地质体具有非均匀、非连续、流固耦合等特性。渗流在地质体的失稳破坏中具有两重性，一方面流体可以弱化地质体中节理、断层等结构面从而加剧地质灾害的发生；另一方面，基于渗流的水力压裂技术成功应用于油气开采、防治冲击地压等领域从而提高工程效益。渗流是地质体变形破裂的主要因素，但是流体与地质体的相互作用研究尚有不足，因此建立渗流作用下地质体变形破裂的高精度计算方法是十分有必要的。
本文首先提出了一种任意单元刚体运动及弹性变形一体化计算方法，用于模拟地质体的连续变形阶段；其次，发展了一套岩体破裂的自适应计算方法，实现地质体内部裂缝扩展路径的精确模拟；然后建立了三维岩体流场-破裂耦合计算方法，刻画流体驱动下的岩体破裂过程；最后在实际工程中应用，分析水力压裂作用对煤层坚硬顶板垮落的影响。主要研究内容和结论如下：
（1） 从能量角度出发，选取刚体运动的平动位移、角位移，以及表征弹性变形的应变作为独立的广义变量，基于拉格朗日方程，提出任意单元刚体运动及弹性变形一体化计算方法。通过分解单元，将节点边界转化为广义变量的边界问题，完成了针对该方法的几何边界条件施加。在此基础上发展其高阶形式，实现地质体连续变形阶段应力场的精确模拟。单摆运动、重力场求解以及一维杆弹性波传播等数值算例验证该方法在计算转动问题、静态问题、动态问题方面的正确性和可靠性，最后通过悬臂梁案例验证该方法高阶形式在计算连续变形方面的精确性。
（2） 在上述计算方法的基础上，引入应变强度分布准则，选取破裂度作为裂缝起裂依据，依据最大拉应力-摩尔库仑复合强度准则判断裂缝扩展方向，从而建立岩体破裂的自适应计算方法，并且基于BP神经网络模型发展一种新的网格剖分算法，实现地质体内部裂缝扩展路径的精确、高效计算。通过三点弯曲梁、含孔洞四点弯曲梁和三轴压缩数值案例验证了该方法在拉伸以及剪切破坏形式下的裂缝扩展路径的准确性。
（3） 基于弹簧元模型，发展三维渗流弹簧元计算方法，在此基础上建立三维岩体流场-破裂耦合数值计算方法，解决流体驱动下岩体的破裂问题。该方法采用连续-非连续单元法计算岩体的变形和破裂，采用渗流弹簧元计算流体在裂隙通道中的流动以及流体在岩体内部的孔隙渗流。通过四个理论解和一个实验现象的对比分析，发现该方法可以精确捕捉裂隙通道和岩体内部的流体压力以及精准刻画流体作用下的岩体裂缝形态，最后一个圆盘水力压裂模拟说明该方法不仅可以描述裂缝面内和岩体基质中的流体压力分布，而且同时可以跟踪岩体内部裂缝的萌生、扩展以及贯通过程。
（4） 根据本文发展的计算方法，开展布尔台煤矿4-2煤层顶板水力压裂数值模拟。首先根据4-2煤层建立巴西圆盘试样，数值模拟了巴西圆盘劈裂过程，其裂缝扩展形态以及加载点力和位移关系均与实验解吻合良好；其次从流体压力、垮落步距和竖向应力三个方面数值分析了水力压裂技术对4-2煤层上方坚硬顶板的影响，说明水力压裂技术能够有效弱化顶板岩石强度、缩短垮落步距，达到坚硬煤层顶板下井下工作面的安全高效回采。

Geological bodies have the characteristics of non-uniformity, discontinuity, fluid-solid interaction and so on. Seepage has duality in the instability and destruction of geological bodies. On the one hand, the fluid can weaken the structural surfaces such as joints and faults in geological bodies to aggravate the occurrence of geological disasters. On the other hand, hydraulic fracturing technology based on seepage has been successfully applied to oil and gas exploitation, prevention and control of impact pressure and other fields to improve engineering efficiency. Seepage is the main factor of deformation and rupture of geological bodies, but the interaction mechanism between fluids and geological bodies is still insufficient, so it is necessary to establish a high-precision numerical method for deformation and rupture of geological bodies under seepage.
An integrated numerical method of rigid body motion and elastic deformation of arbitrary elements is proposed for simulating the continuous deformation stage of geological body. An adaptive numerical method for rock mass rupture is developed to achieve accurate simulation of the cracks propagation paths inside geological body. A novel three-dimensional rock mass seepage-rupture coupling numerical method is established to depict the rock mass rupture process driven by fluid. The influence of hydraulic fracturing on the collapse of the hard roof of the coal seam is analyzed in the past.
Firstly, from the perspective of energy, an integrated numerical method of rigid body motion and elastic deformation of arbitrary element is proposed based on the Lagrange equation. In this method, the translational displacement, angular displacement of rigid body motion and strain of elastic deformation are selected as independent generalized variables. Based on the generalized variational principle, the geometric boundary conditions are applied. And the higher-order form of this method is developed to achieve accurate simulation of the stress field in the continuous deformation stage of geological body. Numerical examples such as pendulum motion, gravity field solving, and one-dimensional rod elastic wave propagation verify the correctness and reliability of the method in calculating rotational problems, static problems, and dynamic problems, and finally verify the accuracy of the higher-order form of the method in calculating continuous deformation through the cantilever beam case.Secondly, an adaptive numerical method for rock mass rupture based the above method is established. In this method, the fracture degree of the strain strength distribution criterion is selected as the basis for crack opening, and the crack propagation direction is judged according to the maximum tensile stress and Mohr-Coulomb composite strength criterion. A new meshing algorithm is developed based on the Back-Propagation neural network model to achieve accurate and efficient calculation of crack paropagation path inside the geological body. The accuracy of the crack propagation path in the form of tensile and shear failure is verified by numerical examples of three-point bending beam, four-point curved beam with a hole and uniaxial compression.
Thirdly, based on the spring element model, the three-dimensional seepage-spring element method is developed, and on this basis, a three-dimensional seepage-rupture coupling numerical method is established to solve the rupture problem of rock mass under fluid driven. This method uses the integrated calculation method of rigid body motion and elastic deformation of any element to calculate the deformation and rupture of rock mass, and seepage-spring element method is used to calculate the flow of fluid in the fracture channel and the filtration loss effect of fluid inside the rock mass. Through the comparison and analysis with four analytical solutions and one experimental phenomenon, the fracture pattern is predicted accurately and the poroelastic stress is caputred as well. In addition, the result of a disc with one injection hole suggests that this model can not only depict the fluid pressure distribution in fractures and pores of rock matrix, but also trace the initiation, propagation and intersection of cracks driven by fluid.
Finally, according to the numerical methods developed in this paper, the numerical simulation of hydraulic fracturing of 4-2 coal seam roof in Bourtai Coal Mine is carried out. Firstly, the Brazilian disc specimen was established according to the 4-2 coal seam, and the Brazilian disc splitting process was simulated numerically, and the results showed that the crack expansion morphology and the relationship of loading point force and the displacement were all in good agreement with the experimental solution. Secondly, the influence of hydraulic fracturing technology on the hard roof above the 4-2 coal seam was analyzed from the three aspects of fluid pressure, collapse step distance and vertical stress. The results indicated that the hydraulic fracturing technology could effectively weaken the rock strength of the roof plate, shorten the caving step, and achieve safe and efficient recovery of underground working face under hard coal seam roof.