Rock brittleness indices and their applications to different fields of rock engineering:A review

Brittleness is an important parameter controlling the mechanical behavior and failure characteristics of rocks under loading and unloading conditions,such as fracability,cutability,drillability and rockburst proneness.As such,it is of high practical value to correctly evaluate rock brittleness.However,the definition and measurement method of rock brittleness have been very diverse and not yet been standardized.In this paper,the definitions of rock brittleness are firstly reviewed,and several representative definitions of rock brittleness are identified and briefly discussed.The development and role of rock brittleness in different fields of rock engineering are also studied.Eighty brittleness indices publicly available in rock mechanics literature are compiled,and the measurement method,applicability and limitations of some indices are discussed.The results show that(1)the large number of brittleness indices and brittleness definitions is attributed to the different foci on the rock behavior when it breaks;(2)indices developed in one field usually are not directly applicable to other fields;and(3)the term“brittleness”is sometimes misused,and many empirically-obtained brittleness indices,which lack theoretical basis,fail to truly reflect rock brittleness.On the basis of this review,three measurement methods are identified,i.e.(1)elastic deformation before fracture,(2)shape of post-peak stressestrain curves,and(3)methods based on fracture mechanics theory,which have the potential to be further refined and unified to become the standard measurement methods of rock brittleness.It is highly beneficial for the rock mechanics community to develop a robust definition of rock brittleness.This study will undoubtedly provide a comprehensive timely reference for selecting an appropriate brittleness index for their applications,and will also pave the way for the development of a standard definition and measurement method of rock brittleness in the long term.     

Challenges associated with numerical back analysis in rock mechanics

Numerical back analysis is a valuable tool available to rock mechanics researchers and practitioners. Recent studies related to back analysis methods focused primarily on applications of increasingly sophisticated optimization algorithms (primarily machine learning algorithms) to rock mechanics problems. These methods have typically been applied to relatively simple problems; however, more complex back analyses continue to be conducted primarily through ad hoc manual trial-and-error processes. This paper provides a review of the basic concepts and recent developments in the field of numerical back analysis for rock mechanics, as well as some discussion of the relationship between back analysis and more broadly established frameworks for numerical modelling. The challenges of flexible constraints, non-uniqueness, material model limitations, and disparate data sources are considered, and representative case studies are presented to illustrate their impacts on back analyses. The role of back analysis (or “model calibration”) in bonded particle modelling (BPM), bonded block modelling (BBM), and synthetic rock mass (SRM) modelling is also considered, and suggestions are made for further studies on this topic.     

A review of multi-criteria decision-making methods for infrastructure management

In infrastructure management, multi-criteria decision-making (MCDM) has emerged as a decision support tool to integrate various technical information and stakeholder values. Different MCDM techniques and tools have been developed. This paper presents a comprehensive review on the application of MCDM literature in the field of infrastructure management. Approximately 300 published papers were identified that report MCDM applications in the field of infrastructure management during 1980–2012. The reviewed papers are classified into application to the type of infrastructure (e.g. bridges and pipes), and prevalent decision or intervention (e.g. repair and rehabilitate). In addition, the papers were also classified according to MCDM methods used in the analysis. The paper provides taxonomy of those articles and identifies trends and new developments in MCDM methods. The results suggest that there is a significant growth in MCDM applications in infrastructure management applications of MCDM over the last decade. It has also been noted that many decision support tools based on multiple MCDM methods have been successfully used for infrastructure management.     

Yue’s solution of classical elasticity in n-layered solids: Part 1, mathematical formulation

