Theory of Three-Dimensional Discontinuous Deformation Analysis and Its Application to a Slope Toppling at Amatoribashi, Japan

A three-dimensional (3D) rock slope toppling occurred in a discontinuous rock mass. To simulate the failure process and study the mechanism of this rock failure with contact and large displacement in 3D, a new discrete numerical method has been developed called the 3D discontinuous deformation analysis (DDA). This article first introduces the basic principles and then derives the formulas in detail. Finally, the slope failure simulation is applied as an example to investigate the applicability of this new method to rock slope failure research. The simulation results indicate the advantages of using this new method to study the mechanism of a rock slope failure with 3D behavior.     

冲击荷载下岩石裂纹扩展研究进展

为了给深部资源开采和大型地下空间工程中围岩体的变形机理及稳定性控制提供理论基础,通过查阅大量关于表征岩石裂纹扩展的裂纹扩展模型、应力强度因子和断裂韧性的国内外文献,总结了前人的研究成果。依据现有研究,提出了动荷载作用下岩石裂纹扩展的几点建议：（1）综合考虑弹性力学、断裂力学和损伤力学建立岩石材料从微观断裂到宏观破坏这一演变过程的理论模型,使理论模型更加适应岩石材料的非线性特征;（2）采用分形、自组织和混沌等非线性理论表征动荷载作用下岩石内部以及表面裂纹的扩展演化特征;（3）采用颗粒离散元和有限差分模拟岩石材料裂纹扩展演化特征。     

Composite Element Analysis of Gravity Dam on a Complicated Rock Foundation

This paper presents the formulation and application of a composite element method, which is intended for numerical modeling of discontinuous rock masses. This method allows analysis of fractured rock masses using regular meshes that do not need to rigorously respect the orientations and positions of discontinuities. It can be incorporated in conventional finite-element programs. The performance of this method are illustrated through its use for the analysis of the mechanical behavior of the Baozhusi gravity dam which is constructed on a complex rock foundation.     

一种块体–颗粒–杆件的耦合方法及其在隧道支护模拟中的应用

为了模拟隧道开挖过程中边帮的失稳垮塌过程以及锚杆对隧道的支护过程,提出了一种基于罚弹簧的块体–颗粒–杆件的耦合方法.该耦合方法基于连续–非连续的数值模拟方法(CDEM),采用离散颗粒簇表征隧道周边松动圈以内的破碎岩体,采用块体单元表征松动圈以外的完整岩体,采用杆件单元描述锚杆及锚索等杆系类支护结构,采用插值耦合的方式实现杆件单元与离散颗粒及块体单元间力与位移的传递,从而实现高应力环境下隧道开挖失稳过程的模拟及支护效果的评价.颗粒与块体之间采用1根法向线性弹簧及2根切向线性弹簧进行耦合,法向弹簧引入拉伸断裂本构,切向弹簧引入Mohr–Coulomb脆性断裂本构.杆件与颗粒及杆件与块体之间的耦合模式基本一致,包含1根沿着杆件轴向的罚弹簧S_gn及1根垂直于杆件轴向的罚弹簧S_gs,S_gn主要用于描述杆件与围岩之间的拉拔效应及推压效应,S_gs则主要用于描述杆件与围岩之间的侧向挤压效应.圆形盾构隧道弹性场分析、预应力锚杆加固矩形巷道模拟、全长连接锚杆对岩块的锚固作用分析、以及碎裂岩体中的隧道开挖支护效果分析等案...     

On the effect of discontinuous decomposition on the structure and properties of high-nitrogen steels and on methods for suppression thereof

The features of discontinuous decomposition in high-nitrogen austentitic steels are considered. Structure and formation kinetics of pearlite-like colonies of “the austenite-with-equilibrium-nitrogen-content – Cr(M)₂N nitride” are discussed. The discontinuous decomposition of nitrogen supersaturated austenite is shown to effect harmfully the mechanical properties of the steels studied. To suppress the harmful effect of the discontinuous decomposition of the austenite the four methods are proposed as follows: use of vanadium as an alloying element, high-temperature thermomechanical treatment, production of a “microduplex” type structure and granule technology.     

