断面演化特征,以苗尾水电站右坝肩倾倒变形体为地质原型,通过在坡体内不同部位预置切割岩层的非贯通裂缝开展离心模型试验,模拟反倾岩坡在自重条件下的折断面演化特征。研究表明:(1)含陡缓倾结构面的反倾岩坡破坏以折断面的形成为标志,折断面的形成分为3个阶段:初期(0~40g,g为重力加速度)为局部岩层断裂阶段,以岩层局部断裂及后缘岩层前倾为主要破坏特征,坡体表面位移变化量较小;中期(40g~80g)主折断面形成阶段,坡体深部结构面自上而下断裂扩展连接形成主折断面,坡体表面位移变化量约占总位移量的3/4;后期(80g~120g)为多级折断面形成阶段,以坡体内部断裂岩层应力重分布为主要变形特征,坡体表面位移基本保持不变。(2)结构面间岩桥断裂具有瞬时性,但折断面的形成是渐变发展的过程,主要受陡倾结构面控制,主折断面处裂缝应变量最大,受力方式最为复杂,次级折断面处裂缝应变量次之。(3)基于断裂力学,简化了复杂应力状态下含结构面的反倾岩坡压剪断裂判据和岩层不平衡力公式,揭示了主折断面处岩层不平衡力呈现由坡体高度1/3处向坡底和坡顶两侧变小的规律,折断面的形成主要受剪应力与正应力的强度因子比值、岩层结构面长度和裂纹率共同影响。

In order to study the evolution characteristics of the fracture plane of the anti-dip rock slope with the steep and gently dipping structural plane under the condition of its own weight.Taking the toppling deformation form of right abutment of Miaowei Hydropower Station as the geological prototype,the centrifugal model test was carried out by presetting non-penetrating cracks of the rock strata in different parts of the slope body to simulate the evolution characteristics of the fracture surface of the anti-dip rock slope under the condition of its own weight.The researches have demonstrated that:(1)The failure of anti-dip rock slopes with steep and gently dipping structural planes are marked by the formation of fracture surfaces,which are divided into three stages:in the initial period(0–40g,g is the acceleration of gravity),it refers to the stage of partial fracturation which takes partial fracturation and stratum forwarding on the trailing edge as the major failure characteristics with less position changes in slope plane.In the middle period(40g–80g),it refers to the formation stage of major fracture plane which can be formed in the deep structural plane of slope through expansion and connection in a top-down approach.Position changes in slope nearly account for 3/4 of total position changes.In the later period(80g–120g),it refers to the formation stage of multi-stage fracture plane whose main formation feature is the stress redistribution of fracture strata within the slope.Position changes in slope basically remain unchanged.(2)The fracture of rock bridge between structural planes is transient,but the formation of fracture plane is a gradual development process which is mainly controlled by steep-inclined structural planes.The strain at the crevice of the main fracture plane is the greatest and the stress mode is the most complex.And the fracture strain at the secondary fracture plane takes the second place.Based on fracture mechanics,the fracture criteria of the rock compression-shear and unbalanced force formula for rock stratum have been simplified.It is revealed that the unbalanced force of the rock stratum at the main fracture surface decreases from 1/3 of the slope height to the bottom and top of the slope.The formation of fracture surface is mainly affected by the ratio of the intensity factor of shear stress to normal stress,the length of rock structure plane and the crack rate.