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1.
针对目前节理岩体损伤本构模型中仅考虑节理等宏观缺陷造成的损伤,而没有考虑岩块中微裂纹等微观损伤的不足,提出了综合考虑宏微观损伤的节理岩体本构模型。其中微观损伤模型采用基于应变强度理论和岩石微元强度服从Weibull分布假定的统计损伤模型,把其应用于被节理切割而成的岩块。而宏观损伤模型主要基于连续介质力学原理,把节理对岩体性质的劣化作为损伤来考虑。在考虑节理传压及传剪系数的基础上,提出了综合考虑宏微观复合损伤的节理岩体本构模型。算例表明宏观节理的存在大大削弱了岩体的强度,降低了其刚度,增大了其柔性。所提出的模型能够较好地反映宏微观两类损伤对岩体应力-应变关系及强度的影响,较为合理。 相似文献
2.
岩石节理剪切变形对岩体工程的安全性和稳定性具有重要影响。为研究常法向应力下岩石节理剪切变形本构关系,采用RDS-200型岩石直剪仪对非规则砂岩节理进行了不同法向应力下的直剪试验。根据岩石节理剪切应力?位移全程曲线形状特征,将其依次划分为峰前压密阶段、线性阶段、屈服阶段和峰后软化阶段;根据剪切应力在峰后软化阶段降低幅度和速率大小,将岩石节理剪切应力?位移曲线划分为3种类型：峰后平台型、峰后缓降型和峰后跌落型。基于岩石节理剪切应力?位移曲线各阶段剪切变形特征,采用分段函数建立了岩石节理剪切变形本构模型。与其他模型相比,新提出的岩石节理剪切变形本构模型对试验数据拟合精度更高,更好地描述了岩石节理剪切应力?位移全程曲线。另外,在通过岩石节理直剪试验由经验公式确定模型参数之后,所提出本构模型可在不同法向应力下实现对不同粗糙度岩石节理剪切应力?位移曲线的预测。研究结果对岩石节理剪切变形的数值模拟和工程估计具有一定的实用价值。 相似文献
3.
Prof. M. Oda T. Yamabe Y. Ishizuka H. Kumasaka H. Tada K. Kimura 《Rock Mechanics and Rock Engineering》1993,26(2):89-112
Summary An elastic stress-strain relation is formulated in terms of crack tensors which makes it possible to take into account explicitly the effect of joints on elastic behavior of rock masses. The present study is to discuss some related topics which may be encountered in its practical application. Two problems are solved by incorporating the elastic stress-strain relation into a program for three-dimensional finite element analyses; i. e., stress concentration by surface loading and displacement by excavation of an intersecting tunnel. Validity of the results is checked by comparing them with a laboratory model test and a field test, with the following conclusions: The overall distribution of stress definitely depends on a joint stiffness ratio (i. e., normal stiffness to shear stiffness). If the ratio is chosen as unity, the stress concentration occurs mainly in the direction parallel to major joints. If the ratio is high, say 10, then the stress concentrates along the perpendicular as well as the parallel directions to major joints. It can be said, on the basis of the fairly good agreement of the calculations using the high stiffness ratio with the field and laboratory measurements, that the elastic solution by crack tensors provides a practical tool for estimating the stress and strain in strongly jointed rock masses. 相似文献
4.
柱状节理岩体原位变形试验力学浅析与模拟 总被引：1，自引：0，他引：1
在白鹤滩坝址区柱状节理岩体原位变形试验成果的基础上,针对节理刚度的取值进行讨论,利用柔性中心孔试验值反算得到柱状节理岩体节理面刚度值。岩体变形是由岩块和节理两部分组成,分析含单节理岩体概念模型的单轴加、卸载规律性和其变形特性,发现其滞回特性是节理力学行为造成的;推导得到了岩体变形计算公式,可用于多组相交节理岩体等效弹性模量的计算,能够反映出节理岩体的各向异性特征;建立了柱状节理随机模型,采用离散元方法和反算的刚度值进行了仿真分析,得到等效变形参数在试验结果范围内。 相似文献
5.
