基于原生裂隙重张试验确定围岩块体边界法向应力分布规律研究

Study of distribution rule of wall rock block boundaries normal stress based on reopening test of preexisting fractures

由于地下工程处于一定水平的地应力环境中,块体边界法向应力概化的正确与否直接关系到块体的稳定性分析结果,现通过实测途径确定块体边界法向应力的研究还较少。基于大型地下厂房块体稳定性分析,通过在块体范围及邻区不同方向布置多个钻孔,首次将原生裂隙重张试验引入到块体边界法向应力的测定,对开挖后与块体主要边界产状相近的所有原生裂隙的法向应力进行了测试,成功取得了块体边界上的法向应力状态及其空间变化规律。研究结果表明:洞室开挖完成后,块体边界应力分布不均匀,但具一定规律,垂直向表现为从浅部到深部结构面的法向应力依次增大,在水平向上,随与洞室开挖面距离的增大而增大;结构面的法向应力实测值稍小于基于围岩应力的估算值,但总体一致。该成果可为确定围岩块体的边界力学状态和应力模型简化提供参考和依据。

As a result of underground engineering in a certain level of in-situ stress condition of surrounding rock, the stress environment is different from the surface slope. It directly relates to the block stability analysis results which the block boundary normal stress quantification is correct or not. Study of block boundaries normal stress by field measurement is not common. Based on stability analysis of a large underground powerhouse block, several different direct boreholes are placed in the block and adjacent areas;the method of preexisting fractures reopening tests is used to determinate block boundary normal stress firstly;and the normal stress state and rules of spatial change of preexisting fractures that occurrence similar to block boundary are successfully acquired. Research results show that, after the completion of excavation, distribution of block boundary stress is not uniform, but with a certain rule;the normal stress of structural surface increases from shallow to deep in the vertical direction, and increases with the excavation surface distance increasing in the horizontal direction. The measurement data of normal stress are less than the calculated values based on the method of surrounding rock stress; but the overall consensus. The results provide references for determining block boundary condition and simplifying stress model.