深部三维圆形洞室岩爆过程的模拟试验

Experimental simulation on rockburst process of deep three-dimensional circular cavern

为了模拟深部圆形洞室三维受力情况下岩爆的发生过程,以具有极强岩爆倾向性的花岗岩作为试验材料,利用自行研制的TRW-3000岩石真三轴电液伺服诱变试验机,对含直径50 mm贯穿圆形孔洞的100 mm×100 mm×100 mm立方体花岗岩试样进行了三向不等压加载试验。试验首先模拟1 000 m深度的初始应力环境,以垂直于洞室轴向的水平方向作为最小主应力方向,通过增加竖直方向应力模拟应力调整过程诱发岩爆情况,并借助三维加载岩样内部结构破坏实时视频监控系统监控洞壁破坏情况。试验结果表明,岩爆过程可以划分为平静阶段、颗粒弹射阶段、岩片剥落和爆裂阶段,洞壁两侧中间部位应力集中系数最高,最先产生破坏,然后沿径向向深部发展,最终形成两个对称型的V型槽。圆形洞室洞壁两侧破坏的3个典型受力节点,符合深部工程中统计得到的无支护圆形巷道的远场应力状态与破坏模式之间的关系,达到了模拟的效果。利用现有的4种岩爆判据进行了分析,判别结果与试验过程中拍摄到的洞壁破坏情况基本一致。洞壁的破坏伴随着声发射计数增加和能量升高,岩爆越剧烈,声发射越活跃。

To simulate the rockburst process of deep circular cavern under three-dimensional （3D） stress conditions, the granite material with extremely strong rockburst tendency was used for testing. True-triaxial compression tests were conducted on the cubic granite sample （100 mm×100 mm×100 mm cube granite sample with a diameter of 50 mm through circular hole） by using a self-developed TRW-3000 true-triaxial rock electro-hydraulic servo mutation testing machine. In the experiment, an initial stress environment of 1 000 m depth was simulated. Then, the stress in the vertical direction was increased gradually, and the hole wall was monitored with a real-time micro-camera and acoustic emission （AE） device. The results show that failure process can be divided into four stages, i.e., calm stage, pellet ejection stage, rock exfoliation stage and rockburst stage. The middle parts of the circular hole have the highest stress concentration factor and the damage is initiated. Then cracks develop along the radial direction to the deep part of the tunnel, and ultimately form two symmetrical V-shaped notches. Three typical loading points reflecting the failure states of the hole wall are in line with the statistical relationship of the far field stress state and failure mode of deep circular roadway without support. Four kinds of rockburst criteria are also applied to analyse failure states of the hole wall under different loading conditions, and the results are consistent with the failure states recorded in the testing process. The failure of the wall is accompanied by an increase of AE count and AE energy. The more severe the rockburst is, the more active is the AE.