This paper presents the exact and complete fundamental singular solutions for the boundary value problem of a n-layered elastic solid of either transverse isotropy or isotropy subject to body force vector at the interior of the solid. The layer number n is an arbitrary nonnegative integer. The mathematical theory of linear elasticity is one of the most classical field theories in mechanics and physics. It was developed and established by many well-known scientists and mathematicians over 200 years from 1638 to 1838. For more than 150 years from 1838 to present, one of the remaining key tasks in classical elasticity has been the mathematical derivation and formulation of exact solutions for various boundary value problems of interesting in science and engineering. However, exact solutions and/or fundamental singular solutions in closed form are still very limited in literature. The boundary-value problems of classical elasticity in n-layered and graded solids are also one of the classical problems challenging many researchers. Since 1984, the author has analytically and rigorously examined the solutions of such classical problems using the classical mathematical tools such as Fourier integral transforms. In particular, he has derived the exact and complete fundamental singular solutions for elasticity of either isotropic or transversely isotropic layered solids subject to concentrated loadings. The solutions in n-layered or graded solids can be calculated with any controlled accuracy in association with classical numerical integration techniques. Findings of this solution formulation are further used in the companion paper for mathematical verification of the solutions and further applications for exact and complete solutions of other problems in elasticity, elastodynamics, poroelasticty and thermoelasticity. The mathematical formulations and solutions have been named by other researchers as Yue’s approach, Yue’s treatment, Yue’s method and Yue’s solution.     

人工神经网络与遗传算法在岩石力学中的应用

岩石力学与岩石工程问题包含极其丰富的内容，实际工程问题又不断地提出各种新的要求，致使很多问题利用传统的方法难于解决。借鉴其他相关学科的先进思想与技术来解决岩石力学研究中的难点问题，已经成为当前岩石力学研究领域的一个热门课题。计算智能中有关模型与方法的利用有助于我们更深入地研究与解决岩石力学中的某些问题。参考近年来人工神经网络与遗传算法在岩石力学应用中的某些问题，对有关课题的研究状况与进展做了介绍，对计算智能在岩石力学与岩石工程中的应用研究做了展望。     

Space decomposition based parallelization solutions for the combinedfiniteediscrete element method in 2D

The combined finiteediscrete element method （FDEM） belongs to a family of methods of computationalmechanics of discontinua. The method is suitable for problems of discontinua, where particles aredeformable and can fracture or fragment. The applications of FDEM have spread over a number of disciplinesincluding rock mechanics, where problems like mining, mineral processing or rock blasting canbe solved by employing FDEM. In this work, a novel approach for the parallelization of two-dimensional（2D） FDEM aiming at clusters and desktop computers is developed. Dynamic domain decompositionbased parallelization solvers covering all aspects of FDEM have been developed. These have beenimplemented into the open source Y2D software package and have been tested on a PC cluster. Theoverall performance and scalability of the parallel code have been studied using numerical examples. Theresults obtained confirm the suitability of the parallel implementation for solving large scale problems.
2014 Institute of Rock and Soil Mechanics, Chinese Academy of Sciences. Production and hosting byElsevier B.V. All rights reserved.     

A review of the state of the art in modelling progressive mechanical breakdown and associated fluid flow in intact heterogeneous rocks

The purpose of this review is to present techniques, advances, problems, and new developments in modelling the progressive mechanical breakdown of, and associated fluid flow in, intact heterogeneous rock. In general, the theoretical approach to this physical process can be classified into the three categories of discrete models based on fracture mechanics, the continuum damage mechanics approach, and statistical approaches. This categorisation forms the skeleton of this article.Recognising that intact rock contains ubiquitous cracks and flaws between grains and particles of various shapes, fracture mechanics has been widely used to study the mechanical breakdown process in terms of the growth of these discrete defects. Two types of fracture mechanics models, namely open crack and sliding crack models, are used to simulate the progressive microfracturing of rock upon loading, and the application of these to modelling mechanical breakdown is discussed in Section 2.As an alternative to the explicit treatment of cracking given by fracture mechanics, continuum damage mechanics (CDM) takes a phenomenological route that considers the averaged effect of microstructural changes, and has found widespread use in simulating macroscopic stress–strain responses. Through the introduction of damage variables as state operators that quantify change in mechanical properties such as stiffness and strength with respect to damage, CDM models are capable of reproducing realistic hydro-mechanical responses during rock disintegration. This method is discussed in Section 3.Recognising that intact rock is never strictly an isotropic and homogeneous material, statistical approaches use, in general terms, statistical distributions as a means of describing the variation of material properties in natural rock. These approaches have enjoyed a great deal of attention in past decades. By employing different numerical schemes, three major statistical models have been developed: continuum-based damage mechanics models, particle models, and network/lattice models. The merits and drawbacks of these models are discussed in Section 4.Coupled deformation and pore fluid diffusion can be important in the process of progressive breakdown. This poromechanical effect involves the interaction between the solid constituents of, and the interstitial fluids in, heterogeneous rocks under those circumstances when mechanical perturbation occurs sufficiently rapidly that induced pore pressure changes cannot fully dissipate. The mechanisms and analytical approaches, and their development relevant to progressive mechanical breakdown and fluid-flow modelling, are outlined in Section 5.Finally, based on this review, remarks are made summarising the current progress of, and fundamental problems with, these developments. Ideas for further improvements towards more comprehensive and robust techniques are suggested.     

