深部高应力圆形隧洞内部卸荷条件下岩爆模拟试验和强度弱化效应研究

Rockburst simulation tests and strength-weakening effect of circular tunnels under deep high stresses and internal unloading conditions

为了模拟深部高应力圆形隧洞在内部卸荷条件下洞壁发生岩爆的过程,以具有中等岩爆倾向性的红砂岩作为试验材料,利用TRW–3000岩石真三轴电液伺服诱变试验系统,对100 mm×100 mm×100 mm立方体红砂岩试样开展了先加载后钻孔卸荷条件下的岩爆模拟试验。试验模拟500 m深度的二维应力状态,首先对试样加载至设定的初始应力状态,然后利用自主研发的岩石钻孔卸荷试验装置进行岩石内部钻孔卸荷(孔洞直径为25mm),之后在竖直方向加载至洞壁发生破坏,达到模拟效果后主动卸载。试验过程中,利用微型摄像机监控并记录洞壁的整个破坏过程。为了对比卸荷作用的影响,对预先贯穿孔洞(孔洞直径为25mm)的同尺寸红砂岩试样开展了先开孔后加载条件下的岩爆模拟试验。试验结果表明,2种试验条件下均可实现岩爆过程的模拟,整个试验过程均可以划分为平静阶段、颗粒弹射阶段、岩片剥落阶段,最终在洞壁两侧形成V型槽。与先开孔后加载试验相比,先加载后开孔试验中洞壁的初始破坏应力较低,洞壁更容易发生破坏,并且洞壁发生岩爆破坏的严重程度较强,产生的岩片尺寸较大,洞壁剥落岩片的总质量较高,形成的V型槽深度较深,破坏范围较广。试验对比结果表明,高应力岩石内部卸荷会对围岩造成一定程度和范围的损伤,诱发围岩产生明显的强度弱化效应。

To simulate the rockburst process of deep high stress circular tunnel sidewalls under internal unloading conditions,100 mm×100 mm×100 mm cube specimens from red sandstone with moderate rock burst tendency were prepared,and rockburst simulation tests under the condition of loading first and then drilling unloading were conducted using TRW–3000 rock true triaxial electro-hydraulic servo mutagenesis test system to simulate the two-dimensional stress state of 500 m depth. Firstly,the specimens were loaded to the set initial stress state,and then a self-developed drilling unloading test device(25 mm hole diameter) was used for rock internal unloading.Subsequently,the loading was applied in the vertical direction until the failure of the hole wall,and the active unloading was applied after the simulation effect was achieved. The rockburst process of the hole sidewall was monitored and recorded using a micro-camera during the tests. In order to compare the effect of unloading,rockburst simulation test was carried out on the same size red sandstone specimens with a prefabricated hole(25 mm hole diameter). The test results show that the rockburst process can be reproduced under these two test conditions. The whole test process can be divided into calm,particle ejection and rock fragment exfoliation stages. Finally,V-shaped notches were found on both sidewalls. Compared with the first drilling and then loading test,the initial failure stress of the hole sidewall in the loading first and then holing test is lower and the hole sidewall is more likely to be damaged. The test results indicate that the internal unloading of high stress rock will cause damage to the surrounding rock in a certain extent and range,and induce obvious strength-weakening effect to the surrounding rock.