大岗山深埋硬岩公路隧道岩爆预测

Rockburst Prediction of Dagangshan Deep Buried Hard Rock Highway Tunnel

位于川西和青藏高原接触带的长大深埋硬岩公路隧道建设面临极大的岩爆危害,对其岩爆倾向性的准确预测是解决这一瓶颈问题的关键手段。以泸石高速大岗山隧道为工程背景,基于地勘中地形地貌、地质构造、岩石力学参数和地应力实测数据资料,采用数值模拟和数理统计相结合的方法,反演分析隧址区全线初始地应力场,系统分析了大岗山隧道各断面开挖洞周围岩二次应力,基于应力判据法对其岩爆发生情况进行了综合预测。结果表明:隧道全线地应力场分布规律以竖向应力为主,竖向应力量值最大达33.25 MPa,且局部地应力复杂,水平构造作用明显,以NWW-SEE向挤压作用为主,具备发生岩爆条件;隧道埋深大于408 m时有中等、强烈岩爆活动,中等岩爆段长度占隧道全长的13.8%,强烈岩爆段长度占隧道全长的39.7%,且埋深大于450 m时岩爆在边墙部位发生;岩爆发生受地形地貌、地质构造影响显著,由于地应力在软弱岩体中得到释放,断裂带、辉绿岩脉内部无岩爆活动,而断裂带和沟谷地形会使其附近完整花岗岩段内出现地应力集中现象,从而加剧其岩爆烈度。

The construction of long and deep buried hard rock highway tunnels,which are located in the contact area of western Sichuan and Qinghai-Tibet Plateau,is facing great rockburst hazards.Accurate prediction of rockburst tendency is a key means to solve this bottleneck problem.The Dagangshan Tunnel of Lushi Expressway was used as the engineering background.The topography,geological structure,rock mechanics parameters and in-situ stress measurements from the geological survey reports were used,and the initial in-situ stress field of the whole line in the tunnel site area was inversely analyzed by combining numerical simulation and mathematical statistics.The secondary stress in the surrounding rock of each excavation cross-section of the Dagangshan Tunnel was systematically analyzed,and the rockburst occurrence was comprehensively predicted based on stress criteria.The results show that the distribution law of the in-situ stress field in the whole tunnel is dominated by vertical stress,the maximum vertical stress is 33.25 MPa.The local in-situ stress is complex,and the horizontal tectonic action is obvious,which is mainly NWW-SEE extrusion,the tunnel has the condition of a rockburst.When the buried depth of the tunnel is greater than 408 m,there are moderate and strong rockburst activities.The length of the moderate rockburst sections accounts for 13.8%of the total length of the tunnel,and the length of the strong rockburst sections accounts for 39.7%of the total length of the tunnel.When the buried depth is greater than 450 m,the rockburst occurs on the sidewall.The occurrence of rockburst is significantly affected by topography and geological structure.Due to the release of in-situ stress in the weak rock,there is no rockburst activity in the fault zone and diabase dikes,while the fault zone and gully terrain will cause in-situ stress concentration in nearby complete granite sections,thus aggravating its rockburst intensity.