层状岩体边坡锚固的断裂力学原理

岩体边坡的锚固及稳定性问题是岩土工程中困难的问题之一,长期以来,岩体边坡锚固效果一直没有较好的计算方法。基于线弹性断裂力学原理,将层状岩体的层间潜在最弱面等效为等间距共线多节理的力学模型,通过分析含有一条节理的有限大小岩体在压剪应力作用下节理线附近应力场在锚固前后的变化,提出了计算由于锚固引起的锚固效果公式,较好地解释了边坡锚固的增效问题。     

Dynamic notched semi-circle bend(NSCB) method for measuring fracture properties of rocks:Fundamentals and applications

Rocks are increasingly used in extreme environments characterised by high loading rates and high confining pressures.Thus the fracture properties of rocks under dynamic loading and confinements are critical in various rock mechanics and rock engineering problems.Due to the transient nature of dynamic loading,the dynamic fracture tests of rocks are much more challenging than their static counterparts.Understanding the dynamic fracture behaviour of geomaterials relies significantly on suitable and reliable dynamic fracture testing methods.One of such methods is the notched semi-circle bend(NSCB) test combined with the advanced split Hopkinson pressure bar(SHPB) system,which has been recommended by the International Society for Rock Mechanics and Rock Engineering(ISRM) as the standard method for the determination of dynamic fracture toughness.The dynamic NSCB-SHPB method can provide detailed insights into dynamic fracture properties including initiation fracture toughness,fracture energy,propagation fracture toughness and fracture velocity.This review aims to fully describe the detailed principles and state-of-the-art applications of dynamic NSCB-SHPB techniques.The history and principles of dynamic NSCB-SHPB tests for rocks are outlined,and then the applications of dynanic NSCB-SHPB method(including the measurements of initiation and propagation fracture toughnesses and the limiting fracture velocity,the size effect and the digital image correlation(DIC) experiments) are discussed.Further,other applications of dynamic NSCB-SHPB techniques(i.e.the thermal,moisture and anisotropy effects on the dynamic fracture properties of geomaterials,and dynamic fracture toughness of geomaterials under pre-loading and hydrostatic pressures) are presented.     

Artificial Intelligence in Bridge Engineering

Abstract: The idea to use artificial intelligence (AI) in civil engineering is as old as AI itself. Since the 1950s, studies on AI applications in civil or bridge engineering have proliferated. Most of these studies have dealt with specialized isolated engineering subtasks. Few of the applications have been delivered to practitioners and were used to advance their work. This paper presents a model of the life-cycle flow of information in bridge engineering as an organizing framework for reviewing previous work on AI applications in bridge engineering. Several common patterns that emerge from the studies are summarized. A subsequent analysis of the status of the bridge stock in many countries suggests that a more integrated approach to AI applications may have a larger practical impact. Several practical areas that can benefit significantly from AI techniques are identified, and several studies are proposed including the AI technology needed and the methodology according to which these applications should be developed.     

