岩石破裂过程分析系统并行计算方法研究

岩石工程灾害与岩石破裂过程失稳密切相关。大型岩石工程破裂过程数值分析需要高效、准确、强大的计算能力支持。一般传统串行计算方法难以满足要求，大规模并行计算是解决这一难题的有效途径。岩石破裂过程分析系统是研究岩石破裂过程的一个重要数值分析工具。代有限元方法和数值计算方法，在消息传递并行环境下，在岩石破裂过程分析系统串行单机版的基础上，结合现利用区域分解和主从编程模式，采用分布存储稀疏线性迭代并行求解方法，在Linux机群上实现应力分析模块中有限元计算的并行处理。通过Windows和Linux协调处理策略，有效地把原有的前后处理功能和机群系统强大的计算能力结合起来，建立岩石破裂过程分析RFPA^3D．Parallel并行分析系统。算例结果表明，并行程序具有很高的加速比和并行效率，能够快速完成三维条件下300万单元的大规模岩石破裂过程分析。应用RFPA^3D-Parallel并行分析系统模拟地壳介质中广泛存在的龟裂现象，再现非均匀介质破坏和裂纹演化过程，从而显示该系统广泛的应用前景。     

岩石三维破裂过程的数值模拟研究

采用细观弹性损伤模型和有限元计算方法实现岩石三维破裂过程的数值模拟。考虑到岩石非均匀性的本质特征，通过引入简单直观的单元本构模型，采用细观单元材料性质退化的办法，利用位移加载来实现岩石逐渐破裂过干旱；模拟单轴压缩、单轴拉伸和剪切破裂3种基本试验，得到岩石非线性应力-应变曲线和不同载荷阶段三维损伤破裂演化系列图像；分析细观非均匀性对岩石宏观破裂力学行为的影响。试验研究表明，三维破裂比二维破裂更为复杂，RFPA^3D可以有效地模拟脆性材料的三维破裂。     

一种广义节理元模型

采用传统节理元近似模拟岩石破坏过程需要同时增加单元和节点,过程非常复杂。为了更有效模拟岩石岩石破坏过程产生的节理,建议了一种只包含2个节点的广义节理元的模拟方法,通过推导给出了基本方程,提供了单元信息设置方式。采用该广义节理元近似模拟岩石破坏过程只需要增加单元,不需要增加节点。模拟实例表明：采用广义节理元法模拟效果在应力方面精度和传统节理元法的精度一样,该广义节理元法有效可行。     

循环载荷作用下岩石单轴压缩破坏过程的平面弹塑性细胞自动机模型

采用平面弹塑性细胞自动机模型在细观尺度上模拟应变软化岩石类材料的单轴压缩破坏过程。在平面弹性力学细胞自动机的基础上,推导分析平面弹塑性问题的细胞自动机更新规则,开发二维岩石弹塑性细胞自动机数值模拟软件;模拟不同均质度岩石的单轴压缩破坏过程,并在应力峰值后区考虑反复加卸载过程。模拟得到的岩石单轴压缩条件下的全程应力-应变曲线与典型的加卸载应力-应变试验曲线吻合较好,模拟得到的声发射曲线很好地反映出岩石声发射的Kaiser效应。     

Limit analysis solutions for the bearing capacity of rock masses using the generalised Hoek–Brown criterion

This paper applies numerical limit analyses to evaluate the ultimate bearing capacity of a surface footing resting on a rock mass whose strength can be described by the generalised Hoek–Brown failure criterion [Hoek E, Carranza-Torres C, Corkum B. Hoek–Brown failure criterion—2002 edition. In: Proceedings of the North American rock mechanics society meeting in Toronto, 2002]. This criterion is applicable to intact rock or heavily jointed rock masses that can be considered homogeneous and isotropic. Rigorous bounds on the ultimate bearing capacity are obtained by employing finite elements in conjunction with the upper and lower bound limit theorems of classical plasticity. Results from the limit theorems are found to bracket the true collapse load to within approximately 2%, and have been presented in the form of bearing capacity factors for a range of material properties. Where possible, a comparison is made between existing numerical analyses, empirical and semi-empirical solutions.     

