深部硬岩剪切边界下应力诱发片帮的机制研究

Mechanism of stress-induced spalling of deep hard rocks under shear boundary condition

深部工程开挖现场发现硬岩的剪切破坏过程对地下工程稳定性具有重要影响。深埋硬岩隧洞边墙处片帮或板裂主要为压致拉裂的结果,可通过室内单轴压缩试验来模拟;而拱肩和底角处的片帮或板裂多数是在剪切边界下形成的,需通过室内完整硬岩直剪试验来再现。针对不同类型硬岩压致拉裂型片帮,已进行了相当深入的研究,但对完整硬岩剪切边界下应力诱发型片帮的直接研究还存在着不足。为了深入研究深埋硬岩隧洞片帮或板裂的形成机制,采用FLAC;软件模拟隧洞不同位置处围岩受开挖扰动的应力调整过程,根据中国锦屏地下实验室二期工程区域的片帮统计结果,将深埋硬岩隧洞片帮划分为压致拉裂型和剪切边界应力诱发型两类,提出剪切边界应力诱发型片帮形成过程的概念模型;利用完整大理岩设计了不同正应力下压剪破裂到剪切滑移的连续性直剪试验,试样典型片帮破坏结果验证了概念模型的合理性。

It is found that the shear behavior of hard rock is important for the stability of deep rock engineering.In a deeply-buried hard rock tunnel,the splitting of rock results in the spalling or slabbing in the side wall,which can be evaluated by the uniaxial compression test.However,the spalling or slabbing in the arch shoulder and foot is the result of rock failure under shear boundary condition,which should be estimated by the direct shear test.Although a lot of research work on the spalling or slabbing caused by rock splitting have been conducted,there are few direct shear tests on intact rocks to study the shear stress-induced spalling or slabbing.In order to better understand the mechanism of spalling or slabbing,this paper divides the spalling into two forms:splitting failure and shear stress-induced failure under shear boundary,and establishes the conceptual model of two types of spalling based on the statistical results of spalling at Chinese Jinping underground laboratory and numerical results of the deviatoric stress distribution of laboratory section using the FLAC;.A series of direct shear tests of intact marbles,which can achieve the shear failure and shear slip continuously,is conducted to verify the proposed conceptual model of spalling or slabbing.