基于强度参数脆性指数的岩石Ⅰ型断裂韧度评价

在试验数据收集基础上,选取3种典型强度脆性指数作为考察对象,建立Ⅰ型断裂韧度与脆性指数之间的线性关系,得到基于不同脆性指数的岩石Ⅰ型断裂韧度参数化模型。通过引入交叉验证法获得准确的模型参数,并对模拟结果进行检验,评价各模型的适用性和相互之间的差异。结果表明:3种评价模型在评价和预测岩石Ⅰ型断裂韧度上均有很强的可靠性,可以借助脆性指数评价岩石的Ⅰ型断裂韧度;3种模型的评价和预测精度存在一定差异,总体来看,基于莫尔圆脆性指数的评价模型优于压拉强度脆性指数评价模型和抗压强度脆性指数评价模型,从而证明Ⅰ型断裂韧度是岩石综合力学性质的体现,利用多强度指标建立评价模型将会获得更准确、合理的Ⅰ型断裂韧度值;由于抗压强度获取便捷,利用其建立的评价模型也具有较高的评价精度,在要求快速评价时,可优先考虑选择基于抗压强度脆性指数的岩石Ⅰ型断裂韧度评价模型。     

页岩脆性的室内评价方法及改进

 页岩气储层脆性对页岩的脆性进行测试、评价具有重要的意义。鉴于此,通过文献调研和室内测试,总结脆性测试的20种基本方法,包括基于强度、硬度和坚固性的评价方法,并重点讨论基于全应力–应变特征的页岩脆性测试原理和试验方法。针对页岩脆性破裂机制结合断裂特征定义脆性,认为页岩的脆性是材料的综合特性,受自身非均质性和外在测试环境共同影响;峰后与峰前应力–应变特征均是表征脆性的关键,模拟地下环境的全应力–应变测试能够提高脆性评价的准确度;试样破坏前抵抗非弹性变形的能力和破坏后承载力丧失速度的快慢是脆性强弱的主要力学表现。为提高脆性评价的准确性,对已有的力学测试方法提出改进方案。开展室内真三轴岩石力学实验,对我国南方黑色页岩的脆性特征进行评价。     

裂纹线场分析方法在岩石力学中的应用

 将岩体破坏主控结构面上的裂纹视为共线等间距裂纹,利用裂纹线上的合理条件将共线裂纹受压剪应力的问题简化为有限宽岩体内含有一条裂纹受压剪应力的问题;把岩体材料的屈服准则作为求解该问题的基本方程,运用线场分析方法在裂纹线附近区域得到弹塑性解析解。分析裂纹面闭合所产生的裂纹面上的摩擦强度对裂纹线附近应力场的影响,通过在裂纹线上提出的合理条件和弹塑性应力场在其边界上的匹配条件,得出裂纹线上塑性区范围与压剪荷载的关系,并获得岩体沿主控结构面的裂纹贯通破坏的强度准则。通过与试验结果的对比分析后发现所提出理论是合理的,研究结果可为岩体断裂力学的发展提供有力依据。     

基于应力–应变曲线的岩石脆性特征定量评价方法

 脆性是岩石的一种重要性质,岩石的许多力学行为都与其脆性有关。总结现有的基于强度、应力–应变曲线、加卸载试验、硬度、矿物成分等脆性指标,并详细分析这些指标在评价岩石脆性时的局限性。为合理、准确评价岩石的脆性程度,提出一种建立在应力–应变曲线峰后应力降的相对大小和绝对速率基础上、能够考虑岩石塑性屈服特性和应力状态影响的新的脆性指标,并开展单轴和三轴压缩实验对新指标进行检验。试验结果表明：水泥砂浆和大理岩脆性程度均随围压增大而减小,相同应力状态下大理岩脆性程度均大于水泥砂浆,这与二者实际脆性程度相符;单轴试验条件下灰岩、大理岩、花岗岩和红砂岩的脆性程度依次减小,破坏时的轴向应变逐渐增大,这与“应变越低脆性程度越大”吻合。试验结果可很好地验证该脆性指标的可靠性,研究成果对丰富和改进现有的岩石脆性特征评价方法具有重要意义。     