浅埋软土隧道蠕变问题的有限元分析

应用基于遗传蠕变理论的幂次关系蠕变方程,对浅埋软土隧道施工过程进行了二维粘弹塑性有限元分析。研究了隧道施工时围岩主应力、地表沉降、及支护结构内力随时间的变化规律,并与按弹塑性理论计算结果进行比较,说明了对软土区间隧道施工过程模拟中考虑土体蠕变特性的必要性。     

大理岩破坏过程的三维细观弹塑性损伤模拟研究

为了考虑岩石细观局部塑性变形,基于应变空间理论导出细观弹塑性损伤模型,采用有限元计算方法实现岩石三维破裂过程的数值模拟。提出细观破坏单元网格消去法,利用位移加载来实现岩石逐渐破裂过程;模拟二维、三维大理岩三点弯曲梁弹塑性损伤破坏试验,得到岩石非线性应力–应变曲线和不同载荷阶段弹塑性损伤破裂演化系列图像;分析细观非均匀性对岩石宏观破裂力学行为的影响。试验研究表明,三维破裂比二维破裂更为复杂,本文所建模型可以有效地模拟岩体的三维破坏过程。     

Modeling impact in down-the-hole rock drilling

In this work a study of impact in Down-the-Hole (DTH) rock drilling is carried out. We present an alternative to a method previously introduced by Lundberg and his co-workers. Our model is formulated in terms of the impulse–momentum principle while Lundberg’s method is based in solving the one-dimensional wave equation. In the case of DTH drilling, the study of the subject becomes easier because the handling of many bodies interacting dynamically is simplified, and different boundary conditions, such as constant body forces, distributed forces and initial strains, can be directly included. The rock–bit interaction is modeled using both a non-linear spring and a variable gap using experimental parameter data obtained by other researchers and by a normalized quasi-static penetration test described in this work. The simulation results are in good agreement with results in previous publications as well as with experimental validation measurements carried out by the authors.     

基于零厚度黏聚力单元节理面剪切破坏机理宏细观研究

为了探究不同粗糙度节理岩体剪切过程及破坏类型,利用ABAQUS有限元分析软件,采用全局嵌入零厚度黏聚力单元的方法模拟带节理岩体压剪过程。通过室内压剪试验和数值模拟结果对比确定所建立模型的正确性,从宏细观角度分析节理岩体剪切破坏行为。研究结果表明：采取全局嵌入零厚度黏聚力单元模拟节理岩体压剪过程的方法相对准确,能真实反映节理面细观破坏过程;不同粗糙度节理试样在恒定法向荷载下的剪切峰值强度随着粗糙度增加而递增;节理岩体的剪切过程大致可以分为4个阶段,线弹性强化阶段、带裂纹强化阶段、塑性软化阶段和残余强度阶段;不同粗糙度节理岩体在剪切过程中破坏类型不同,在恒定法向荷载下岩体剪切破坏大致可以分为3种形式,分别是滑移破坏,岩体局部剪断破坏和切齿破坏。     

2D and 3D finite element analysis of underground openings in an inhomogeneous rock mass

The finite element analysis of the underground openings excavated for Koyna hydroelectric project, Maharashtra, India, has been conducted. 2D and 3D models have been developed assuming that the rock mass obeys Drucker–Prager failure criterion. The computed deformations and the stress distribution, around these openings, have been compared with the in situ measurements. The study reveals that the 2D elasto-plastic analysis underestimates the deformations. On the other hand, the 3D elasto-plastic analysis yields results, which compare reasonably well with the in situ measurements. The effect of weak zones in the rock mass and creation of multiple cavities in the nonhomogeneous rock mass has also been considered in the analyses. Such a study is found to be very helpful for evaluating the stability of underground openings when extensive realistic input data is available for nonhomogeneous rock mass.     

