煤层水力压裂典型裂缝形态分析与基本尺寸确定

分析煤层气井水力压裂时裂缝的典型类型与形状，建立水平缝与垂直缝的判别方法，推导由水平缝向垂直缝转变的临界深度计算公式，描述几种常见裂缝的形状和相应的形成条件。从断裂力学基本原理出发，分别推导在一定注入泵量和注入时间下，３种二维模型裂缝几何尺寸的基本计算公式。为水力压裂开采煤层气提供重要理论依据。     

综合利用位场及其梯度的频率域曲化平方法

根据位场理论，本文导出了直接利用位场及其垂直梯度的曲化平迭代计算公式，给出了其正则化稳定算法，研究了迭代计算公式的收敛性问题，最后，利用该方法对理论模型数据和实际资料进行了处理，两者计算结果都证明了该方法的有效性。     

一种新的可靠度计算方法及其在工程中的应用

利用神经网络拟合极限状态方程、几何法计算结构可靠度,并推导了基于神经网络的几何法计算公式。最后比较了该法与其他可靠度计算方法的精度以及计算效率,并将该法应用于实际工程当中。     

边坡变形系统失稳控制因素研究

通过对顺层变形几何非线性和连续变形物理非线性边坡模型的讨论，建立了边坡为形系统失稳的条件，找出影响系统稳定性的控制变量，并就控制变量的因素进行探讨，提出了人为调整控制变量，来防止边坡系统失稳措施的设想。     

利用位场连续复小波变换识辨磁场源(下)

基于齐次位场源的位场柯西小波变换，等效于位场向上延拓和求导两种运算相结合原理，建立了不同的理论模型，并编写了所有程序，通过合成资料的大量计算，对所有结果进行了验证与讨论。利用小波变换系数模沿极值轴线的变化特征，可以同时反演位场源的几何形状、埋深、倾角。实用于重磁资料自动化处理与解释，为磁场反演提供了一条新的途径。     

顺直河流横向紊动扩散系数

利用垂直紊动扩散系数及水利几何形态关系,借助于抛物线型断面形态方程,提出了顺直河道中局部水深沿横断面的分布,在此基础上确定了横向紊动扩散系数的断面分布及其平均值表达式,阐明了无量纲横向紊流扩散系数间的关系,计算的断面平均横向紊动扩散系数与138组试验资料吻合良好。比较结果表明,建立的顺直河道横向紊流扩散系数计算公式能给出与实测值最接近的预测值。与现有的其它横向紊流扩散系数计算公式相比,其公式在理论上更加合理,机理上更加清楚,并且具有最小的预测误差。     

上软下硬岩质地层浅埋大跨隧道松动压力计算

针对现有方法在上软下硬岩质地层中浅埋大跨隧道松动压力计算方面存在的问题,通过离散元数值模拟和正交试验,分析了围岩的松动破坏机制、风化层厚度和岩体中节理分布状态对隧道松动区形状和范围的影响规律及敏感性。结果表明：影响松动区的主要因素依次为风化层厚度、隧道埋深、贯通倾斜节理的倾角和间距、风化层水平节理间距;松动区可分为拱形和塌穿形两种类型,其边界曲线分别可用抛物线和乘幂函数近似表示。针对塌穿形松动区,通过回归分析建立了地表松动宽度和拱顶松动土条水平长度的计算公式。按照应力传递原理,在松动区内以梯形微分岩土条为对象,通过分层积分,推导出可反映节理产状和风化层厚度影响的浅埋大跨隧道围岩松动压力计算公式。工程实例计算表明,与现有方法相比,所提方法计算的松动压力值最小。     

河流纵向分散系数研究

研究了天然河流纵向分散系数理论公式及其参数的确定问题.借助于抛物型断面型态方程确定了河道垂线水深沿河宽的分布及流速分布对断面平均流速的偏离u‘的横向分布,给出了横向混合系数计算方法.在此基础上通过对Fischer的三重积分的直接求解,建立了新的天然河流纵向分散系数计算公式.这一新建立的纵向分散系数计算公式与原有的有代表性的经验公式以及26条美国河流上实测的59组资料进行了比较,比较结果表明,本文建立的纵向分散系数计算公式能给出与实测纵向分散系数最接近的预测值.与现有的其它纵向分散系数计算公式相比,本文建立的天然河流纵向分散系数公式理论上更加合理,机理上更加清楚,并且具有最小的预测误差.     

