裂隙岩体裂隙网络渗流场—应力场耦合的刚体元分析

基于裂隙岩体初始裂隙网络渗流的离散数值模型，首次采用新的数值方法－－刚体元方法进行裂隙岩体裂隙网络渗流场－应力场耦合分析，既避免了经典渗流理论不考虑介质应力的不足，又克服了工程岩体稳定性分析中简单考虑水渗流作用的缺陷。     

饱和多孔岩体中温度场渗流场应力场耦合分析

利用混合物理论,推导出裂隙岩体等效连续介质温度场、渗流场和应力场三场耦合的全耦合数学模型及其控制方程.采用全耦合求解法给出了控制方程的有限元表达式,编制了相应的二维有限元程序.给出的应用算例计算结果较好地反映了渗流、应力及温度场耦合作用下位移、孔隙水压力、温度的变化规律,表明了该计算模型与所开发的数值计算程序是合理和实用的.     

节理裂隙岩体渗流与应力耦合分析

在总结已有的饱和非饱和渗流模型的基础上,把裂隙岩体看作是离散网络模型,分析研究了含节理裂隙岩体的非饱和渗流特性,建立了裂隙网络饱和非饱和渗流模型,并推导了控制方程.对节理裂隙岩体中外力对裂隙渗流的影响进行了分析研究,提出了渗流场-应力场耦合的分析模型,推导出三维应力与裂隙水压力共同作用下一组平行裂隙组的渗流应力耦合关系式.     

油藏热流固耦合渗流问题的有限元方法

提出了一种有效实用的求解油藏热流固耦合渗流问题的数值计算方法。该方法以有限元法为主，结合有限差分法，用有限元法求解耦合温度场方程和岩石耦合变形方程，用有限差分法求解流体耦合渗流方程，发挥有限元法网格技术和单元划分灵活的特点及处理复杂的油藏边界优势，兼顾了有限差分法在流场分析方面的成熟应用，使复杂的热流固耦合数学模型得以完整求解，取得了单向有限元法或有限差分法难以取得的效果，是一种新型的油藏数值模拟方法。     

隧道开挖过程中复杂裂隙围岩的固流耦合分析

隧道通过裂隙岩体的含水区段时,人为扰动了裂隙岩体、地下水等构成的复杂地质系统,是造成各种涌水、突水、突泥事故的重要原因。为了研究复杂地质条件下隧道开挖过程中岩体变形、流体运移相互作用过程,探讨其对隧道涌、突水的影响,在上述复杂过程进行理论分析的基础上,根据深埋隧道围岩裂隙发育规模与工程尺度的关系,建立可以同时考虑不同级别裂隙网络的复杂裂隙岩体水力学模型,采用有限元法对复杂裂隙岩体中开挖隧道的固流耦合过程进行了数值模拟,模拟结果体现了主干裂隙在渗流中的强导水作用和网络状裂隙的贮水功能与渗流滞后效应,开挖过程中复杂裂隙岩体渗流场与应力场的耦合作用显著的增加了隧道围岩屈服区。     

裂隙岩体初始裂隙网络渗流模型研究

运用离散数学的图理论进行裂隙岩体裂隙网络连通性研究，建立了裂隙岩体初始裂隙网络渗流的离散数值模型，这一模型从根本上突破了经典的均质渗流理论。     

二维裂隙岩体渗流数值模拟技术研究

如何准确地描述岩体裂隙水的流动状态是一个重要课题.与原位实验相比,利用数值模拟方法研究裂隙岩体渗流问题,具有高效、经济、可重复性强等特点.然而,较准确的岩体裂隙网格模拟和裂隙水流动模拟系统的设计与实现,是数值模拟方法研究的两个难点.非连续裂隙网络仿真主要采用Monte Carlo技术,结合裂隙统计学特征,进行随机模拟.先研究区域内随机生成符合地质统计学规律的裂隙网络,再对渗流有贡献的裂隙进行筛选并自动离散,最后利用水量均衡原理计算出各节点的水头.通过开发相应的程序包,提高岩体裂隙渗流计算的规模和准确性,为进一步研究水在岩石中的作用打下基础.     

水力耦合裂隙岩体变形破坏机制研究进展

为深入了解水力耦合作用下裂隙岩体变形破坏机制,正确评价岩体工程的安全性和稳定性,通过收集整理国内外文献,系统综述了水力耦合完整岩体和裂隙岩体变形破坏方面研究的进展与成果.简述了水力耦合下完整岩体和裂隙岩体的力学特性,侧重总结了水力耦合单一裂隙岩体渗流公式,包括流量与隙宽指数n之间关系、渗透（导水）系数与正应力之间关系以及渗透特性与剪应力之间关系的数学公式.重点分析了水力耦合裂隙岩体变形破坏机制的最新研究进展,介绍了声发射（AE）、超声波（UT）、偏光显微镜（PM）、扫描电子显微镜（SEM）以及计算机断层摄影（CT）等先进的辅助试验技术在变形破坏分析中的应用.归纳了数学耦合模型、数值分析方法的优缺点及适用条件.最后,指出了当前水力耦合裂隙岩体研究中存在的一些问题,提出了一些指导性意见,并从几方面展望了未来的发展趋势,即机理研究从宏细观转向微观、数值模拟从粗糙转向精细、工程应用从水力耦合转向多场耦合.     