Numerical Study of Scale Effects on the Stiffness Modulus of Rock Masses

The purpose of this paper is to contribute to the study of scale effects on the stiffness modulus of discontinuous rock masses from a mechanical point of view. The study has been conducted on the basis of the observation that the length and density of the natural discontinuities (cracks) in rock masses increase with the volume of the mass. Compressive tests on specimens containing open and closed flat cracks have been simulated through a numerical procedure that is based on the displacement discontinuity method and the fictitious stress method. Cracks have been generated, through a random process, with dips in the 0°–180° range. Both open and closed cracks have been considered. The numerical results obtained for specimens containing open cracks are found to approach the values obtained through an analytical solution. Then, the numerical method has been applied to the study of scale effects on the stiffness modulus of specimens with closed cracks. The numerical results show a decrease in the stiffness modulus with an increase in the size of the rock volume.     

Space-Time Discontinuous Galerkin Method for Linear Elastodynamics

Among the time-integration methods used in solid mechanics, Newmark family of algorithms (along with Galerkin finite element) has been most popular and has gathered much attention over the years. Recently, the time discontinuous Galerkin method (TDG) and discontinuous Galerkin method (DGM) are being investigated by the researchers due to their advantages in wave propagation problems. In this study, TDG and DGM are combined to have space-time discontinuous Galerkin formulation for the first time for solid mechanics problems. The basic formulations are presented and some examples are studied.     

Characterization of Strength and Deformation of Jointed Rock Mass Based on Statistical Analysis

This paper deals with the statistical analysis of the uniaxial compressive strength and of the elastic modulus of jointed rock masses under different confining pressures. Properties of the rock masses with different joint fabric, with and without gouge have been considered in the analysis. A large amount of experimental data of jointed rock masses from the literature has been compiled and used for this statistical analysis. The uniaxial compressive strength of a rock mass has been represented in a nondimensional form as the ratio of the compressive strength of the jointed rock to the intact rock. In the case of the elastic modulus, the ratio of elastic modulus of jointed rock to that of intact rock at different confining pressures is used in the analysis. The effect of the joints in the rock mass is taken into account by a joint factor. The joint factor is defined as a function of joint frequency, joint orientation, and joint strength. Several empirical relationships between the strength and deformation properties of jointed rock and the joint factor have been arrived at via statistical analysis of the experimental data. A comparative study of these relationships is presented. The effect of confining pressure on the elastic modulus of the jointed rock mass is also considered in the analysis. These empirical relationships are incorporated in a nonlinear FEM code to carryout the equivalent continuum analysis of jointed rock masses. The method presented in this paper recognizes that the jointed rock mass will act both as an elastic material and a discontinuous mass. The results obtained by the model with equivalent properties of the jointed rock mass predict fairly well the behavior of jointed rock mass.     

Kinematics of Overhanging Slopes in Discontinuous Rock

The kinematics of overhanging rock slopes and the mechanical constraints associated with this specific slope geometry were studied. Investigation of the problem began with a generalized rigid body analysis and was followed by a numerical discontinuous deformation analysis, both of which were performed in two dimensions. It was found that eccentric loading and hence the development of tensile stresses at the base of overhanging rock slopes control their stability. Global slope instability, which is typically manifested in a forward rotation failure mode, may ensue if a through-going vertical discontinuity, typically referred to as “tension crack,” transects the slope at the back. The transition from stable to unstable configurations depends on the distance between the tension crack and the toe of the slope. On the basis of the analysis, a simple threefold stability classification—stable, conditionally stable, and unstable—is proposed. In addition, geometrical guidelines, based on standard field mapping data, for the above stability classification are provided. Finally, the optimal reinforcement strategy for overhanging slopes is explored. The stability of overhanging slopes is determined by their eccentricity ratio, defined by the ratio between the base (B) and top (L) lengths: er = B/L. It was found that an overhanging slope with eccentricity ratio of er<0.38 is unstable and requires reinforcement. With an eccentricity ratio between 0.38相似文献   