反倾岩质边坡破坏的力学机制研究

以反倾岩质边坡为研究对象,建立了由一组结构面切割时边坡稳定性系数的力学计算方法。根据岩块结构面的受力模式,构建了岩块结构面的断裂力学模型,并基于断裂力学建立了各岩块结构面等效应力强度因子的求解方法和稳定性判据。引入Kelvin蠕变模型,获得了t 时刻岩块结构面等效应力强度因子的求解方法和结构面长度计算方法,为反倾岩质边坡的防治和监测提供了理论依据。以边坡内各岩块的转角为关联变量,量化了岩块转动后岩块间的相互作用力,建立了岩块转角的计算方法。最后,通过实例分析,表明建立的反倾岩质边坡破坏的力学分析方法计算结果与实际情况基本一致。     

Identification of visco-elastic models for rocks using genetic programming coupled with the modified particle swarm optimization algorithm

The response of rocks to stress can be highly non-linear, so sometimes it is difficult to establish a suitable constitutive model using traditional mechanics methods. It is appropriate, therefore, to consider modeling methods developed in other fields in order to provide adequate models for rock behavior, and this particularly applies to the time-dependent behavior of rock. Accordingly, a new system identification method, based on a hybrid genetic programming with the improved particle swarm optimization (PSO) algorithm, for the simultaneous establishment of a visco-elastic rock material model structure and the related parameters is proposed. The method searches for the optimal model, not among several known models as in previous methods proposed in the literatures, but in the whole model space made up of elastic and viscous elementary components. Genetic programming is used for exploring the model's structure and the modified PSO is used to identify parameters (coefficients) in the provisional model. The evolution of the provisional models (individuals) is driven by the fitness based on the residual sum of squares of the behavior predicted by the model and the actual behavior of the rock given by a set of mechanical experiments. Using this proposed algorithm, visco-elastic models for the celadon argillaceous rock and fuchsia argillaceous rock in the Goupitan hydroelectric power station, China, are identified. The results show that the algorithm is feasible for rock mechanics use and has a useful ability in finding potential models. The algorithm enables the identification of models and parameters simultaneously and provides a new method for studying the mechanical characteristics of visco-elastic rocks.     

脆性岩石起裂应力水平与脆性指标关系探讨

 脆性指标与起裂应力作为岩石力学性质的内在体现,均反映岩石的非均质性和结构上的差异,二者存在一种必然的联系,通过理论研究和算例分析来探讨起裂应力水平与基于单轴抗压、抗拉强度比值的脆性指标的关系。首先,归纳总结基于压拉比、全应力–应变特征及硬度或坚固性的28种基本脆性测试方法。然后,研究硬脆性岩石单轴压缩起裂机制,讨论基于裂纹体积应变拐点的起裂应力确定方法,并定义起裂应力水平指标K。最后,结合具体工程算例探讨岩石起裂应力与基于压拉比的脆性指标的函数关系,深入验证起裂应力水平和脆性指标间内在联系的必然性。得出以下结论：(1) 以岩石单轴抗压、抗拉强度为纽带,建立起裂应力水平和脆性指标间的函数关系,根据单轴压缩起裂应力与单轴抗拉强度的关系,进一步验证脆性指标与起裂应力水平存在内在联系的必然性。(2) 岩石起裂应力水平与脆性指标B5和B6存在明显的函数关系,起裂应力水平与B5呈幂函数关系,与B6呈线性函数关系,相关系数均大于85%。(3) 采用起裂应力水平指标重新定义脆性指标,通过岩石的室内单轴压缩试验,由起裂应力水平可以快速得到岩石的脆性指标。通过这一研究,丰富了岩石起裂应力与脆性指标的关系,为脆性指标的计算提供了一条新思路。     

Physical reconstruction and mechanical behavior of fractured rock masses

Physical modeling of rock masses containing complex fracture geometries is an important but very challenging task in rock mechanics and rock engineering. In this work, a novel integration of 3D printing and water-soluble casting is presented for the preparation of rock-model specimens with fracture networks, which is similar to the lost-wax casting process. The fracture network is created with water-soluble polyvinyl alcohol (PVA) material by 3D printing. The intact rock matrix is prepared with cement paste. Uniaxial compressive tests combined with the digital image correlation (DIC) technique are conducted to investigate the mechanical properties and failure process of the prepared rock-model specimens. The differentiation rate of the effective variance is defined to recognize the precursory anomalies during the loading process. The mechanical anisotropy is further investigated by a series of rotated models. The results show that the proposed methodology has distinct advantages for replicating rocks with complex fracture geometries in terms of high accuracy for fabricating fracture networks, high repeatability of mechanical properties, and high strength and brittleness of rock matrices. Due to the presence of complex fracture geometries, the nonlinear mechanical responses of the fractured rock-model specimens, including strain-softening and anisotropy, are observed in our experiments.

