超深埋长隧道地应力场综合反分析方法与应用

Comprehensive Inversion Analysis Method and Application of Deep Buried Long Tunnel Geo-stress Field

在分析超深埋长隧道工程沿线地应力场时,大埋深、长洞线、复杂地质条件等因素增加了工程区地应力场的复杂性和认知难度,影响了地应力判断结果的准确性。锦屏山超深埋特长交通洞为中国埋深最大的交通隧道,最大埋深达到2 375 m、长度达到17.5 km,水压致裂法、应力解除法等常规的直接地应力测试方法仅适用于洞口等浅埋位置,难以直接测得深部的地应力数值,进而影响对整个区域地应力场的判断,客观信息的缺乏决定了要从其他多个角度去评估地应力场状态。首先借助峰值强度和残余强度应力包络线,揭示了隧道周边不同位置处围岩开挖响应所对应的应力状态,提出了超深埋长线形隧道工程地应力场分析工作流程。在锦屏山交通洞工程实践过程中,综合采用宏观地质判断、现场破坏现象分析、测试成果指示、应力集中区推断等方法,对地应力场分布特征进行了评估和解译。另外,由于岩组、褶皱、构造、地形等条件导致局部地应力异常,采用非连续数值分析方法分析了结构面、褶皱2种代表性因素对局部地应力场的影响。最后,基于上述研究成果,建立考虑了地形、褶皱和主要断层的整体高精度三维模型,利用褶皱构造和断裂构造在现今构造挤压作用下的响应方式揭示了沿线地应力存在的分区现象,为超深埋长线形隧道工程的地应力场判断提供了更加准确便利的方法。

When analysis on the geo-stress field of deep buried long tunnel, many factors such as large buried depth, long tunnel line and complex geological conditions increase the complexity of the geo-stress field and cognitive difficulty, and affect the accuracy of the results. Jinping mountain ultra-deep buried and ultra-long traffic tunnel is the largest deep buried traffic tunnel in our country, and the maximum depth is 2 375 m and the length reaches 17.5 km. The conventional direct in-situ stress test methods such as Hydraulic fracturing method, stress relief method applies, only can be applied to shallow buried deep, and is difficult to directly measure the geo-stress values. The judgment of the whole regional stress field will be affected. Because of the lack of objective information, the state of stress field must be evaluated from other multiple angle. Firstly, by using the peak strength and residual strength stress envelope, the stress state corresponding to the excavation response of surrounding rock in different locations around the tunnel is revealed. The process of analyzing the stress field of deep buried and long line tunnel is proposed. In the construction process of Jinping traffic tunnel, the methods of macroscopic geological judgment, the failure phenomenon analysis, test results indicate, high stress concentration area estimation were combined to evaluate and interpret the stress field distribution characteristics. In addition, because the petrofabric, fold, structure, terrain conditions lead to local ground stress anomaly, the discrete numerical analysis method was used to analyze the structural plane and fold factors impact on the local stress field. Finally, based on the above research results, the high-precision three-dimensional model was established, including the whole terrain, main fault and fold. The subdivision of the geo-stress along the line is revealed by the response of the fold structure and the fault structure under the current tectonic compression. It provides a more accurate and convenient method to judge the geo-stress field of the deep buried and long line tunnel engineering.