跨活动断裂隧洞工程赋存区域地应力场分布特征研究

Study of distribution characteristics of in-situ stress field in occurrence area of crossing active fault tunnel engineering

初始地应力的方向、量值和分布形式是影响岩石地下工程围岩应力、变形和破坏模式的重要因素,在工程区域难以开展大量实测工作,且实测结果具有相当的离散性,引入数值分析方法和数学理论对地应力场综合分析是有效的解决手段之一。结合滇中引水香炉山隧洞穿越龙蟠-乔后断裂段(楚波–白汉场断裂南段)工程,针对实测结果中方向结果离散性较大的问题,基于中国现代构造地应力场特征,对丽江地区复合断裂对区域地应力场影响的理论分析与数值模拟,获取了地应力场方向的定性认识。基于钻孔测试成果,通过基于多元线性回归的三维地应力场反演获取了地应力场方向与量值的定量认识。获得的初步结果表明,龙蟠–乔后断裂F10运动形式以正断错动为主;左旋走滑为辅的滑动,受其影响隧洞工程在穿越F10断裂部位的主应力发生偏转,偏转后最大主应力方向近似平行或小夹角相交于F10断裂走向;反演获得的香炉山隧洞趋近F10-1、F10-2段最大主应力量值范围为13~19 MPa,中间主应力为11~16 MPa,最小主应力为9~13 MPa,应力量值较高,并呈现δ_H>δ_z>δ_h(H、h分别为最大、最小水平主应力)的特征;F10断裂F10-1、F10-2主断带成为地应力场的控制性边界,其间应力量值明显小于上下两盘岩体,F10-1、F10-2主断带间岩体最大主应力量值范围在9~10 MPa,最小主应力量值范围在7~10 MPa,地应力最大主应力方向与隧洞纵轴线以约60°夹角相交,相交角度较大,对隧洞稳定性影响较大。

The direction, magnitude and distribution of in-situ stress are important factors affecting the deformation and failure modes of underground engineering. It is difficult to carry out a lot of measuring test work in the engineering area; the measured results may be of great discreteness. Therefore, it is one of the effective methods to introduce the numerical analysis method and mathematical theory to analyze the in-situ stress field synthetically. This paper is based on the Xianlushan water dispersion tunnel that planned to across the active Longpan-Qiaohou fault, and aims to solve the problem of large discreteness of directional results in measured results. Qualitative understanding of the direction of in-situ stress field is firstly obtained by theoretical analysis and numerical simulation with the existing understanding of the tectonic stress field in China. Based on the test results, the quantitative understanding of the direction and magnitude of the in-situ stress field is obtained by the inversion of the three-dimensional in-situ stress field based on the multiple linear regression. The preliminary results obtained demonstrate that the movement form of Longpan-Qiaohou fault(F10) is mainly consists of normal sliding in conjunction with minor strike sliding. With its influence, the direction of the maximum principal in-situ stress is approximately parallel or small angle intersecting with the trend of F10. The regressed maximum principal in-situ stress for the rock mass near the tunnel will be 13-19 MPa; and the corresponding intermediate principal stress will be 11-16 MPa; and 9-13 MPa for the minimum principal stress. The stress level is relatively high, and presents a trend that H? >z? >h?(H? and h? are the maximum and minimum horizontal principal stresses respectively). F10-1 and F10-2 become the control boundary of the in-situ field, and the stress level between the F10-1 and F10-2 is obviously smaller than the upper and lower rock mass, i.e. 9-10 MPa for the maximum principal in-situ stress, and 7-10 MPa for the minimum principal stress. The maximum principal stress direction of in-situ stress intersects with the longitudinal axis of tunnel with an angle of about 60 degrees, which has a negative impact on the stability of the tunnel.