岩石直接拉伸与压缩变形的试验研究

采用自行研制的可对同一岩石试样进行单轴压缩和直接拉伸的试验装置,对3种岩石进行了压缩和直接拉伸试验。结果表明,这3种岩石的压缩弹性模量均大于拉伸弹性模量,压缩与拉伸弹性模量之比分别为1.1,1.4,2.5。压缩泊松比也大于拉伸泊松比。研究表明：直接拉伸下切线泊松比随荷载的增加而减小,与压缩下泊松比的变化相反。     

随机分布贯穿裂隙岩体变形特性研究

洞室开挖后,其周边通常会产生许多随机分布的贯穿裂隙,直接影响洞室围岩稳定,研究随机分布贯穿裂隙岩体的变形及变形特性具有重要意义。基于线弹性理论和线性刚度理论计算岩石和裂隙的位移,用概率的方法建立了随机分布贯穿裂隙岩体变形的计算模型,给出了随机分布贯穿裂隙岩体的等效弹性模量和等效泊松比,研究了岩石和裂隙的材料参数和几何参数对岩体等效弹性模量和等效泊松比的影响。可得如下结论：等效弹性模量和等效泊松比随着岩石弹性模量的增大而增大;等效泊松比随着岩石泊松比的增大而增大;等效弹性模量和等效泊松比随着裂隙法向刚度的增大而增大;随着剪切刚度的增大,等效弹性模量逐渐增大,而等效泊松比则逐渐减少;随着裂隙平均间距的增大,等效弹性模量逐渐减小,等效泊松比在平均倾斜角较小时逐渐增大,在平均倾斜角较大时逐渐减小;随着裂隙平均倾斜角的增大,等效弹性模量先减小后增大,而等效泊松比先增大后减小。模型能较全面地考虑构成岩体的岩石和裂隙的材料参数与几何参数对岩体变形的影响,其结果对研究洞室围岩的变形和工程设计有一定的参考价值。     

岩石力学性质的应变率效应试验

以玄武岩为试样,开展了中低应变率下的岩石单轴抗压试验。本次研究分析应变率对岩石抗压强度、弹性模量、泊松比等力学参数的影响,分别提出了岩石抗压强度、弹性模量、泊松比等参数与应变率之间的拟合关系式。以峰值应力对应的应变和峰值后的软化模量为脆性评价指标,分析加载应变率对岩石脆性的影响。研究表明:(1)岩石抗压强度、弹性模量均随应变率的增加而增加。(2)岩石泊松比随应变率增加而减小。(3)随着应变率增加大,峰值应力对应的应变增大,峰值后的应变软化程度减小,岩石脆性减弱。(4)应变率对岩石抗压强度影响较大,对弹性模量和泊松比的影响较小。(5)曲线拟合效果良好,提出的拟合关系式合理。     

岩石力学参数对裂缝发育程度的影响

弹性模量(E)、泊松比(μ)及密度(ρ)是岩石的重要力学参数, 当其他条件一致时, 在一定程度上影响着裂缝的发育。以塔里木盆地某气田为研究区, 在造缝期古应力场分析的基础上, 利用储层裂缝数值模拟技术, 计算得到储层裂缝孔隙度; 再以裂缝孔隙度为指标, 分析岩石力学参数对裂缝发育程度的影响。研究结果表明, 裂缝孔隙度随弹性模量的增加而增大, 同等应力条件下, 弹性模量越大, 裂缝孔隙度越高, 破裂程度越大; 泊松比小于0.2时, 裂缝孔隙度随泊松比增加而逐渐下降; 泊松比超过0.2后, 裂缝孔隙度随泊松比增加而逐渐增大; 岩石密度对裂缝孔隙度的影响不大, 基本上可以忽略。      

