深部圆形隧洞板裂屈曲岩爆的模拟试验研究

Experimental modelling on rockburst in deep hard rock circular tunnels

为了深入认识深部圆形隧洞中板裂屈曲岩爆的发生机制,采用大尺寸真三轴岩石试验系统对含预制孔洞红砂岩立方体(100 mm×100 mm×100 mm)试样进行模拟试验研究。首先根据地应力随深度分布规律,在水平向垂直隧洞轴向方向设定最小主应力,竖直向垂直隧洞轴向方向设定最大主应力,在3个方向分别加载到初始应力状态。然后保持另外2个方向应力不变,在竖直向垂直隧洞轴向方向进行加载直至隧洞洞壁围岩发生破坏,并且在保证试样整体不发生破坏条件下,逐级加载至洞壁发生岩爆。利用安装的微型摄像机对试验过程中洞壁围岩破坏全过程进行实时监测和记录,结合三维加载和洞壁受力情况,再现了深埋硬岩圆形隧洞板裂屈曲岩爆全过程。研究结果表明:岩爆过程可划分为平静期、细颗粒弹射和剥落期、板裂屈曲破坏和强烈破坏四个时期。岩爆可滞后应力发生,具有时间效应,并且受加载率影响明显。岩爆破坏深度达到更高静应力水平下的稳定状态,形成的V–型槽具有应力不敏感期;通过合理优化隧洞断面几何参数,可发挥结构强度尺寸效应,对岩爆发生起一定抑制作用。

In order to understand the mechanism of slab buckling rockburst in deep tunnels in hard-rock,a large scale true-triaxial rock test system was used in the modelling experiments on the red sandstone samples（100 mm× 100 mm×100 mm） with a prefabricated hole. The minimum principal stress was set in the horizontal direction perpendicular to the axial direction of the tunnel,the maximum principal stress was set in the vertical direction perpendicular to the axial direction of the tunnel and the initial stress state was achieved in three directions. The loading in the vertical direction perpendicular to the axial direction of the tunnel was increased until the tunnel wall began to damage, while the initial stresses in the other two directions were maintained the same. The stepwise loading was executed until the rockburst occurred while the specimen as a whole was not completely damaged. The whole process of rockburst occurred in tunnel wall during the test was monitored and recorded in real time with a miniature camera installed. The entire process of slab buckling rockburst of the deep hard rock tunnel is thus reproduced. The results show that the slab buckling rockburst can be divided into four periods,i.e.,the quiet period,the fine particle ejection and peeling period,the slab buckling damage and the strong damage. The slab buckling rockburst may occur lagging behind the stress,has a time effect,and is obviously affected by the loading rate. The failure depth of slab buckling rockburst reaches the stable state of higher static stress level. The formation of the V-shaped notch has a stress insensitive period. The optimization of geometric parameters of the tunnel cross-section plays a role in the size effect of the structural strength,which has a certain inhibitory effect on the slab buckling rockburst.