考虑层状构造特征影响的岩体地应力场精细反演分析研究

    Inverse analysis method for in-situ stress field of rock mass considering influences of characteristics of layered structure

    • 摘要: 层状岩体及其层间剪切破碎带对厂区局部地应力场的量值和方向具有十分复杂的影响,准确获取复杂地质条件下厂区初始地应力场条件是分析层状岩体地下洞室围岩稳定性的先决条件,故提出考虑层状岩体对局部地应力场影响的二次反演分析方法。首先,针对影响地应力场规律的复杂河谷演化过程、地形地貌和构造作用等因素,发展了基于地层剥蚀模拟的侧压力系数法进行一次反演计算,得到大模型初始地应力场。其次,针对层状各向异性构造岩体对局部应力场的影响,建立层状岩体二次反演模型,并从一次反演应力场中插值计算等效节点力荷载来模拟构造作用,提出了基于等效构造作用的层状岩体地应力场二次反演方法。结合一次和二次反演方法,形成了层状岩体三维初始地应力场优化反演分析方法。最后,将该反演分析方法运用于贵阳抽水蓄能水电站地下厂房中,二次反演结果表明:计算得到的地应力场结果能够满足实测点处点吻合和反映河谷演化和层状岩体影响的场吻合要求;工程区地应力场受层面的影响,在层间剪切带边缘局部应力量值稍有增加,软岩层内应力释放明显,且局部应力场方向受岩层产状变化而发生不同程度的偏转扰动;深入分析了层状岩体各向异性力学性质对局部地应力场量值、方向和扰动范围的影响规律。

       

      Abstract: The layered rock mass and its interlayer shearing fracture zone have complex influences on the magnitude and direction of local stress field in underground engineering areas. Obtaining the initial in-situ stress field under complex geological conditions is the prerequisite for analyzing the stability of surrounding rock of underground caverns in layered rock mass. Firstly, aiming at the influences of evolution process, topography and tectonic action of a complex valley, a lateral pressure coefficient method based on the stratum denudation simulation is proposed for the first-stage inversion and the initial ground stress field of big model is obtained. Secondly, based on the influences of layered rock mass on local stress field, a second-stage inverse model for layered rock mass is established. The equivalent tectonic loads are obtained by the stress field calculated by interpolation from the big model, and the second-stage inverse analysis method based on the equivalent tectonic loads is proposed. Combined with the first and the second inverse methods, the optimal inverse analysis method for the three-dimensional initial in-situ stress field of layered rock mass is formed. Finally, the in-situ stress field of underground cavern of Guiyang pumped storage hydroelectric plant is inverted on account of the measured in-situ stress data. The secondary inverse results indicate that the inverse values of the in-situ stress field can meet the requirements of point coincidence at the measuring points and field coincidence reflecting the evolution process of the valley and influences of the layered rock mass. The local stress field in underground engineering areas is significantly affected by the interlayer shearing fracture zone, which is mainly manifested in the following aspects: (1) The local stress value increases slightly near the interface and releases in the soft rock layer. (2) The direction of the local stress field deflects differently due to change of the occurrence of rock strata. Using the proposed method, the influences of anisotropic mechanical properties of layered rock mass on the magnitude, direction and disturbance range of local in-situ stress field are deeply analyzed.

       

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