节理岩体裂隙扩展过程一种新改进的弹脆性模拟方法及应用

 通过改进原有的FLAC3D本构关系为弹脆性本构,并采用超细单元划分法,模拟和研究双裂隙岩石试件在单轴、双轴加载作用下的破坏过程。数值计算结果与前人试验所得到的相应结果具有良好的一致性。用此方法还模拟了4条2组不同倾向裂隙的破裂过程和椭圆形三维单裂隙的扩展过程,且三维数值模拟结果与前人试验也有很好一致性。最后,将该模型引入到某边坡开挖工程的裂隙扩展过程研究和稳定性分析中,取得较好效果。     

Rock mass—mine workings interaction model for Polish copper mine conditions

Geological and mining conditions characteristic for the Polish Legnicko–Glogowski Okreg Miedziowy (LGOM) copper mines as well as various exploitation systems utilized in that area are presented. The historical background of mining systems development as well as their classification are also reviewed.Presently, due to difficult mining conditions, a new more universal analytical tool for mine workings geometry selection is required. Therefore, a very useful in design process multi-plate analogy based physical model of rock mass—mine workings interaction has been developed and presented in the paper. The model utilizes the analytical approximation of pillar compression including the effect of pillar critical and residual strength on roof strata deflection resulting in the definite bump hazard level.The research performed in the past which dealt with the effect of size and slenderness on pillar strength is reviewed. A new approach for pillar strength calculation and its utilizing in a general problem of overburden–mine workings interaction is proposed. The problem has been illustrated by numerical examples concerning a rock mass static and dynamic behavior in the area of one of the underground Polish copper mines. By solving the numerical model based on the finite element method formulated in three dimensions, the effect of extraction path on mine workings safety in a static load domain has been proved. The dynamic load transfer from mine workings to a shaft lining has also been determined.     

冲击机械活塞强度研究的现状

在查阅大量文献的基础上,对凿岩机、冲击器等冲击机械的活塞应力与强度研究现状进行了分析,总结出目前的研究主要有应用一维波动力学理论对冲击机械的活塞进行强度分析、应用有限元软件对冲击机械活塞进行强度分析、分析活塞失效机理,从设计选材及热处理方面提高活塞强度的方法三种类型。     

A new model for effects of impersistent joint sets on rock slope stability

Joints often have profound effects on elastic properties and strength of rock masses and therefore on rock slope stability. In surface mine slopes, joints are usually too numerous to be taken into account individually, so an equivalent properties approach is necessary. Previous work that treats a jointed rock mass as an equivalent composite material of joints and intact rock between resulted in excellent agreement between estimated and true rock mass elastic moduli in case of fully persistent joints, for example, [Pariseau WG. An equivalent plasticity theory for jointed rock masses. Int J Rock Mech Min Sci 1999;36(7):907–18]. Rock mass failure mechanisms on joints and through intact rock were retained using influence functions obviating the need for an equivalent rock mass strength. Impersistent joints, which are not continuous on a joint plane, can be accommodated [Pariseau WG. Effects of joint persistence on jointed rock masses. Trans Soc Min Metal Explor 2003;314:121–8]. However, slope stability analysis of a large, deep copper mine indicated a need for computational efficiency even in two-dimensional analysis of vertical sections through pit walls [Puri S. Role of joint persistence in rock slope stability. MS thesis, Department of Mining Engineering, University of Utah, 2006]. The analyses by the popular finite element method used small elements of bench size near the pit slopes and much larger elements away from the pit walls. The reasons for the graded meshes were numerical accuracy (small elements) and computational economy (large elements). Small elements contained only a few joints, while the larger elements contained hundreds of joints and led to impractical computation run times, on the order of days. A new modeling procedure that recognizes sufficiently large elements as representative volume elements (RVEs) assists in overcoming this obstacle. A companion improvement embeds a sufficient number of joints in RVE-size elements that then allows for recovery of joint failure mechanisms that are lost with the RVE designation. These innovations reduced PC (Pentium-4) run times by two orders of magnitude to a few hours.     