节理裂隙岩体渗流与应力耦合分析

在总结已有的饱和非饱和渗流模型的基础上，把裂隙岩体看作是离散网络模型，分析研究了含节理裂隙岩体的非饱和渗流特性，建立了裂隙网络饱和非饱和渗流模型，并推导了控制方程．对节理裂隙岩体中外力对裂隙渗流的影响进行了分析研究，提出了渗流场—应力场耦合的分析模型，推导出三维应力与裂隙水压力共同作用下一组平行裂隙组的渗流应力耦合关系式。     

裂隙水渗流潜水面迭代方法的探讨

针对裂隙岩体的渗流问题，引入潜水面单元的概念，探讨了裂隙网络中潜水面的迭代方法，并据此方法分析了潜水面的裂隙水渗流问题，证明该方法是可靠的。     

Simulation of hydraulic fracture utilizing numerical manifold method

A 2nd order numerical manifold method(NMM) based method is developed to simulate the hydraulic fractures propagating process in rock or concrete. The proposed method uses a weak coupling technique to analyze the fluid phase and solid phase. To study the seepage behavior of the fluid phase, all the fractures in solid are identified by a block cutting algorithm and form a flow network. Then the hydraulic heads at crack ends are solved. To study the deformation and destruction of solid phase, the 2-order NMM and sub-region boundary element method are combined to solve the stress-strain field. Crack growth is controlled by the well-accepted criterion, including the tension criterion or Mohr-Coulomb criterion for the initialization of cracks and the maximum circumferential stress theory for crack propagation. Once the crack growth occurs, the seepage and deformation analysis will be resolved in the next simulation step. Such weak coupling analysis will continue until the structure becomes stable or is destructed. Five examples are used to verify the new method. The results demonstrate that the method can solve the SIFs at crack tip and fluid flow in crack network precisely, and the method is effective in simulating the hydraulic facture problem. Besides, the NMM shows great convenience and is of high accuracy in simulating the crack growth problem.     

Two-dimensional numerical manifold method with multilayer covers

In order to reach the best numerical properties with the numerical manifold method (NMM), uniform finite element meshes are always favorite while constructing mathematical covers, where all the elements are congruent. In the presence of steep gradients or strong singularities, in principle, the locally-defined special functions can be added into the NMM space by means of the partition of unity, but they are not available to those complex problems with heterogeneity or nonlinearity, necessitating local refinement on uniform meshes. This is believed to be one of the most important open issues in NMM. In this study multilayer covers are proposed to solve this issue. In addition to the first layer cover which is the global cover and covers the whole problem domain, the second and higher layer covers with smaller elements, called local covers, are used to cover those local regions with steep gradients or strong singularities. The global cover and the local covers have their own partition of unity, and they all participate in the approximation to the solution. Being advantageous over the existing procedures, the proposed approach is easy to deal with any arbitrary-layer hanging nodes with no need to construct super-elements with variable number of edge nodes or introduce the Lagrange multipliers to enforce the continuity between small and big elements. With no limitation to cover layers, meanwhile, the creation of an even error distribution over the whole problem domain is significantly facilitated. Some typical examples with steep gradients or strong singularities are analyzed to demonstrate the capacity of the proposed approach.     

An h-adaptive numerical manifold method for solid mechanics problems

The numerical manifold method(NMM) features its dual cover systems, namely the mathematical cover and physical cover,which provide a unified framework for mechanics problems involving continuum and discontinuum deformation. Uniform finite element meshes can be and are usually used to construct the mathematical cover. Though this strategy can handle different kinds of problems in a unified way, it is not economical for cases with steep deformation gradients or singularities. In this paper, using the recovery-based error estimator, an h-adaptive NMM on quadtree meshes is proposed to deal with such cases. The quadtree meshes serve as the mathematical meshes, on which the local refinement is carried out. When the quadtree meshes are refined,the corresponding mathematical cover, physical cover and manifold elements are updated accordingly. To handle the hanging nodes in the quadtree meshes, we resort to mean value coordinates. Comparing to the refinement based on manifold elements,the proposed strategy guarantees consistent structured meshes throughout the adaptive process, thus retaining the unique feature of original NMM. In contrast with polygonal finite element method, an advantage of the proposed method is that the meshes do not need to conform to the crack face and material boundary, which means the adaptive NMM is very suitable for problems with complex geometric boundary. Several representative mechanics problems, including crack problems, are analyzed to investigate the effectiveness of the proposed method. It is demonstrated that the proposed adaptive NMM has higher accuracy and better performance comparing to uniform refinement strategy.     