     

岩石中断裂力学的研究

在断裂力学的基础上,研究了岩石破坏类型和受压裂缝的扩展,并对微裂缝演化进行了探讨,提出利用断裂力学中的裂纹尖端应力和应变场的分布情况,可以预测和制止岩体的失稳。基于能量平衡建立岩石裂纹的扩展条件,进而导出断裂稳定性准则。指出岩石断裂力学中存在的一些问题,并对研究要点进行了总结,为岩石断裂问题研究提供了理论依据。     

岩石地基上有筋扩展基础的断裂力学模型分析

由于岩石地基刚度比基础刚度大、岩石地基变形量小等特点,岩石地基上扩展基础的基底反力和受力特性与土质地基应有所不同。本文鉴于岩石地基上扩展基础受力特点,建立断裂理论模型,推导了岩石地基上有筋扩展基础Ⅰ-Ⅱ复合型断裂准则,利用断裂准则提出了计算岩石地基上有筋扩展基础抗剪承载力的方法。本文的结论对岩石地基上扩展基础的设计和研究具有参考意义。     

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.     

岩土材料局部化变形分岔分析

分析岩土材料和工程中分岔现象，探讨了这些分岔行为产生的机理。详细介绍数学、力学结构以及岩土材料局部化变形分岔分析理论，指出目前的分析方法无法分析岩土失稳过程中剪切带由韧性逐渐转化为脆性，最后发生破坏的过程。应用塑性可膨胀本构关系，结合对称性群论方法和反对称变形分岔分析的初步模拟结果表明：此方法存在一定的局限性。初步提出基于Desai的扰动态概念模型建立的损伤本构关系，进行峰后分岔分析以及率相关和动态加卸载过程分岔的分析。     

非贯通节理岩体单轴压缩动态损伤本构模型

非贯通节理岩体是同时含有节理、裂隙等宏观缺陷及微裂隙、微孔洞等细观缺陷的复合损伤地质材料,基于此提出了在非贯通节理岩体动态损伤本构模型中应同时考虑宏、细观缺陷的观点。首先对基于细观动态断裂机理的经典动态损伤本构模型——TCK模型进行了阐述,其次针对目前节理岩体损伤变量定义中仅考虑节理几何参数而未考虑其强度参数的不足,基于能量原理和断裂力学理论推导得出了同时考虑节理几何及强度参数的宏观损伤变量(张量)的计算公式;第三,基于Lemaitre等效应变假设推导了综合考虑宏、细观缺陷的复合损伤变量(张量);第四,借鉴前人基于复合材料力学的观点,考虑了节理法向及切向刚度等变形参数对岩体动态力学特性的影响,进而建立了基于TCK模型的非贯通节理岩体单轴压缩动态损伤本构模型。并利用该模型讨论了载荷应变率、节理内摩擦角、节理厚度、节理法向及切向刚度和节理倾角等对岩体动态力学特性的影响规律。计算结果与目前的理论及试验研究结果比较吻合,从而说明了该模型的合理性。     

Application of artificial intelligence to rock mechanics: An overview

Different artificial intelligence(AI)methods have been applied to various aspects of rock mechanics,but the fact that none of these methods have been used as a standard implies that doubt as to their generality and validity still exists.For this,a literature review of application of AI to the field of rock mechanics is presented.Comprehensive studies of the researches published in the top journals relative to the fields of rock mechanics,computer applications in engineering,and the textbooks were conducted.The performances of the AI methods that have been used in rock mechanics applications were evaluated.The literature review shows that AI methods have successfully been used to solve various problems in the rock mechanics field and they performed better than the traditional empirical,mathematical or statistical methods.However,their practical applicability is still an issue of concern as many of the existing AI models require some level of expertise before they can be used,because they are not in the form of tractable mathematical equations.Thus some advanced AI methods are still yet to be explored.The limited availability of dataset for the AI simulations is also identified as a major problem.The solutions to the identified problems and the possible future research focus were proposed in the study subsequently.     