城市管网数据模型与网络逻辑拓扑关系

城市市政网络系统是城市地理信息的重要组成部分, 基于ArcGIS地理信息系统平台, 运用Catalog, Geodatabase中间件技术, 构造十堰市燃气管网数据库, 将GIS外部的关系数据库管理系统(RGBMS) 与燃气管网调度管理系统(DMS) 有机地集成在基于GIS空间数据的可视化管理平台上, 实现了对管线几何关系数据、逻辑关系数据和实时动态监测数据的统一管理.通过管线要素类和要素集建立市政管网空间数据的几何拓扑关系, 通过Catalog和Geodatabase建立管网的逻辑拓扑规则和准确表征专业管道物理网络的各种连接关系及其流动系统的动力学关系, 在实时监控网络数据接口的支持下, 通过SKADA和RTU系统获取管道流体的物理特征实时数据, 为燃气调度和事故预警提供动态监测空间位置信息和管道维护检修的决策支持信息.系统集成基于C/S和B/S体系结构, 具有实际应用价值.      

藏北羌塘地区地层新资料

新的牙形石化石资料证实在羌塘北部地区有泥盆纪查桑组地层，它是该盆地保存的最古老海相沉积地层，羌塘地区中西部广大地区上侏罗统索瓦组顶部产有丰富的以Virgatosphinctes和Aulacosphinctes两属为主的菊石化石，可初步建立5个菊石组合，其中Berriasella和Blanfordiceras菊石的出现使最高海相层位上延至提塘阶顶部或贝利阿斯阶，而圆笠虫(Orbitolina)、似异卷虫（Heterohelix）出现可能反映有海相白垩纪地层的存在，在晚三叠世肖茶卡组中发现有Epigondolella牙形石动物群，这是我国晚三叠世最高位牙形石带又一产地，首次在双湖比隆组油页岩剖面顶部发现产Harploceras sp.菊石化石的层位，时代属早上托阿尔斯（Toarcian）。解决了这一特殊沉积地层单位长期争论的时代归属问题，并指出它与早侏罗世海侵高峰期全球缺氧事件有关。     

榆神矿区采煤失水危险性分区研究

以榆神矿区区域地质资料为依据,总结了该区煤层与含(隔)水层空间组合类型; 采用三维数值模拟方法,根据塑性条件、破坏准则及应力判别,模拟首采煤层与含(隔)水层空间组合类型下导水裂隙带高度; 通过对比钻孔探测法与数值模拟法,发现数值模拟法具有可行性; 利用模拟结果,绘制矿区导水裂隙带高度空间分布图,总结矿区导水裂隙带高度的整体分布规律; 对比导水裂隙带高度与其首采煤层上覆岩层厚度,总结矿区采煤失水危险性,并进行采煤失水危险性分区; 通过控制采煤失水危险区域的采厚可以达到“保水采煤”的效果。本研究对榆神矿区后期安全生产具有重要的理论意义与实际价值。     

Determination of Fracture Toughness of Anisotropic Rocks by Boundary Element Method

Summary  This paper presents a systematic procedure for determining fracture toughness of an anisotropic marble using the diametral compression test (Brazilian test) with a central crack on the discs. Additionally, a novel formulation to increase the accuracy in Stress Intensity Factor (SIF) calculations using Boundary Element Method (BEM) is applied to determine the stress intensity factors and the fracture toughness of anisotropic rocks under mixed-mode loading. The numerical results show that the SIFs for both isotropic and anisotropic problems are in good agreement with those reported by previous authors. The marble with clear white-black foliation from Hualien (in eastern Taiwan), was selected for the Brazilian tests. Diametral loading was conducted on the Cracked Straight Through Brazilian Disc (CSTBD) specimens to evaluate their fracture toughness. In addition, a new fracture criterion was developed to predict pure mode I, pure mode II or mixed mode (I–II) fracture toughness of the anisotropic marble. The new fracture criterion is based on the examination of mode I, mode II and mixed mode (I–II) fracture toughness for different crack angles and anisotropic orientation. Authors’ address: Associate Professor Chao-Shi Chen, Department of Resources Engineering, National Cheng Kung University, No. 1 Dasyue Rd., East District, Tainan 701, Taiwan     

