川藏铁路长大深埋隧道地应力场反演分析

Inverse Analysis on In-situ Stress Field of Super-long and Deep Buried Tunnel in Chuan-Zang Railway

西南地区山高谷深,地质条件复杂,隧道工程建设过程中面临着巨大地质灾害风险。桑珠岭隧道作为川藏铁路林芝段的主要控制性工程之一,面临着超长、超埋深诱发高地应力风险,本文通过综合分析隧道区域构造环境与现场实测数据,利用Surfer、ANSYS等软件构建隧址区三维数值模型,采用应力试算法确定模型加载的边界条件,进一步使用基于有限差分法的FLAC3D模拟计算,获得桑珠岭隧址区范围的初始地应力场。对比分析可见地应力在方向与量值上基本吻合,且与区域构造定性分析结论基本一致。隧道轴线方向地应力场总体表现为:最大水平主应力(SH)>垂直主应力(Sv)>最小水平主应力(Sh),最大主应力方向N30°W^N45°E。基于强度理论分析,隧道深埋段地应力较大,岩爆发生可能性较高。建议施工期间,应加强超前地质预报与监测,确保施工安全。

Southwest China has high mountains and deep valleys,particularly the complex geological condition causing great risk pressure from geohazards during tunnel engineering construction. Sangzhuling tunnel,selected as a case study on the inversion of in-situ stress is one control project in La-lin section of Chuan-Zang railway. Based on the geotectonic background analysis and field measurement,Surfer and ANSYS soft wares have been used to build the3 D numerical model. The boundary condition determined by geostress trial algorithm,then in-situ stress calculated by FLAC3 D. The inversion results are similar to the field measurement,including the value and the direction of stress.The conclusions are also agree to the geotectonic background analysis. The geostress features along the tunnel axis are: maximum horizontal principal stress(SH)> vertical principal stress(Sv)> minimum horizontal principal stress(Sh),and direction of maximum principal stress N30° W ~ N45° E. According to strength theory,high geostress is common in deep buried section,so that there is a high possibility of rock burst. Therefore,more attention must be paid to mitigating geohazards during construction by geological forecast and measurement.