节理岩体蠕变特性研究 总被引：13，自引：3，他引：10
在已知岩石和节理蠕变规律的前提下,推导了节理岩体蠕变模型的一般表达式。假定岩石体积变形和节理法向压缩变形为弹性变形,忽略节理的剪胀现象,认为只有岩石畸变和节理剪切滑移与时间有关,从而推导了含三组相交节理的岩体蠕变模型及其参数。根据反演出的岩石和节理蠕变模型,计算了含三组相交节理的岩体在单轴应力作用下一些节理参数对岩体单轴蠕变的影响。分析表明,节理间距、剪胀系数以及节理夹角都对岩体的单轴蠕变变形有明显影响。节理间距越大,剪胀系数越大,节理夹角越小,节理岩体的单轴蠕变柔量也就越小,岩体的蠕变变形也越小。 相似文献
6.
城市地下管线采用承插式接口连接,管线结构的连续性与否取决于接口刚度。然而,现有研究大都假定地下管线为连续结构,忽略了接口转角对管线变形的影响。开展土工离心模型试验和两阶段有限元参数分析,系统研究了盾构下穿不同接口刚度管线的变形特性。发现非连续管线的薄弱接口导致其整体抗弯刚度明显小于连续管线,且接口转动导致非连续管线具有更好的与土体协调变形能力。因此,盾构下穿施工引起的非连续管线沉降明显大于连续管线。非连续管的结构连续性假定将大大低估管线沉降。盾构下穿引起的接口转角与地层损失呈线性关系。基于系统的有限元参数分析,建立了区分相对刚性、柔性管线的无量纲组。针对相对刚性、柔性的非连续管线,分别建立了管节相对长度、管-土相对刚度与接口转角的预测方法,利用离心模型试验结果验证了预测方法的合理性。新方法能有效地预测盾构穿越地下管线的接口转角,研究成果可应用于城市地下管网改造工程。 相似文献
7.
针对柱状节理岩体的构造特性,采用水泥砂浆等材料制作出具有不同柱体倾角且含有横向节理分布的柱状节理岩体模型,并通过单轴压缩试验,研究柱体倾角和横向节理对岩体各向异性力学特性及破坏机制的影响。结果表明：试样峰值强度和变形模量随柱体倾角变化曲线均近似为U形,并体现出典型的各向异性特征;随着柱体倾角的变化,试样单轴压缩破坏模式可分为垂直于柱体轴向的劈裂破坏、沿纵向节理面的剪切滑移破坏、滑移破坏与劈裂破坏同时发生的复合破坏和平行于柱体轴向的劈裂破坏4类;横向节理的存在降低了柱状节理岩体沿柱轴方向的完整性,并影响了劈裂破坏裂纹的分布与扩展,因此,横向节理切割柱体是影响柱状节理岩体承载能力的重要因素。 相似文献
8.
粗糙度是影响节理岩体强度与变形特性的重要因素之一。首先使用3D 打印机制作模具,并浇筑形成不同粗糙度（节理粗糙度系数JRC=2、7、12、17、22）的节理岩石试样。采用GCTS高温高压动静岩石三轴试验系统,对含有不同粗糙度节理岩石试样进行了三轴压缩试验,获得了不同粗糙度节理岩石试样的三轴应力–应变曲线,分析了JRC对岩石三轴强度和变形特性的影响规律,在三轴加载过程中采用声发射测试系统,分析了不同粗糙度节理岩石试样的声发射特性。运用数字三维视频显微系统观察节理面形态,讨论了不同围压下节理岩石试样峰值强度与JRC之间的关系。研究结果表明,节理面的存在直接导致节理岩石试样强度的大幅度降低,JRC对岩石破坏裂纹的形态、数量和空间分布特征亦有很大的影响,随着JRC值的增大,岩石节理面的抗剪强度增大,岩石试样的三轴抗压强度也会增大,岩石试样由脆性破坏转变为延性破坏。 相似文献
9.