国标《工程岩体分级标准》的应用与进展

 依据已发表的与《工程岩体分级标准》(GB50218-94)(简称《国标》)相关的各类文献成果的整理与分析,对《国标》执行以来的工程应用实践效果、《国标》与RMR,Q系统及HC法等分级方法的相关性、在行业标准制订上的推动作用、以及基于《国标》的研究方法进展及相关完善建议等进行总结和综述。基于多个工程200余组实测数据的统计分析,给出《国标》BQ值与RMR分值间的综合统计回归公式,对《国标》BQ法与RMR法级别划分的对应性进行验证。研究表明,该分级方法体系严谨,具有很强的科学性和可操作性。利用岩体基本质量指标BQ,减少分级的主观性,提高分级的精度,降低工作难度,方便不同设计阶段的工程应用。另一方面,在已有实践基础上,有必要对该分级方法作进一步的修订和完善。     

A review of mining-induced seismicity in China

Active seismicity and rockbursting have been an emerging problem in Chinese mines. The distribution and characteristics of mining-induced seismicity in China, and its monitoring, mitigation, and research, are reviewed in this paper. Mining at depth and the activity of current tectonic stress field are the two major factors leading to rockburst hazards. Three critical depths, i.e., critical initiation depth, roof upper-bound depth, and floor lower-bound depth, have been identified based on hypocenter data of seismic events in coalmines. A strong correlation between rockbursts and gas outbursts in coalmines has also been established, and it is recommended to use this correlation for rockburst and gas outburst hazard assessment and warning interchangeably. We find that the key problems of rockburst hazard mitigation in China are the lack of mine seismicity-monitoring networks in most mines, and the need for improvement of the accuracy of the monitoring systems for mines that have been equipped with such systems. Because the demand for minerals resources is extremely high and the mining activities are progressing deeper and deeper, an increasing trend of mining-induced seismicity hazards in China may be anticipated for the near future. Mining-induced seismicities are hazards, but at the same time they have been found useful for studying geophysical problems in deep ground, particularly in the field of earthquake prediction. With the enforcement of relevant laws for the mining industry and the continuous effort to study rockburst problems using rock mechanics and geophysics principles and methods, it is believed that new approaches for rockburst hazard control and mitigation can be developed.     

Computational methods for fracture in rock: a review and recent advances

We present an overview of the most popular state-of-the-art computational methods available for modelling fracture in rock. The summarized numerical methods can be classified into three categories: Continuum Based Methods, Discrete Crack Approaches, and Block-Based Methods. We will not only provide an extensive review of those methods which can be found elsewhere but particularly address their potential in modelling fracture in rock mechanics and geotechnical engineering. In this context, we will discuss their key applications, assumptions, and limitations. Furthermore, we also address ‘general’ difficulties that may arise for simulating fracture in rock and fractured rock. This review will conclude with some final remarks and future challenges.     

陈宗基讲座：岩石流变力学及其工程应用研究的若干进展

讨论岩石流变力学及其工程应用研究近年来的若干进展，主要内容包括：对岩石工程流变学问题的综述性介绍、软岩和节理裂隙发育岩体的流变试验研究、流变模型辨识与参数估计、流变力学手段在收敛约束法及隧道结构设计优化中的应用、高地应力隧洞围岩非线性流变及其对洞室衬护的力学效应，以及岩石流变损伤与断裂研究。此外，还对土力学与土工流变方面的一些进展作了简要介绍，并就今后岩土工程流变研究的展望阐述了一点认识。     

An application of fuzzy sets to the Diggability Index Rating Method for surface mine equipment selection

Assessment of the most appropriate excavation method and related equipment plays an important role in the mining and civil engineering projects. Therefore, accurate methods of estimating the ease of excavation are required. For the past three decades, various empirical predictive methods have been proposed by a number of authors. Of these, rock mass classification systems are one of the most common means of excavatability assessment. Such classification systems assign quantifiable values to selected geotechnical parameters of the rock mass. The resulting ratings are then related to ease of digging and equipment type. Despite their widespread use in practice, they have some common deficiencies leading to uncertainties in their practical applications. These deficiencies are particularly related with the existing sharp transitions between two adjacent excavation classes and the subjective uncertainties on data that are close to the range boundaries of rock classes.In this study, the basic principles of the fuzzy set theory were described and then the fuzzy set theory was applied to one of the conventional classification systems by following the Mamdani fuzzy algorithm. It was shown that the fuzzy set theory could effectively overcome the uncertainties encountered in the practical applications of conventional classification systems, and also provides more information on the obtained final ratings. To be able to check the performance of this approach in practice, case study data previously collected from operating surface mines were used. Finally, it was concluded that the fuzzy set theory could also be applied to other similar rock excavation classification schemes existing in the literature.     

