深切河谷区地应力场的非线性系统分析方法

地应力测试结果的代表性受断层及岩组条件、测点空间位置和测试方法精度等因素的影响较大。以往地应力模拟分析在引入地应力实测信息时,往往给各测点赋予相同的权重,使得离散测点和代表性不足的测点离差平方和较大,从而影响模拟分析精度。提出了深切河谷应力场非线性系统分析方法,该方法首先根据测试方法、地形地貌的影响及断层的扰动,对测点赋予不同的权重值;然后结合加权最小二乘法建立计算模型边界条件和地应力之间的加权目标函数;最后结合正交设计和智能优化反演方法,对数值计算模型边界条件与地应力之间的非线性映射关系和进行优化求解。该方法用于乌东德水电站坝址区岩体应力场的研究结果表明:计算值和测试结果的复相关系数达到了0. 89,在河床底部100 m的范围内存在明显的应力集中,且河床浅部岩体最大水平主应力方位与河流走向基本垂直,随着埋深的增加该方位朝场区主压应力优势方位靠近;边坡浅层岩体最大水平主应力方向与河流在该段走向呈小角度相交,随着竖直埋深的增加,最大水平主应力方位逐渐向NE向过渡,与河床部位相同高程部位的最大水平主应力方位一致;而深部岩体接近场区主压应力优势方向。

Nonlinear systematic analysis of in-situ stress field for deep-incised valley

The representativeness of in-situ stress test results is affected by faults and petrofabric condition, the testing location and accuracy of testing methods. When the test information was introduced to analyze in-situ stress field in previous study, the same weight values were assigned to different measured results, resulting larger square sum of deviations of discrete measured points and poor representative measured points relative, so the accuracy of simulation analysis was affected. We proposed a nonlinear system analysis method of in-situ stress field for deep incised valley in this paper, which assigns different weight values to different measured points based on considering the measuring methods, affection of topography and faults' distribution. Then, the weighted objective function between in-situ stress and boundary conditions was constructed by weighted least square method. At last, orthogonal design and intelligent optimization inversion method were applied to solve the nonlinear mapping relationship between boundary conditions of numerical simulation model and in-situ stress. This method was used in the analysis of in-situ stress field of Wudongde Hydropower Plant. The results showed that the multiple correlation coefficient between calculated results and measured results reaches 0.89. In the range of 100m riverbed, the stress concentration is obvious. In the shallow rock mass under the riverbed, the orientation of maximum horizontal principal stress is nearly perpendicular to river direction, and with the increase of burial depth, it is close to the dominant direction of principal compressive stress in the deep-incised valley field area. In the shallow rock mass of slope, the direction of maximum horizontal principal stress intersects with river trend by a small-angle, and with the increase of burial depth, it transits to NE trending gradually, which is consistent with the direction of maximum horizontal principal stress in the riverbed of same elevation. In deep buried rock mass, the direction of maximum horizontal principal stress is near to the dominant direction of principal compressive stress in the valley area.