深部多场耦合作用的非线性地应力构建方法

Method of nonlinear in-situ stress construction with deep multi-field coupling

  • 摘要: 深部高能级、大体量的工程灾害频发,难以预测和有效控制,而地应力是采矿工程、岩土工程和石油开采工程优化设计与动力灾害防治的重要依据。在分析深部地应力场时,现场测量理论与方法的局限性、原位保真取芯技术的困难性、地质条件的复杂性等因素都增加了对工程区域地应力场的认知与解释难度,影响了地应力判断结果的准确性。鄂尔多斯上海庙矿区是我国最大的胶结软岩质深部开采煤矿之一,主采煤层埋深超过1 000 m,温度分布局部差异性明显。区域各岩层历经多次构造运动,其断层及褶皱分布较多,水文地质条件复杂,岩溶水及孔隙水量大。鉴于上述众多因素对地应力场的耦合作用复杂、机理不明,决定了掌握地应力场分布状态需从多角度多方面分析研究。为此,首先介绍了几组适应于深部地应力场分布规律的边界载荷形式,并提出了一种新的深部地应力场非线性优化的算法——多元渐进迭代寻优算法,该方法能够保证高精度、快速获得全局最优解,十分适用深部复杂地应力场的反演与重构。其次,采用理论分析、现场测量及室内试验等方法,系统分析了深部地温分布规律,推导出深部非连续构造邻域内的温度分布解析解,并获得了矿区的地温资料、岩体热力学参数、软化系数及测点应力数据等。最后,基于研究区域的地质条件,构建了深部三维地质模型,考虑深部多场耦合特征、非连续构造特征及复杂地层属性特征等,反演重构出该区域的地温场及地应力场分布状态,其计算结果与实测值及现场地质资料等数据相吻合。

     

    Abstract: Deep high-energy and large-scale engineering disasters occur frequently, which are difficult to predict and effectively control.In-situ stress is an important basis for the optimization design and dynamic disaster prevention of mining engineering, geotechnical engineering and oil mining engineering.In the analysis of deep in-situ stress field, the limitation of field measurement theory and method, the difficulty of in-situ coring technology and the complexity of geological conditions all increase the difficulty of cognition and interpretation of in-situ stress field in engineering area, and affect the accuracy of in-situ stress assessment results.Shanghai Miao mining area in Ordos is one of the largest deep mining coal mines with cemented soft rock in China.The main mining coal seam is more than 1 000 m deep, and the local difference of temperature distribution is obvious.The regional strata have undergone many times of structural movement, with many faults and folds, complex hydrogeological conditions, large karst water and pore water.In view of the complex coupling effect of the above-mentioned factors on the ground stress field, and unclear mechanism, so it is necessary to analyze and study the distribution of in-situ stress field from many aspects.For this reason, firstly, several kinds of boundary load forms are introduced, which are suitable for the distribution law of the deep ground stress field, and a new nonlinear optimization algorithm is put forward for the deep in-situ stress field multiple progressive iterative optimization.This method can ensure high accuracy and fast global optimum solution, and is suitable for the inversion and reconstruction of deep complex in-stress field.Secondly, using the methods of theoretical analysis, field measurement and laboratory test, the distribution law of deep geothermal field is systematically analyzed, the analytical solution of temperature distribution in the neighborhood of deep discontinuous structure is derived.The geothermal data, thermodynamic parameters of rock mass, softening coefficient and stress data of measuring points are obtained.Finally, based on the geological conditions of the study area, a three-dimensional deep geological model is constructed.Considering the coupling characteristics of deep multiple fields, discontinuous structure and the complex stratum attributes, the distribution law of the geothermal field and the distribution state of the ground stress field in the area are reconstructed by inversion.The calculated results are consistent with the measured values and field geological data.

     

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