地下水影响下裂隙岩质边坡变形的Fuzzy测度分析

根据裂隙岩质边坡工程实际,采用 Fuzzy 数学理论中的 Fuzzy 测度理论,将工程开挖引起裂隙岩质边坡移动变形这一客观现象视为一模糊事件,依此建立了在地下水影响下岩体移动变形预测分析的 Fuzzy 测度模型。利用该模型可对边坡岩体移动变形参数进行反分析,并可对边坡开挖过程中引起的岩体移动变形进行定量计算,进而对地下水影响下岩质边坡总体稳定性和稳定程度进行预测。对已有的矿山边坡岩体移动变形及其稳定性进行了具体的分析预测,结果符合工程实际。     

岩体结构面连通率研究进展及应用

岩体结构面连通率的研究一直是岩石力学研究领域的难点之一。一些学者已经相继提出了多种确定连通率的方法，但许多方法可能引起的误差较大，实用性也较差。广义H—H连通率公式和基于网络模拟的计算方法是近年发展起来的比较成熟且实用的方法。文章评述了各种方法的适用性和有效性，并采用基于结构面网络模拟的“带宽投影法”进行了实例分析，最后讨论了岩体结构面连通率的研究趋向。     

分形几何及其在岩土力学中的应用

本文介绍了分形几何的基本概念,并建议将其在实际问题中的分析和应用归结为三种方法。然后就分形几何在岩土材料孔隙的几何图形,岩石的破碎、损伤和断裂,以及岩石节理面的粗糙度等问题中的应用进行了详细的讨论,以说明分形几何为岩土材料的复杂力学问题的研究提供了一种崭新的有力工具。     

Hoek-Brown强度准则研究进展与应用综述

1980年E. Hoek和E. T. Brown提出了Hoek-Brown(H-B)强度准则,已充分得到岩石力学与工程研究者的认同,并进行研究和应用。首先系统地阐述H-B强度准则研究进展：E. Hoek和E. T. Brown对H-B强度准则的研究成果、三维H-B强度准则、H-B强度准则岩石和岩体参数研究、考虑层状节理的H-B强度准则及其参数的各向异性研究。再对过去30 a国内外基于H-B强度准则工程应用的成果进行总结。最后对笔者所开展的H-B强度准则最新研究工作进行介绍：提出一种真正意义上的广义三维H-B强度准则,并采用3种Lode角函数进行屈服面修正,使其可以直接应用于后续本构模型建立和数值软件嵌入;采用三维颗粒流模型进行微观数值建模,对H-B强度准则岩石和岩体参数开展微观研究并建立多尺度联系,为参数的确定提供更加可靠的依据。     

裂隙岩体渗流–损伤–断裂耦合模型及其应用

 从岩体结构力学和细观损伤力学的角度出发,根据裂隙发育与工程尺度的关系,建立合理且适用的裂隙岩体渗流–损伤–断裂耦合数学模型,该模型能真实反映渗流场与应力场耦合作用下裂隙岩体的损伤演化特性,并能模拟由于渗透压的存在和变化引起的拟连续岩体内翼形裂纹的开裂、扩展和贯通等损伤演化特性和高序次贯通裂隙的张开、闭合。建立考虑渗透压力的三维含水裂隙岩体弹塑性断裂损伤本构方程和损伤应力状态作用下流体渗流方程,给出该数学模型的求解策略与方法,开发裂隙岩体渗流–损伤–断裂耦合分析的的三维有限元计算程序DSDFC.for。该计算程序能模拟岩体分步开挖、应力和渗流边界的动态变化,对裂隙岸坡蓄水加载过程进行渗流–损伤–断裂耦合分析,发现水库蓄水后岸坡山体的竖向抬升,随水位上升岸坡破损区增大,断层塑性区向岸坡深部扩展,与裂隙渗流比较,拟连续岩体渗流滞后。