深部矿山不同埋藏深度岩石拉压力学特性试验研究

岩石的物理力学特性随埋藏深度增大会发生变化。本文以云南某矿山900～1200 m深度范围内4个不同埋藏深度的矿体上下盘围岩(灰质白云岩)为研究对象,开展了不同含水条件下(自然状态和饱水状态)的单轴压缩和巴西劈裂试验,探明深部岩石力学基本物理力学特性随埋深的变化规律。研究结果表明：在研究的深度范围内,岩石基本物理成分组成及结构相似,随着岩石埋藏深度的增加,岩石试样的密度、纵波波速、单轴抗压强度、抗拉强度和弹性模量等均略微增大,而泊松比呈先增大后减小的趋势。含水条件对岩石的力学特性影响显著,不同埋藏深度的岩石试样进行饱水处理后其抗压强度、抗拉强度和弹性模量均明显减小,泊松比显著增大,其中岩石单轴抗压强度对水的敏感性高于其他参数对水的敏感性,各参数对水的敏感性排序为：抗压强度>弹性模量>泊松比>抗拉强度。本研究很好地揭示了深部矿山不同埋藏深度围岩的拉压力学特性变化规律。     

岩石负泊松比的探讨

基于热力学原理，泊松比允许范围为－１≤σ≤０．５。虽然具有负泊松比的物质在理论上是存在的，但是除低密度泡沫材料，具有负泊松比的物质没有被发现。当岩石的纵速度与横波速度之比＜√２，则泊松比为负值。     

弹性模量和泊松比对边坡稳定安全系数的影响

根据土的弹性模量和泊松比满足双曲线关系，给出了弹性模量和泊松比折减的基本原理。通过算例分析表明，调整泊松比对安全系数的求解是有影响的，而弹性模量的影响一般较小。算例亦表明，位移控制方法具有较高的稳定性和收敛性，在运用有限元强度折减方法求解边坡的安全系数时，建议采用位移控制方法来控制其收敛性。     

丹江口水库区岩石软化性能试验研究

通过采用岩样干燥、自然和饱和状态下的物理力学性能试验,对丹江口水库库区代表性岩样的软化性能进行了研究,以此探讨岩石软化作用,为丹江口水库续建工程诱发地震机理研究提供基础数据。结果表明,随着试件含水率的增加,岩石单轴抗压强度、弹性模量和泊松比均下降,岩石的软化系数与孔隙比有直接关系。     

岩石单轴压缩试验Kaiser效应实质的研究

岩石 Kaiser效应具有记忆先前应力、纵向应变和横向应变的能力 ,记忆的准确程度随加载阶段不同而不同。为了解 Kaiser效应的记忆实质 ,通过岩石单轴压缩试验确定 Kaiser效应对体积应变、弹性模量和泊松比三项物性参数的记忆能力。结果表明 ,岩石 Kaiser效应具有记忆先前物性参数的能力 ,其中尤以对弹性模量的记忆能力表现为最好 ,而且受时间因素影响不大 ,说明岩石 Kaiser效应的实质是对其内部物理特性的记忆     

元坝气田地应力测井计算研究

运用测井资料研究地应力,对元坝气田钻井、储层改造和开发有重要意义。利用测井资料对气田地层的岩石力学参数(抗压强度、抗张强度、泊松比、弹性模量、内聚力、内摩擦角等)进行了计算;用压裂资料反演求取构造应变系数;借鉴前人的研究成果,确定地层孔隙压力和孔弹性系数;应用组合弹簧理论地应力计算模型,建立元坝气田地应力计算方法。通过岩心声发射法地应力实验验证了该方法的准确性,并从地层埋深、岩性变化方面分析了该区地应力剖面特征,指导了后期套管选择、钻井施工方案等设计。     

Coal strength and Young's modulus related to coal rank,compressional velocity and maceral composition

This paper presents an experimental investigation of coal rank and maceral composition influences on the coal mechanical behaviors. The complete stress–strain behavior, uniaxial compressive strength, Young's modulus, and acoustic compressional velocity were measured and correlated to coal ranks and microstructures. The test results show that coal is an elasto-brittle geo-material and its uniaxial compressive strength and Young's modulus increase as coal rank increases. This occurs because as vitrinite reflectance or coal rank increases, coal has less microporous structure and thus higher uniaxial compressive strength. Therefore, using vitrinite reflectance value instead of vitrinite content is advantageous for correlating coal strength. The experimental results also demonstrate that compressive strength and Young's modulus have positive exponential correlation, even for different types of coal. Therefore, the compressive strength of coal is highly related to its Young's modulus. The uniaxial compressive strength and acoustic compressional velocity of coal are also correlated, but a single correlation does not exist for different coal ranks; instead, different relationships occur for different types of coal.     

