动力扰动下深部开挖洞室围岩分层断裂破坏机制模型试验研究

Model test study of mechanism of layered fracture within surrounding rock of tunnels in deep stratum tunnelling under dynamic disturbance

为研究动、静组合加载下深部巷道围岩分区破裂化的机制,在Instron电液伺服材料试验机上对用石膏制作的深部洞室模型进行了动、静组合加载试验。为进一步分析动、静组合加载下深部巷道围岩分层断裂化的力学本质,将动、静组合加载下深部巷道围岩近似视为若干个二维动、静组合加载试样的组合体,并用红砂岩试样进行了二维动、静组合加载试验。试验结果表明,巷道轴向应力为最大主应力且大于一定值时,围岩会发生分层断裂现象;巷道轴向应力为最大主应力且与外部扰动应力叠加达到一定值时,围岩也会发生分层断裂现象;巷道直径越大,在相同的动、静组合加载条件下,更易发生分层断裂现象;相同直径的巷道,在不同的动、静组合加载作用下,巷道围岩分层断裂化程度不同,动、静组合应力叠加值越大,分层断裂化程度越严重;应力状态对试样裂纹扩展及分布方向起着主导作用,试样破裂面一般垂直于最小主应力方向(在最小主应力面内),与最大主应力方向一致;深部巷道围岩存在形成破裂圈的应力状态,这样的应力状态可诱发巷道围岩分区破裂现象的发生。

In order to investigate the mechanism on zonal disintegration within rockmass around deep tunnel under static-dynamic coupling loading,by using the Instron electro-hydraulic and servo-controlled material testing machine,the test of deep tunnel on plaster model subjected to static-dynamic coupling loading is carried out.In order to further analyze the mechanical nature of layered fracture of surrounding rock around deep tunnel under static-dynamic coupling loading,surrounding rock around deep tunnel is regarded approximately as a combination of samples subjected to biaxial static-dynamic coupling loading;and the biaxial test of red sandstone subjected to static-dynamic coupling loading is performed.Experiments indicate that layered fracture of surrounding rock around deep tunnel may occur when the axial stress of tunnel is the maximum principal stress and more than a certain value.Layered fracture of surrounding rock around deep tunnel may also occur when the axial stress of tunnel is the maximum principal stress and the superposition value of axial stress and external disturbance stress is more than a certain value.Larger tunnel diameter may make layered fracture of surrounding rock around deep tunnel occur more easily under the same static-dynamic coupling loading.The larger superposition value of axial stress and external disturbance stress may make more layered fracture of surrounding rock around deep tunnel occur under the same tunnel diameter.The failure mode of statically loaded sample under periodic dynamic load changes according to different static stress states;and fracture surface of sample is generally perpendicular to the minor principal stress direction（in plane of minor principal stress） and tends to agree with the maximum principal stress direction.There is the foregoing stress state in surrounding rock around deep tunnel triggering layered fracture,and then leading to zonal disintegration within rockmass around deep tunnel under static-dynamic coupling loading.