An <Emphasis Type="Italic">h</Emphasis>-adaptive numerical manifold method for solid mechanics problems

The numerical manifold method (NMM) features its dual cover systems, namely the mathematical cover and physical cover, which provide a unified framework for mechanics problems involving continuum and discontinuum deformation. Uniform finite element meshes can be and are usually used to construct the mathematical cover. Though this strategy can handle different kinds of problems in a unified way, it is not economical for cases with steep deformation gradients or singularities. In this paper, using the recovery-based error estimator, an h-adaptive NMM on quadtree meshes is proposed to deal with such cases. The quadtree meshes serve as the mathematical meshes, on which the local refinement is carried out. When the quadtree meshes are refined, the corresponding mathematical cover, physical cover and manifold elements are updated accordingly. To handle the hanging nodes in the quadtree meshes, we resort to mean value coordinates. Comparing to the refinement based on manifold elements, the proposed strategy guarantees consistent structured meshes throughout the adaptive process, thus retaining the unique feature of original NMM. In contrast with polygonal finite element method, an advantage of the proposed method is that the meshes do not need to conform to the crack face and material boundary, which means the adaptive NMM is very suitable for problems with complex geometric boundary. Several representative mechanics problems, including crack problems, are analyzed to investigate the effectiveness of the proposed method. It is demonstrated that the proposed adaptive NMM has higher accuracy and better performance comparing to uniform refinement strategy.     

MRT-LBM-based numerical simulation of seepage flow through fractal fracture networks

The study on seepage flow passing through single fractures is essential and critical for understanding of the law of seepage flow passing through fracture networks and the coupling mechanisms of seepage field and stress field in rock masses. By using the fractal interpolation to reconstruct a natural coarse fracture, as well as taking into account the microstructure of the fracture, the numerical simulation of seepage flow passing through the coarse fractures with two distinct vertical scaling factors is conducted based on the MRT-LBM model of the lattice Boltzmann method. Then, after obtaining the length of the preferential flow pathway, the permeability of the two kinds of fractures is estimated respectively. In view of difficulties in locating the preferential flow pathway of natural fracture networks, by numerical tests a transect permeability weighted algorithm for estimating the fracture network permeability is proposed. The algorithm is not specific to one or more particular preferential flow pathways, but considers the contribution of each section to hinder the fluid passing through the medium. In order to apply the new algorithm, by capturing the structure of fracture networks based on the image-processing technique, the numerical simulations of seepage flow passing through two groups of natural fracture networks is carried out, the permeability is forecasted and the partial flows are reproduced for both cases. It is found that the preferential flow pathway emerges at the beginning of evolution, then is strengthened subsequently, and finally reaches a steady status. Furthermore, by using the proposed method some details on local flow can be clearly observed such as backflows and vortices at local branches can exist simultaneously and so forth, suggesting the validness of the proposed method for multiscale simulations of seepage flow.     

岩体渗流的数学模型和数值分析方法

在分析岩体渗透特性及其影响因素的基础上，建立了岩体渗流的数学模型；研究了岩体渗流的有限单元法，提出了适于解决裂隙结构渗流的节理单元，推导了相应的计算公式并编制了相应的计算机程序。对模型应用中的若干问题进行了探讨。     

数值流形方法在八结点有限元网格上的实现

数值流形方法常基于有限元法三结点或四结点单元.在八结点单元构成的网格上构建流形覆盖和权函数,采用拉格朗日乘子法施加位移约束条件,推导了分析静态问题的计算列式.无需细致网格划分即可更精确地分析具有曲线边界的区域,计算结果的误差能量模较有限元法降低超过一个量级.还提出另一套简明有效的覆盖函数,能降低求解规模近1/3.利用算例分析了这种方法两套覆盖函数的收敛率.对解答有体积闭锁的问题均有很高精度.     

小湾拱坝坝基含排水孔岩体渗流与应力耦合分析

小湾坝基岩体裂隙发育,坝基结构复杂且水推力巨大,为提高小湾坝基安全稳定性,基于含排水孔裂隙岩体渗流与应力耦合的复合单元算法,对小湾拱坝坝基含主排水孔系统裂隙岩体进行了三维渗流与应力应变耦合分析.通过算例分析,可以看出复合单元模型针对细部构造模拟时前处理简便快捷,且可真实反映裂隙、排水孔等细部构造的渗透特性;同时也可看出,小湾拱坝坝基考虑渗流与应力耦合时,水头等势线向坝基底区域集中,渗透坡降增加,同时坝基底渗流速度增加,下游区域流速有所减小.