页岩各向异性力学特性微观测试方法研究

页岩力学各向异性特征是地应力、井壁稳定、水力裂缝扩展相关研究的重要基础参数。针对页岩力学各向异性宏观测试中存在样品制取困难、制样成功率低的特点,采用来源丰富的钻井岩屑或破碎岩块,通过研究纳米压痕实验原理、实验方法和数据解释方法,采用连续刚度测试方法对平行层理和垂直层理的页岩试样进行纳米压痕测试;基于硬度的分类准则将纳米压痕数据分为三类主要矿物基质进行合理解释,采用接触刚度法计算硬度、杨氏模量,采用能量法计算断裂韧性,得出了页岩粘土基质的杨氏模量、硬度和断裂韧性。测试结果表明这种基于硬度的分类准则处理纳米压痕数据是方便合理的。页岩粘土基质力学特性在纳米尺度上具有各向异性,纳米尺度力学参数与层理方向相关。页岩不同力学参数的各向异性表现不同,杨氏模量各向异性较弱,断裂韧性各向异性较强。平行层理方向断裂韧性为垂直层理方向断裂韧性的80%。     

On the linear elastic responses of the 2D bonded discrete element model

The bonded discrete element model (DEM) is a numerical tool that is becoming widely used when studying fracturing, fragmentation, and failure of solids in various disciplines. However, its abilities to solve elastic problems are usually overlooked. In this work, the main features of the 2D bonded DEM which influence Poisson's ratio and Young's modulus, and accuracy when solving elastic boundary value problems, are investigated. Outputs of numerical simulations using the 2D bonded DEM, the finite element method, a hyper elasticity analysis, and the distinct lattice spring model (DLSM) are compared in the investigation. It is shown that a shear interaction (local) factor and a geometric (global) factor are two essential elements for the 2D bonded DEM to reproduce a full range of Poisson's ratios. It is also found that the 2D bonded DEM might be unable to reproduce the correct displacements for elastic boundary value problems when the represented Poisson's ratio is close to 0.5 or the long-range interaction is considered. In addition, an analytical relationship between the shear stiffness ratio and the Poisson's ratio, derived from a hyper elasticity analysis and applicable to discontinuum-based models, provides good agreement with outputs from the 2D bonded DEM and DLSM. Finally, it is shown that the selection of elastic parameters used the 2D bonded DEM has a significant effect on fracturing and fragment patterns of solids.     

岩石多次全过程压入硬度的测试试验

介绍了在ＭＴＳ８１５型岩石力学试验机上配置专用夹具和平底圆柱压模后成功地进行岩石表面多次全过程压入破碎试验的情况,分析了这种试验方法与传统的单次压入硬度测试法相比在反映岩石破碎过程特征、表征岩石压入硬度方面所具有的优点。最后邮进一步研究应解决的几个问题。     

Modelling the elastic behaviour of granular materials

A review of the literature indicates that the elastic behaviour of granular materials is isotropic and that Poissony's ratio is constant, whereas Young's Modulus, the bulk modulus and the shear modulus vary with the mean normal stress and the deviatoric stress. A nonlinear, isotropic model for the elastic behaviour is developed on the basis of theoretical considerations involving the principle of conservation of energy. Energy is therefore neither generated not dissipated in closed-loop stress paths or in closed-loop strain paths. The framework for the model consists of Hooke's law, in which Poission's ratio is constant and Young's modulus is expressed as a power function invlving the first invariat of the stress tensor and the second invariant of the deviatoric stress tensor. The characteristics of the model are described, and the accuracy is evaluated by comparison with experimental results from triaxial tests and three-dimensional cubical triaxial tests with a variety of stress paths. Parameter determination from unloading–reloading cycles in conventional triaxial compression tests is demonstrated, typical parameter values are given for granular materials and extension of the model to soils with effective cohesion is described.     