Summary The jointed roof in laminated rock mass may be capable of self-support and sustaining transverse load and can be analysed by the voussoir beam notation. There are three main failure modes of a voussoir beam structure: crushing in the high stress areas, buckling without localised material failure and shear sliding along the joints. Previous studies on the voussoir beam have concentrated on the crushing failure mode, assuming that the voussoir beam would not fail by shear sliding prior to reaching its crushing strength. However, the possibility exists that the voussoir beam may collapse by shear sliding along the joints with a strength much lower than that predicted by the estimation method for crushing failure, depending upon the joint properties. Hence the stability analysis of a jointed roof without considering the shear sliding failure may lead to disastrous consequences. In this paper a numerical and experimental study has been carried out to analyse the shear sliding failure of voussoir beams containing vertical and inclined joints with one or more mid joints. Equations for verification of shear sliding are proposed and effects of the voussoir beam geometry and material properties on the shear sliding failure are also discussed. 相似文献
10.
Microplane damage model for jointed rock masses 总被引：1，自引：0，他引：1
The paper presents a new microplane constitutive model for the inelastic behavior of jointed rock masses that takes into account the mechanical behavior and geometric characteristics of cracks and joints. The basic idea is that the microplane modeling of rock masses under general triaxial loading, including compression, requires the isotropic rock matrix and the joints to be considered as two distinct phases coupled in parallel. A joint continuity factor is defined as a microplane damage variable to represent the stress‐carrying area fraction of the joint phase. Based on the assumption of parallel coupling between the rock joint and the rock matrix, the overall mechanical behavior of the rock is characterized by microplane constitutive laws for the rock matrix and for the rock joints, along with an evolution law for the microplane joint continuity factor. The inelastic response of the rock matrix and the rock joints is controlled on the microplane level by the stress–strain boundaries. Based on the arguments enunciated in developing the new microplane model M7 for concrete, the previously used volumetric–deviatoric splits of the elastic strains and of the tensile boundary are avoided. The boundaries are tensile normal, compressive normal, and shear. The numerical simulations demonstrate satisfactory fits of published triaxial test data on sandstone and on jointed plaster mortar, including quintessential features such as the strain softening and dilatancy under low confining pressure, as well as the brittle–ductile transition under higher confining pressure, and the decrease of jointed rock strength and Young's modulus with an increasing dip angle of the joint. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
11.
To obtain the compression–shear infiltration characteristics of joint rock, the coupled compression–shear infiltration tests of samples were carried out under different loading and boundary conditions. The shear dilatation, permeability and the change laws of hydraulic opening of jointed rockmass were obtained under different normal stiffness and loading conditions. It is shown that the contact area gradually becomes smaller and smaller with the relative sliding of two jointed surfaces. And the contact ratio is down to a minimum value when the main processes of the jointed surface reach the peak shear strength. The remaining main processes is gradually destroyed, the contact ratio of joint surface becomes larger after the main processes reaches the peak strength. The contact ratio tends to be stable until all processes were all destroyed. Due to the influence of the joint surface protrusion, the normal displacement is smaller and then increases with the increase of shear displacement. The less the stiffness of jointed rock mass is, the greater the over water area of the joint surface is, the greater the permeability is, the greater the final stability value of the hydraulic opening degree is. The theoretical basis is provided for the fractured rock mass formed of permeable channels, initiation and outbreak of permeability disaster evolution process. 相似文献
12.
节理对卸荷条件下岩体的力学性质有重要影响。通过含2条不同间距预制断续节理岩体的三轴卸荷破坏试验,研究了节理岩体在卸荷应力条件下的应力-应变特征、强度、变形特征、破坏规律及节理间距对岩体力学性质的影响。研究表明：相比于完整岩体,节理岩体卸荷破坏时从峰值强度跌落至残余强度过程中轴向应变较大,为完整岩体的3～4倍,岩体破坏时极限强度明显低于完整岩体,脆性特征不如完整岩体明显;节理岩体卸荷破坏时,变形模量有较大幅度的降低,其降低程度是同条件下完整岩体的6～7倍,节理间距越大,变形模量降低程度越大;与含预制节理岩样三轴加载试验结果相比,节理岩体卸荷条件下破坏程度更为强烈,除剪切破裂面外,沿最大主应力方向分布的不同级别的张性裂隙非常发育,预制节理的间距对岩体破坏形态影响不大。 相似文献
13.
