高地应力条件下深埋洞室围岩损伤区孕育机制

EVOLUTION MECHANISM OF DAMAGE ZONE IN SURROUNDING ROCK MASS DURING EXCAVATION OF DEEP TUNNELS UNDER HIGH GEOSTRESS CONDITION

随着人类地下空间开发活动逐渐走向地球深部,高地应力已成为地下岩体工程典型的地质特征之一,并严重影响深埋洞室围岩的安全稳定。本文首先分析了我国地应力场分布规律,然后分别采用理论计算和数值模拟方法,研究了地应力准静态卸荷及瞬态卸荷条件下围岩损伤的产生机理与演化规律,最后结合加拿大URL地下实验室及锦屏二级水电站深埋引水隧洞围岩损伤检测结果,进一步探讨了高地应力条件下不同卸荷方式对围岩损伤区形成及特征的影响。研究结果表明:与地应力准静态卸荷相比,瞬态卸荷会在围岩中产生一个附加动应力,从而放大围岩径向卸载和环向加载效应,使得围岩更容易受损;随着侧压力系数的增大,瞬态卸荷和准静态卸荷诱发的围岩损伤范围均增大,并且在最小主应力方向上围岩损伤主要表现为剪切破坏,而在最大主应力方向上主要表现为拉破坏。

As the development activities of human underground space goes to deep earth, the high geostress has become one of the typical geological characteristics of underground rock mass engineering and has an important effect on the safety and stability of surrounding rock mass. In this paper, the distribution regularities of geostress field in our country are firstly analyzed. And then, the damage of surrounding rock mass induced by quasi-static unloading and transient unloading of geostress is studied by the methods of theoretical calculation and numerical simulation. At last, according to the testing results of damage in surrounding rock mass in Canada URL underground laboratory and diversion tunnels of Jinping II hydropower station, the influence of unloading way of geostress on the damage formation of surrounding rock mass is analyzed. Results show that comparing with quasi-static unloading of geostress, transient unloading of geostress can produce an extra dynamic stress in surrounding rock mass and enlarge the unloading effect in radial and loading effect in tangent, which makes the surrounding rock mass easier to damage. In addition, the increase of lateral pressure coefficient can increase the damage range of surrounding rock mass induced by quasi-static unloading and transient unloading of geostress augments. In the direction of minimum principal stress, the main damage form of surrounding rock mass is shear failure. While in the direction of maximum principal stress it shows as tension failure