岩石破裂过程分析(RFPA2D)系统的细观单元本构关系及验证

从岩石的细观非均匀性特点出发，应用弹性损伤力学，对岩石破裂过程分析数值（RFPA^2D)模拟系统的本构关系进行了描述。用RFPA^2D系统模拟了岩石试样在单轴或双轴载荷作用下的强度特征和破坏形态，通过与实验结果对比验证了该本构关系和数值模拟系统的合理性和有效性。     

岩石单轴拉伸破坏过程的数值模拟

用三维梁–颗粒模型BPM3D(Beam-Particle Model in Three Dimensions)对岩石材料在单轴拉伸条件下的力学性质和破坏过程进行了数值模拟。梁–颗粒模型是在离散单元法基础上,结合有限单元法中的网格模型提出的用于模拟岩石类材料损伤破坏过程的数值模型。模型中材料在细观层次上被离散为颗粒单元集合体,相邻颗粒单元由有限单元法中的弹脆性梁单元联结。梁单元的力学性质按韦伯(Weibull)分布随机赋值,以模拟岩石材料力学参数的空间变异性。材料内部裂纹通过断开梁单元来模拟。通过自动生成的非均质材料模型对岩石材料的破坏机理进行研究。岩石在单轴拉伸状态下破坏过程细观数值模拟结果显示,岩石材料宏观破坏是由于其内部细观裂纹产生、扩展、连接的结果。数值模拟结果与实验结果的对比分析表明了模型的适用性。根据数值模拟结果对岩石材料的破坏机理进行了探讨。     

高预应力让压锚杆数值模拟方法研究

建议了一种考虑高预应力让压锚杆锚芯与岩石间剪切破坏作用的三维锚杆计算模型,并开发了相应的有限元程序。由于采用2节点三维杆件单元和4节点三维锚杆单元模拟高预应力让压锚杆,使得所建议的模拟方法适用范围更加广泛,可以用于锚索模拟、一般锚杆模拟和抗滑桩等桩结构模拟,且能够很好地模拟高预应力让压锚杆的力学特性。     

大理岩三点弯曲梁弹塑性损伤破坏研究

在应变空间内,推导出弹塑性损伤增量本构方程,通过自编程序实现该本构方程,同时将此程序实现了并行算法;建立了三点弯曲梁二维及三维细观尺度数值试样,分别进行相应地弹塑性损伤破坏数值模拟,作了相应的对比分析,在数值模拟中,提出破坏单元网格消去法,模拟裂纹扩展。研究发现:数值试验同物理试验较吻合,且与理论分析是一致的;由于三维试样细观单元的非线性比二维在空间上更为离散,由三维细观单元弹塑性损伤非线性反映宏观试样的非线性,更能深入地研究细观破坏机理;提出的破坏单元网格消去法为有限元清晰模拟裂纹开辟了新的途径;并行算法程序的实现为应用于大型三维水利水电工程奠定了基础。     

Linearization of the Hoek and Brown rock failure criterion for tunnelling in elasto-plastic rock masses

We present a novel methodology for estimation of equivalent Mohr–Coulomb strength parameters that can be used for design of supported tunnels in elasto-plastic rock masses satisfying the non-linear empirical Hoek–Brown failure criterion. We work with a general adimensional formulation of the Hoek–Brown failure criterion in the space of normalized Lambe's variables for plane stress, and we perform linearization considering the stress field in the plastic region around the tunnel. The procedure is validated using analytical solutions to a series of benchmark test cases. Numerical solutions are also employed to validate the procedure in cases for which analytical solutions are not available. Results indicate that the stress field in the plastic region around the tunnel, as well as the linearization method employed and the quality of the rock mass, has a significant impact on computed estimates of equivalent Mohr–Coulomb strength parameters. Results of numerical analyses also show that our proposed linearization method can be employed to estimate loads and moments on the tunnel support system. We recommend the equating model responses (EMR) method to compute equivalent Mohr–Coulomb strength parameters when the tunnel support pressure is accurately known, and we further show that our newly introduced linearization method can be employed as an alternative to the best fitting in the existing stress range (BFe) and best fitting in an artificial stress range (BFa) methods, providing performance estimates that are generally better than estimates of the BFe and BFa methods when differences with the response of the Hoek–Brown rock mass are of engineering significance (say more than 10%).