考虑应力分区的超长深埋隧洞地应力场精细反演方法研究

Accurate identification of distribution characteristics of geostress is an essential prerequisite for line project optimization design, effective disaster prevention and control of surrounding rock mass in deep-buried tunnel. As the conventional back analysis methods lack accuracy in initial geostress analysis of super-long and deep-buried tunnels, and cannot take into account the stress zoning effect, the project takes long distance and deep buried water conveyance tunnel as research background, and the comprehensive research approaches including regional geological background analysis, geostress measurement results interpretation, and focal mechanism solution analysis are conducted. Then, the controlling factors, the principal and implementation plan for the stress field zoning of super-long and deep-buried tunnel are proposed. Combining theoretical analysis with numerical simulation, the variation characteristics of the stress state of surrounding rock mass under different combination weight of normal stress and shear stress can be obtained by back analysis method. Then, the back analysis objective function which reflects the influence of normal stress and shear stress is set up. After that, the equilibrium condition of numerical software algorithms in elastoplastic state is studied so as to gain the accurate loading method of geostress field considering the effect of stress field zone. On the basis, combing the two-stage back analysis method, a new refined back analysis method for geostress field of super-long and deep-buried tunnel is proposed, which can be applied and verified in the studied project. The results above have important engineering application value for rational axis layout, surrounding rock mass stability, failure mode identification and prediction of surrounding rock mass in high in-situ stress zone of super-long and deep-buried tunnel. Meanwhile, the results are also of great significance to develop inversion theory of geostress field under complex conditions.

准确识别初始地应力分布特征，是实现线路工程优化设计、深埋隧洞围岩灾变有效防治的重要前提。针对现有反演方法应用于超长深埋隧洞时反演精度低，且未合理反映应力分区现象等问题，本项目以长距离深埋输水隧洞为背景，采用区域构造地质分析、地应力测试成果解析、震源机制解成果分析等手段，提出超长深埋隧洞应力分区的主控指标及分区方法。将理论分析与数值模拟相结合，揭示正应力与剪应力不同权重组合下反演获得的围岩应力状态变化规律，建立合理反映正应力与剪应力影响的反演目标函数，阐明弹塑性条件下数值软件在平衡时满足的算法条件，构建反映应力分区特征的地应力场精确加载方案，继而融合二次反演思想，提出适合超长深埋隧洞地应力场精细反演新方法，并利用依托工程进行验证。研究成果对超长深埋隧洞轴线的合理布置、围岩稳定性评价、高地应力区围岩破坏模式识别及预测具有重要的工程应用价值，同时对发展复杂条件下地应力场反演理论也具有显著意义。

本报告为国家自然科学基金青年项目“考虑应力分区的超长深埋隧洞地应力场精细反演方法研究（编号：51609018）”的结题/成果报告。.本项目通过对超长深埋隧洞地应力特征进行研究，建立了应力分区主控指标及方法，优化了地应力场反演目标函数，实现了弹塑性条件下地应力场平衡时满足的算法条件及加载方案，形成了一套适用于超长深埋隧洞地应力场精细反演方法。主要成果如下：.（1）发展了一种适用于超长深埋隧洞的应力分区方法。该方法以主应力方向、应力量值及测压系数、应力场类型、断层力学性质、震源机制解及断层滑动反演成果等为主控指标，以同一分区下各主控指标整体一致性较好为原则，实现了对复杂条件下跨越多个地质构造单元下的应力场应力分区的准确划分。.（2）构建了正应力与剪应力不等权重下的应力场反演目标函数。理论推导了不等权重下的应力场反演目标函数，同时结合数值模拟手段，构建了自重应力场和构造应力场下围岩的典型破坏特征及相应的目标应力场，通过对不同权重组合下的目标应力场进行反演分析，获得了正应力与剪应力权重对围岩应力状态的影响规律。.（3）实现了弹塑性条件下反映应力分区特征的地应力场加载方案。该方法基于较常用的摩尔-库伦本构模型，实现了不满足强度条件的单元应力修正方法，并利用FISH语言及MATLAB环境下的C语言程序，建立了反映应力分区特征的地应力场加载方案并实现单元应力与节点平衡的方法。.（4）提出了一种考虑应力分区特征的超长线路工程地应力场精细反演方法。该方法兼顾了大范围地形地貌、地质构造及非均匀性岩层等大尺度因素，以及小规模构造及局部开挖等小尺度因素影响，反演获得的应力场准确性更高，为复杂条件下超长线路工程岩体地应力场反演分析提供了一种新的实现途径。