在岩土工程中,裂隙岩体经常处于峰后变形状态,研究裂隙岩体的峰后应力-应变关系对预测结构的稳定性有重要意义。基于峰后软化阶段强度参数的逐渐演化行为,首先提出一个求岩石峰后应力-应变关系和裂隙峰后应力-切向位移关系的一般方法。然后采用摩尔-库仑强度准则,以岩石的最大主应变和裂隙的切向位移作为软化参数,假设强度参数为软化参数的分段线性函数,分岩体沿裂隙滑移破坏和沿岩石剪切破坏两种情况,提出多组贯穿裂隙岩体峰后应力-应变关系式的求法。最后,在算例中,分岩体沿裂隙滑移破坏和沿岩石剪切破坏两种情况给出了裂隙岩体的峰后应力-应变曲线,讨论了裂隙的平均间距、法向刚度和剪切刚度对峰后应变的影响。结果表明,裂隙的平均间距、法向刚度和剪切刚度越小,裂隙岩体的轴向应变越大。 相似文献
14.
Constitutive laws for rock joints should be able to reproduce the fundamental mechanical behaviour of real joints, such as dilation under shear and strain softening due to surface asperity degradation. In this work, we extend the model of Plesha to include hydraulic behaviour. During shearing, the joint can experience dilation, leading to an initial increase in its permeability. Experiments have shown that the rate of increase of the permeability slows down as shearing proceeds, and, at later stages, the permeability could decrease again. The above behaviour is attributed to gouge production. The stress–strain relationship of the joint is formulated by appeal to classical theories of interface plasticity. It is shown that the parameters of the model can be estimated from the Barton–Bandis empirical coefficients; the Joint Roughness Coefficient (JRC) and the Joint Compresive strength (JSC). We further assume that gouge production is also related to the plastic work of the shear stresses, which enables the derivation of a relationship between the permeability of the joint and its mechanical aperture. The model is implemented in a finite element code (FRACON) developed by the authors for the simulation of the coupled thermal–hydraulic–mechanical behaviour of jointed rock masses. Typical laboratory experiments are simulated with the FRACON code in order to illustrate the trends predicted in the proposed model. © 1998 by John Wiley & Sons. Ltd. 相似文献
15.
针对目前节理岩体损伤变量定义中大多仅考虑节理长度、倾角等几何性质,而未考虑节理抗剪强度等力学性质的不足,基于断裂力学中的由于单个节理存在引起的附加应变能增量与损伤力学中的损伤应变能释放量相关联的观点,推导出了在双轴应力下含单条非贯通闭合节理岩体的损伤变量计算公式,并根据断裂力学理论对双轴压缩荷载下的单个节理尖端应力强度因子计算方法进行了研究,得出了应力强度因子KⅠ、KⅡ的计算公式;同时考虑多节理间的相互作用,给出了单组单排及单组多排非贯通节理尖端应力强度因子计算公式,由此建立了相应的节理岩体双轴压缩损伤本构模型,并利用该模型进行了相应的算例分析。结果表明：对含单条非贯通闭合节理的岩体而言,当节理倾角小于其内摩擦角时,岩体强度与完整岩石相同,岩体损伤为0,而后随着节理倾角增加,岩体强度、损伤随节理倾角的变化分别呈开口向上及向下的抛物线,当节理倾角约为60°时,岩体损伤最大,强度最低。随着节理长度增加,岩体损伤增加,而随着节理内摩擦角的增加,岩体损伤则减小;对含单组单排非贯通闭合节理的岩体而言,当节理总长度一定时,随着单条节理长度的减小及节理条数的增加,岩体损伤则逐渐减小,但其减小幅度与节理条数并不呈线性关系。 相似文献
17.