Thermo‐hydro‐mechanical modeling with Langmuir's adsorption isotherm of the CO2 injection in coal

In this paper, we used a theoretical model for the variation of Eulerian porosity, which takes into account the adsorption process known to be the main mechanism of production or sequestration of gas in many reservoir of coal. This process is classically modeled using Langmuir's isotherm. After implementation in Code_Aster, a fully coupled thermo‐hydro‐mechanical analysis code for structures calculations, we used numerical simulations to investigate the influence of coal's hydro‐mechanical properties (Biot's coefficient, bulk modulus), Langmuir's adsorption parameters, and the initial liquid pressure in rock mass during CO₂ injection in coal. These simulations showed that the increase in the values of Langmuir's parameters and Biot's coefficient promotes a reduction in porosity because of the adsorption process when the gas pressure increases. Low values of bulk modulus increase the positive effect (i.e., increase) of hydro‐mechanical coupling on the porosity evolution. The presence of high initial liquid pressure in the rock mass prevents the progression of injected gas pressure when CO₂ dissolution in water is taken into account. Copyright © 2014 John Wiley & Sons, Ltd.     

A discrete element approach to elastic properties of layered geomaterials

Discrete element methods (DEMs) are used for layered geomaterials to investigate the dependency of traditional engineering constants on material properties and loading conditions. Shear deformations and compression tests parallel and perpendicular to layering are conducted on samples of varying kerogen volume fractions, confining pressures, porosities, and layer geometries. The goal of this article is to develop a method to better characterize oil shale (a transversely isotropic layered geomaterial) while eliminating high experimental costs. The DEM simulations conducted in this study demonstrate strong dependencies of Young's modulus, Poisson's ratio, and shear modulus on kerogen volume fraction and porosity. Furthermore, a rule of thumb for layer thickness and particle resolution is proposed for simulation design. Results agree well with robust effective medium theories, solidify the ability of DEM to model the mechanical properties of layered heterogenous materials, and encourage the use of DEM to study more complicated layered media and material failure. Copyright © 2011 John Wiley & Sons, Ltd.     

Estimation of rock mass strength and deformability in 3-D for a 30 m cube at a depth of 485 m at Äspö Hard Rock Laboratory

The rock fracture data provided by Swedish Nuclear Fuel and Waste Management Company were used to develop a 3-D stochastic fracture network model for a 30 m cube of Äspö diorite located at a depth of 485 m at Äspö Hard Rock Laboratory, Sweden. This fracture network model was validated. A new procedure is developed to estimate rock block strength and deformability in three-dimensions allowing for the anisotropy and incorporating the inherently statistical fracture geometry for the selected cube. The mean rock mass strength was found to be 47% of the mean intact rock strength of 297 MPa at 485 m depth. The mean rock mass modulus was found to be 51% of the intact rock Young's modulus of 73 GPa. The rock mass Poisson's ratio was found to be 21% higher than the intact rock Poisson's ratio of 0.28. These percentages indicate the level of weakening of the rock mass due to the presence of fractures. The ratio of mean major principal rock mass strength/mean minor principal rock mass strength turned out to be 1.28. The ratio of mean major principal rock mass modulus/mean minor principal rock mass modulus turned out to be 1.21.     

全国地质资料馆数字地质资料馆主站日志数据集

为更加准确的摸清地质资料用户的需求,消除资料使用者与资料管理者之间的信息鸿沟,全国地质资料馆开展了数字地质资料馆主站访问日志的数据收集工作。数据集采用计算机自动记录的方法,将访问者的所在地、关键词、IP地址等信息进行完整记录。为了更好的利用这些数据,采用了规范的数据处理方法和质量控制体系。数据集提供了2014—2017年数字地质资料馆主站的访问记录,有效地反映了访问者在进行地质资料获取过程中的行为习惯,可为日后地质资料网站建设、地质资料开发利用、地质资料的管理与服务提供依据。