锚杆支护条件下应变型岩爆过程研究

发布时间：2018-12-09 10:01

【摘要】：岩爆是处于高地应力状态下的岩体,在某种因素的作用下突然释放弹性应变能的动力现象,频繁发生于地下工程施工过程中,不仅威胁人员、机械安全,还制约经济发展和社会建设,已成为深部地下工程中最突出的地质灾害之一。目前,普遍采用锚杆支护的形式来防治岩爆,但从工程现场防治效果来看并不理想,许多已采用锚杆支护系统支护的隧洞仍发生了强烈的岩爆。因此,亟需开展相应的研究去揭示锚杆支护条件下应变型岩爆的发生过程与机理。本文分别从物理岩爆试验和数值模拟试验两个角度来揭示锚杆支护条件下应变型岩爆的过程。前者利用新型刚性真三轴岩爆试验机,以白色花岗岩岩样为试验对象,通过改变岩样上锚杆的数量与位置进行室内物理岩爆试验,再现了岩体在高地应力水平下采取锚杆支护时所发生的岩爆,并借助高速摄像系统、数字影像运动分析软件等试验设备,多维度记录岩爆弹射破坏全过程。后者利用UDEC二维离散元软件,模拟锚杆支护条件下花岗岩试样的岩爆过程,并以锦屏二级水电站施工过程中遭遇的一次岩爆实例为背景,模拟了不同密度的锚杆支护条件下隧洞的岩爆过程。研究结果表明:1、锚杆支护条件下的岩爆过程在宏观上与无支护条件下相似,包括颗粒弹射、劈裂成板、剪切成块、板折弹射四个阶段,但在细观上有所不同,表现为岩爆破坏始于锚杆与锚杆之间的区域,出现颗粒弹射现象,其中微裂纹向岩体深部发展并逐渐贯穿,引起块体弹射,从而打破了锚杆支护系统的整体性,造成岩体松动,锚杆法向应力急剧下降,锚杆加固作用减弱,锚固区域岩体最终也发生破坏。2、锚杆支护条件下锚杆与锚杆之间的岩体成为岩爆始发的薄弱地带,且岩爆一旦发生,危害相较无锚条件更严重,而锚杆并未充分发挥作用。3、在高地应力水平下,一味加密锚杆不能杜绝岩爆发生,但不同密度锚杆支护条件下的岩爆特征不一:在高密度锚杆支护条件下,由于薄弱地带不明显,岩爆造成围岩与锚杆联合体整体性破坏;在低密度锚杆支护下,由于薄弱地带的存在,岩爆破坏始于锚杆与锚杆之间的岩体并引起该区域岩体发生弹射,且岩爆破坏范围随锚杆密度增大而减小。
[Abstract]:Rock burst is a dynamic phenomenon of releasing elastic strain energy under the action of some factors, which occurs frequently in the construction process of underground engineering. It not only threatens the safety of personnel, but also the safety of machinery. It also restricts economic development and social construction, and has become one of the most prominent geological disasters in deep underground engineering. At present, bolt support is widely used to prevent rockburst, but the effect of prevention and control is not ideal. Many tunnels which have been supported by bolting system still have strong rockburst. Therefore, it is urgent to carry out relevant research to reveal the occurrence process and mechanism of strain type rockburst under bolt support. In this paper, the process of strain type rockburst under bolt support is revealed from physical rock burst test and numerical simulation test. The former uses a new rigid true triaxial rockburst tester and takes the white granite sample as the test object. The indoor physical rockburst test is carried out by changing the number and position of the anchor rod on the rock sample. The rock burst occurred when the rock mass is supported by bolt under high ground stress level is reproduced. With the help of high speed camera system, digital image motion analysis software and other test equipment, the whole process of rock burst ejection damage is recorded in multiple dimensions. In the latter case, the rock burst process of granite specimen under bolt support is simulated by using UDEC two-dimensional discrete element software, and the background is a case of rock burst encountered in the construction process of Jinping II Hydropower Station. The rock burst process of tunnel under different density of bolt support is simulated. The results show that: 1, the rock burst process under bolting condition is similar to that under the condition of no support, including four stages: pellet ejection, split plate forming, shearing block, plate folding ejection, but different in meso. The failure of rock burst begins in the area between anchor rod and anchor rod, and the phenomenon of particle ejection occurs, in which the micro-crack develops into the deep rock mass and gradually runs through, which causes block ejection, thus breaking the integrity of the bolt support system and resulting in rock mass loosening. The normal stress of the bolt decreases sharply, the reinforcement of the bolt weakens, and the rock mass in the anchoring area is destroyed. 2. The rock mass between the anchor rod and the anchor rod becomes the weak zone of the rock burst under the condition of anchor support, and once the rock burst occurs, The damage is more serious than the condition without anchor, but the anchor does not play a full role. 3. Under the high ground stress level, the rock burst can not be stopped by infilling the anchor. However, the characteristics of rock burst under different density bolt support conditions are different: under the condition of high density bolt support, the rock burst results in the failure of rock mass and bolt association because the weak zone is not obvious; Under the low density bolt support, the rock burst failure begins with the rock mass between the anchor rod and causes the ejection of the rock mass in this area because of the existence of the weak zone, and the range of the rock burst failure decreases with the increase of the bolt density.
【学位授予单位】：广西大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TV554

【相似文献】