高应力深部洞室模型试验分区破裂现象机制的初步研究

Mechanism analysis of phenomenon of zonal disintegration in deep tunnel model test under high geostress

以经典的芬纳公式为手段,以观察到分区破裂现象的模型试验为背景,通过对简化后的圆形巷道围岩应变场和能量场的分析,发现极限平衡区边界存在径向应变的不连续性和弹性变形能的聚集性。认为与开挖洞室呈同心圆的环状断裂的形成,是极限平衡区在边界上由于应变场的不协调而导致的与弹性区的断裂分离。而分区破裂的产生,则是这种断裂分离形成后极限平衡区向深处发展的结果。解释了分区破裂产生时洞周围岩应变和位移随距离洞室增加呈波浪形变化的非单调性规律,给出了分区破裂形成后各破裂区半径的表达式,关系式表明各破裂区之间存在等比关系,比值与地应力状态及围岩力学参数有关。将分区破裂模型试验的参数代入该式,可得,n=1.1左右,与实验完成后剖开模型的各破裂区分布特征基本相符。

At the background of zonal disintegration was found in the model test, the strain field of the circular tunnel was studied by using the classical Fenner formula. The discontinuity of the radial strain and the concentration of elastic deformation energy were found at the ultimate balance boundary. The formation of the circular crack which is concentric to the opening is the rupture and separation between the ultimate balance zone and the elastic zone caused by the discontinuity of the strain field. Zonal disintegration is the result of ultimate balance zone expanding to deeper rock mass after the separation. The analysis results explain the non-monotonic under changing laws of the strain and displacement in surrounding rock mass with the distance to the cavity increasing; and the formula of radius of the fractured zones was got and it showed that there exist the equal ratio relations between the radiuses. The value of it was corresponding to the geostress state and the parameter of the surrounding rocks. Taking the parameters in the model test into the formula, it obtained that n =1.1. It matches well with the shape character of the fractured zones in the disassembled model after test.