微震、工程爆破等低应力循环剪切荷载作用对节理岩体工程失稳破坏具有重要影响。为研究峰前循环剪切加卸载作用下岩石节理剪切力学特性,采用RDS-200型岩石节理剪切试验系统对人工劈裂黄砂岩节理进行了峰前循环剪切下的直剪试验。通过与未进行峰前循环剪切加卸载时岩石节理力学参数预测值对比,得到峰前循环剪切加卸载作用对峰前剪切刚度、峰值剪切强度、峰值剪切位移与残余剪切强度的影响。结果表明：（1）峰前循环剪切加卸载后,当法向应力为2 MPa时,岩石节理峰前剪切刚度增大,当法向应力为4～10 MPa时,岩石节理峰前剪切刚度在循环剪切应力幅值范围内增大,在超出循环剪切应力幅值时减小;（2）峰前循环剪切加卸载后,峰值剪切强度降低了10%～20%,降低百分比随法向应力增大整体呈对数函数增大;峰值剪切位移增加了2%～40%,增加百分比随法向应力增大整体呈对数函数减小;（3）峰前循环剪切加卸载后,岩石节理残余剪切强度无明显变化,峰值剪切强度与残余剪切强度差值减小,峰后剪切应力做功损失百分比降低。 相似文献
18.
从宏观分析与微观机制方面探讨了围压、孔隙水压力对岩体应力应变曲线峰后特性即脆－延性转变的影响。定义了一个峰后破坏割线模量 来表征孔隙水压力对岩体应力应变曲线转型的影响,并结合斜坡失稳的刚度判据,进一步分析了孔隙水压力对应力应变曲线峰后斜率的影响,随孔隙水压力的增加,峰后曲线斜率变陡,峰后刚度增大,即材料的均匀性、脆性增大与刚度比k减小。因此在围压等外界环境因素及系统内部条件不变时,刚度比 时就存在一个临界孔隙水压力 ,也就是说降雨等涨落因素引起滑面介质中的孔隙水压力大于这个临界值时斜坡就易于发生突变失稳。从而进一步加深认识了降雨等外部涨落因素对斜坡系统失稳的重要触发作用。 相似文献
19.
Study of rock joints under cyclic loading conditions 总被引：11，自引：3，他引：11
Summary A conceptual model for the behaviour of rock joints during cyclic shear and under constant normal stresses was proposed according to results from shear tests with 50 concrete replicas of rock joints. The shear strength and deformability of joint samples were found to be both anisotropic and stress dependent. Based on these experimental results, a two-dimensional constitutive model was developed for rock joints undergoing monotonic or cyclic loading sequences. The joint model was formulated in the framework of non-associated plasticity, coupled with empirical relations representing the surface roughness degradation, appearance of peak and residual shear stresses, different rates of dilatancy and contraction, variable normal stiffness with normal deformation, and dependence of shear strength and deformability on the normal stress. The second law of thermodynamics was represented by an inequality and used to restrict the values of some of the material parameters in the joint model. The new joint model was implemented into a two-dimensional Distinct Element Method Code, UDEC, and its predictions agreed well with some well-known test results. 相似文献
20.
为研究砂土充填对节理抗剪强度的影响,利用GCTS（RDS?200型）岩石剪切测试系统对4种不同摩擦系数砂土充填的粉晶大理岩节理进行了直剪试验。结果表明：相同法向应力下,未充填节理的峰值剪切应力大于充填节理的峰值剪切应力,说明砂土的存在降低了节理的剪切强度;由节理面三维形貌参数最大谷深 表征节理面粗糙程度,得到了未充填节理的峰值剪切强度公式,公式预测值与试验值基本吻合;得到了用充填砂土摩擦系数表达的充填节理峰值剪切强度公式,公式预测值与试验值较为吻合。研究结论对充填节理岩体稳定性评价具有一定指导意义。 相似文献