岩体表征单元体与岩体力学参数

在岩体多场耦合分析中,许多采用岩体表征单元体(REV)讨论岩体的渗透特性。事实上,岩体REV是岩石力学的一个基本科学问题,它是选取岩体力学模型以及确定岩体力学参数的基础。从REV的基本概念出发,阐述岩体REV的力学意义;根据岩石及岩体的结构和地质特征,定义了岩石力学中常见的6个尺度,并分析了REV与其它尺度的关系;归纳总结并提出了岩体REV的3种确定方法:能量叠加法,地质统计法,数值模拟法;讨论了岩体REV与岩体力学模型及岩体力学参数取值之间的关系;提出了岩体力学参数的"5S"相关性和岩体力学参数场的概念和分析方法。     

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。     

Assessment of brittleness using rock strength and density with punch penetration test

Brittleness fracturing of rock is one of the most popular research areas in rock engineering, since some rocks show brittle fractures under loads. Direct standard testing method for measuring rock brittleness have not available yet. Therefore, rock brittleness is indirectly obtained as a function of rock strength. The aim of this study is not only to introduce direct method to measure rock brittleness as an index via punch penetration test, but also to investigate the relationship between intact rock properties (uniaxial compressive strength, Brazilian tensile strength, and density of rock) and the brittleness measured from the test. To obtain these objectives, rock cores were gathered from 48 tunnel projects throughout the world. Followings the sampling, the samples were prepared and relevant rock tests were carried out to establishment of dataset at the Earth Mechanics Institute of Colorado School of Mines in the USA. Consequently, using generated dataset, new brittleness index (BI_m) and rock brittleness classification was introduced base on type, strength and density of rock together with result of punch penetration test. Further, the rock brittleness index was predicted as a function of the uniaxial compressive strength, Brazilian tensile strength and density of rock with correlation coefficient of 0.94.     

光测方法在岩石力学实验观测中的应用述评

综述了常用光测方法在岩石力学实验观测中的应用,总结了这些光测方法相对于岩石力学中常用的其他方法的特点。最后在分析岩石力学实验观测新趋势的基础上,指出发展一种以数字散斑相关方法(DSCM)为基础的岩石力学观测系统,将可以满足岩石力学观测中的新的需要。     

中国深层岩石力学研究及在石油工程中的应用

论述了深层岩石力学的研究范围、特点，介绍了深层岩石力学的全尺寸钻井模拟试验，地应力、岩石断裂韧性、动静态岩石力学参数获取方法和技术，以及在钻井过程中的井壁稳定预测检测技术、水力压裂的室内物理模拟技术、数值模拟技术等问题的研究进展，并提出了深层岩石力学面临的挑战和需要解决的技术问题。     

基于岩石破坏全过程能量演化的脆性评价指数

 目前用于评价页岩可压性的脆性指数大都孤立地考虑峰值前后的力学特性,并不能反映岩石整个破坏过程的脆性特征。基于岩石的全应力–应变曲线,分析岩石材料由塑性变形转化为脆性断裂过程中各种应变能的演化规律,认为峰前耗散能和峰后断裂能水平是决定岩石是否发生脆性断裂的本质因素。结合这2种能量建立能反映岩石破坏前后力学特征的脆性评价指数,对不同岩石材料在不同围压下的脆性特征以及页岩脆性的各向异性进行评价。研究结果表明：建立的脆性评价指数能同时反映岩石脆性破坏的难易程度和脆性的强弱,可评价不同力学条件下的脆性变化特征。不同岩石材料峰前耗散能以及峰后断裂能随着围压增大而增大,脆性程度不断降低,但降低趋势有所不同,红砂岩和页岩分别在低围压时和高围压时出现了脆–塑性的转化,而花岗岩在围压不断增大的整个过程中都保持着较强的脆性。另外页岩脆性具有明显的各向异性,不同层理方向的页岩所表现出的脆性程度差异显著,随着层理倾角?的增大,页岩脆性表现出稳–减–增的变化趋势,? = 0°时页岩的脆性程度要强于? = 90°时,? = 60°时页岩脆性最弱且表现出很强的塑性特征。实验结果很好地验证了提出的脆性指数的可靠性,研究成果为岩石脆性的定量评价提供了一条新思路。