Application of Cracked Triangular Specimen Subjected to Three-Point Bending for Investigating Fracture Behavior of Rock Materials

Numerical and experimental studies were performed on a new fracture test configuration called the edge cracked triangular (ECT) specimen. Using several finite-element analyses, the fracture parameters (i.e., K _I, K _II, and T-stress) were obtained for different combinations of modes I and II. The finite-element results show that the ECT specimen is able to provide pure mode I, pure mode II, and any mixed-mode loading conditions in between. Also, a series of mixed-mode fracture experiments were conducted on Neiriz marble rock using the proposed specimen. Furthermore, the generalized maximum tangential stress (GMTS) criterion was used to predict the experimental results. The GMTS criterion makes use of a three-parameter model (based on K _I, K _II, and T) for describing the crack tip stresses. Due to the significant positive T-stresses that exist in the ECT specimen, typical minimum fracture toughness values were expected to be obtained when the ECT specimen is used. The direction of fracture initiation and the path of fracture growth were also obtained theoretically using the GMTS criterion, and good agreement was observed between the experimental fracture path and theoretical simulations. The fracture study of this specimen reveals that the ECT specimen can be also used in mixed-mode fracture studies of rock materials in addition to the conventional circular or rectangular beam test samples.     

古构造应力场数值模拟方法探讨——以山西省晋城成庄煤矿区为例

从构造模拟目标、构造模型建立、构造模拟三个方面探讨了古构造应力场数值模拟的方法。以山西省晋城成庄煤矿区为例, 根据野外调查和微观构造形迹, 建立平面应力模型和三维地质模型, 确定岩体力学参数、边界条件及岩石破裂准则, 采用大型数值模拟软件ANSYS和FLAC计算, 确定外力的大小及加载顺序。通过分析研究, 揭示了山西晋城成庄煤矿区历史上曾发生先东西向、后南北向的两期大的构造运动, 加载外力为先东西向加载60 MPa, 再南北向加载110~180 MPa, 这个结果能解释多数地表剪节理和3#煤中剪节理同时发生。该分析对矿区的危险性分区及瓦斯突出区的预测具有重要的意义。      

Finite element modeling of hydraulic fracturing in 3D

A procedure based on the finite element method is suggested for modeling of 3D hydraulic fracturing in the subsurface. The proposed formulation partitions the stress field into the initial stress state and an additional stress state caused by pressure buildup. The additional stress is obtained as a solution of the Biot equations for coupled fluid flow and deformations in the rock. The fluid flow in the fracture is represented on a regular finite element grid by means of “fracture” porosity, which is the volume fraction of the fracture. The use of the fracture porosity allows for a uniform finite element formulation for the fracture and the rock, both with respect to fluid pressure and displacement. It is demonstrated how the fracture aperture is obtained from the displacement field. The model has a fracture criterion by means of a strain limit in each element. It is shown how this criterion scales with the element size. Fracturing becomes an intermittent process, and each event is followed by a pressure drop. A procedure is suggested for the computation of the pressure drop. Two examples of hydraulic fracturing are given, when the pressure buildup is from fluid injection by a well. One case is of a homogeneous rock, and the other case is an inhomogeneous rock. The fracture geometry, well pressure, new fracture area, and elastic energy released in each event are computed. The fracture geometry is three orthogonal fracture planes in the homogeneous case, and it is a branched fracture in the inhomogeneous case.     

Simulation of hydraulic fracture propagation near a natural fracture using virtual multidimensional internal bonds

A virtual multidimensional internal bond (VMIB) model developed to simulate the propagation of hydraulic fractures using the finite‐element method is formulated within the framework of the virtual internal bond theory (VIB) that considers a solid as randomized material particles in the micro scale, and derives the macro constitutive relation from the cohesive law between the material particles with an implicit fracture criterion. Hydraulic pressure is applied using a new scheme that enables simulation of hydraulically driven cracks. When the model is applied to study hydraulic fracture propagation in the presence of a natural fracture, the results show the method to be very effective. It shows that although the in situ stress ratio is the dominant factor governing the propagation direction, a natural fault can also strongly influence the hydraulic fracture behavior. This influence is conditioned by the shear stiffness of the fault and the distance to the original hydraulic fracture. The model results show that when the fault is strong in shear, its impact on hydraulic fracture trajectory is weak and the hydraulic fracture will likely penetrate the fault. For a weak fault, however, the fracture tends to be arrested at the natural fault. The distance between the fault and the hydraulic fracture is also important; the fault influence increases with decreasing distance. The VMIB does not require selection of a fracture criterion and remeshing when the fracture propagates. Therefore, it is advantageous for modeling fracture initiation and propagation in naturally fractured rock. Copyright © 2010 John Wiley & Sons, Ltd.     