急倾斜中厚不稳固矿体开采方法的研究

本文论述了急倾斜中厚不稳固矿体的开采方法.着重介绍了近年来在龙山金矿研究的成果——双向长锚索预控上盘分段留矿法.该法具有作业安全,成本低,工效高,贫化损失少的优点.在技术上首次试验了垂直加平行的长锚索预控上盘的方法,将不稳固的上盘围岩形成整体 结构独特,效果显著.其中平行上盘岩表层的长锚索有如钢筋混凝土板梁中的受力钢筋,大大提高了上盘围岩的抗弯强度,超出了一般长锚索的作用.此种加固围岩的办法可推广到某些其它的采矿方法中来控制不稳固的围岩.     

我国锰矿地压的基本问题与解决途径

以缓倾薄层锰矿床的地层特征，原岩应力等的基础，简述了锰矿床开采技术特征，采矿方法及相应地压活动规律与现状，针对花垣，遵义，鹤庆，斗南等锰矿山由房柱法开采年引起的地压隐患，提出了相应的原则与方法。     

钻井水溶法开采矿区地表移动随机介质理论预计研究

钻井水溶法开采流程简单、操作方便、劳动负荷轻、投资少、见效快，是一种很有发展前途的采矿方法。钻井水溶法开采形成的地下采空区可能会使地表发生移动和变形。随机介质预计理论概率积分法是建立在上履岩层软弱、顶板跨落基础上的非连续介质理论。由于沉积成矿的特点，岩盐矿床的地质条件决定了其岩石力学性质整体表现为顶、底板强度较低，适应于采用随机介质理论预计地表移动与变形。文章结合某钻井水溶法开采矿山实例，探讨地表移动与变形预计随机介质预计方法。     

钻井水溶法开采矿区地表移动随机介质理论预计研究

钻井水溶法开采流程简单、操作方便、劳动负荷轻、投资少、见效快,是一种很有发展前途的采矿方法。钻井水溶法开采形成的地下采空区可能会使地表发生移动和变形。随机介质预计理论概率积分法是建立在上覆岩层软弱、顶板跨落基础上的非连续介质理论。由于沉积成矿的特点,岩盐矿床的地质条件决定了其岩石力学性质整体表现为顶、底板强度较低,适应于采用随机介质理论预计地表移动与变形。文章结合某钻井水溶法开采矿山实例,探讨地表移动与变形预计随机介质预计方法。     

基于块体化程度和物元可拓理论的顶板稳定性分级方法及应用

基于块体化程度和物元可拓理论,提出一种适用于顶板稳定性分级的BET法(classification method based on blockiness and extension theory).从三维空间上运用块体化程度指标刻化顶板围岩的完整性,建立以块体化程度、单轴抗压强度、节理条件和地下水条件为指标的评价体系;构建物元可拓模型的经典域、节域和待评物元,分析指标间不相容问题,用可拓层次分析法计算指标权重;综合计算关联度,制定出稳定性分级方法与标准.选取广西铜坑矿四个裂隙岩体试验区,进行BET分级法的工程应用研究.将BET法分级结果分别与RMR法、RSR法、Q法等传统方法及BT法的结果进行了对比.结果表明:与其他各类分级方法相比,BET法所选指标体系更全面,评价方法更客观、科学,评价结果更准确.      

采矿方法研究与室内试验

复杂矿床开采技术条件的采矿方法研究，往往需要进行相应的室内试驻。本文对采矿方法研究与室内试验的有关问题进行初步探讨，以促进岩金矿山采矿方法研究取得更丰硕的科研成果。     

结构面岩体爆破破坏机理探究

岩体多属于各向异性的复杂不连续体。岩体中主要结构面在爆破时,会对岩石的破坏和最终的爆破效果产生影响。总结了结构面岩体爆破破坏机理的研究现状,并从应力波传播、岩体破坏方式等方面研究了结构面岩体爆破的影响。在研究结构面岩体爆破破坏作用机理的基础上,提出改善爆破效果的技术措施,供同类型矿山参考。