三向应力下土体水力劈裂的破坏机理及适用性探讨

土体中的水力劈裂破坏机理存在两种观点：张拉破坏机理和剪切破坏机理。前人已经对其进行了大量地研究,并分别基于两种破坏机理提出了起劈压力的理论计算式,但是对其适用性没有进一步探讨。分别分析三向应力状态下土体水力劈裂的张拉破坏和剪切破坏判定准则,并基于Mohr-Coulomb屈服准则分析两种破坏机理的适用条件。分析结果表明,土体的水力劈裂是张拉破坏还是剪切破坏与小主应力σ3和不排水抗剪强度cu的大小密切相关,当小主应力σ3较大且不排水抗剪强度cu较小时,土体的劈裂多受剪切破坏机理控制;反之,土体的劈裂为张拉破坏。最后通过已有文献中的试验结果验证了所提出的两种破坏机理适用条件的合理性。     

考虑覆岩原生裂隙的导水裂隙带模拟

导水裂隙带高度的确定对松散承压含水层下煤矿安全开采和矿区生态环境保护具有重要意义。以往根据塑性区判断导水裂隙带范围的数值模拟方法不能完全反映覆岩的破断机制。为了更准确地预测导水裂隙带发育高度,应用断裂力学方法,将裂纹尖端K场区内的应力强度因子断裂判据与摩尔-库伦屈服准则结合,提出了原生裂隙存在时的岩石断裂准则。利用自仿射分形模型建立起原生裂隙场分布,并通过有限元分析软件COMSOL Multiphysics将原生裂隙场和岩石断裂准则应用到导水裂隙带发育的数值模拟中,对淮北煤田青东煤矿的839工作面开采进行了模拟计算。结果显示,考虑原生裂隙时,导水裂隙带在贯通后高度达到92.5 m。与传统数值模拟和经验公式法相比,考虑原生裂隙的模拟结果与现场测量结果更为接近。这说明,采用自仿射分形模型所生成的裂隙场可以较好地模拟岩体内复杂而无序的原生裂隙分布,且与传统数值模拟和经验公式法相比,考虑原生裂隙的模拟方法能够更好地反映导水裂隙带的发育规律。      

岩土力学试验中的两个问题讨论及其应用

本文根据实验和理论分析, 提出一种单轴、三轴压缩试验的新的破坏判据, 分析其机理是体积或密度连续原则的破坏。指出这一判据有可能应用在这种试验的自动控制上。     

水力裂缝穿越非连续面扩展时的断裂过程研究

非连续面发育是非常规油气储层的显著地质特征之一,水力裂缝能否穿越非连续面扩展会关系到压裂的改造效果。为研究水力裂缝穿越非连续面扩展时断裂过程区（fracture process zone,简称FPZ）发育特征,采用自主设计的可视化压裂试验装置对含预制摩擦界面的砂岩平板试件开展水力压裂试验。基于数字图像相关法实时监测了水力裂缝正交穿越界面扩展过程中的位移及应变场特征。试验结果表明,水力裂缝穿越界面扩展之前,断裂过程区已经开始跨越界面发育;裂缝能否穿越界面扩展在FPZ的初始发育阶段已经注定,不受FPZ内应力软化过程影响。基于Renshaw-Pollard准则建立了考虑FPZ边界范围的裂缝穿越非连续面扩展准则,并通过前人及文中试验数据进行了可靠性验证。相比而言,改进准则更准确地考虑了裂缝前端线弹性断裂力学的适用范围。研究发现FPZ长宽比对裂缝穿越界面扩展准则有显著影响,相同条件下,FPZ长宽比越大,裂缝正交穿越界面扩展所需要的摩擦系数下限值越小。