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岩体结构面的抗剪强度是表征岩体强度的一项重要参数,但由于原位试验受场地等诸多因素影响,难以大规模的开展,本文提出在室内用结构面大型剪切试验开展结构面的剪切特性研究,以某水电站坝基砂岩岩体中的硬性结构面为研究对象,取得了较好的成果。试验表明:结构面的多组剪切变形曲线具有一定的应变硬化的特征;达到峰值剪切强度时的剪切位移普遍较大,在8.9mm~44.5mm之间;砂岩中硬性结构面光滑面的“基本摩擦角”为31.4°,结构面“平均起伏角”为6.3°。 相似文献
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本文采用剪切试验装置,探讨了复剪、反复加卸剪应力、含水率、正应力和岩性对光滑结构面力学特性的影响,得出了初剪与复剪时、水饱合状态下与干燥状态下的光滑结构面抗剪强度都具有峰值转换性,复杂加载比简单加载的抗剪强度大。所得结论对于进一步认识岩体结构面的基本力学特性有重要作用. 相似文献
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一种基于复变量求导法的岩土体抗剪强度参数反演新方法 总被引:2,自引:1,他引:1
边坡稳定性分析中,岩土体(含结构面)抗剪强度参数的确定至为重要.工程实践中利用边坡上实测的位移数据反演岩土参数是一种理想的参数确定方法.当前采用的位移反分析方法在反演弹性模量、泊松比及地应力等参数时已经取得了较好的成果,但在反演抗剪强度参数时仍未获得理想的结果.本文针对岩土体抗剪强度参数反演中所存在的困难,将复变量求导法、优化方法以及岩土弹塑性有限元法结合起来,提出一种适用于岩土体抗剪强度参数的反演分析新方法,通过测点实测位移反演计算出岩土体的抗剪强度参数.算例结果表明,该方法具有较高的计算精度和搜索效率,是一种值得推广的位移反分析方法. 相似文献
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岩质边坡结构面抗剪强度是分析边坡稳定性的重要参数。反分析法是视滑坡将要滑动而尚未滑动的瞬间为极限平衡状态,求解滑动面抗剪强度的一种方法,相对于室内实验和原位测试具有成本低的特点,但其普适性较差,对反分析法的应用条件进行研究对该方法在边坡工程中的准确应用具有重要意义。本文用反分析和室内试验两种方法确定西柏坡纪念馆不稳定斜坡结构面抗剪强度,发现对于单滑动面岩质顺层滑坡,直接采用滑坡断面进行反分析获得的结构面抗剪强度与室内试验结果相近,可用于评价同一结构面边坡的稳定性。 相似文献
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危岩稳定性分析方法 总被引:10,自引:0,他引:10
通过试验建立了同时考虑危岩主控结构面贯通率和防治工程安全等级的危岩主控结构面抗剪强度参数贯通率法;按照出现频率,将作用在危岩体上的荷载拟定为三种荷载组合(工况).认为处于特大型水利工程区或高频率强烈地震区的一级防治工程,应将设计荷载组合调整为"自重+裂隙水压力(暴雨状态)+地震力";基于极限平衡理论详细推导了滑塌式危岩、倾倒式危岩和坠落式危岩在不同荷载组合下的稳定系数计算方法,结合稳定性评价标准,系统建立了危岩稳定性分析方法.应用这种危岩主控结构面抗剪强度参数贯通率法确定的c、ψ值比规范推荐的长度加权方法随机性要小,经2001~2007年现场观测验证计算结果是比较符合实际情况的. 相似文献
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岩体强度很大程度上取决于结构面的强度,板理化岩体尤其如此。通过原位测试直接获得岩体结构面的强度参数对于岩体稳定性分析和工程设计都具有重要意义。为了解板理化岩体板理结构面的强度性质,选择北京房山区晓幼营白云质板理化岩体进行了结构面强度的原位测试研究。鉴于传统岩体原位直剪试验成本高和操作难的情况,在掌握北京地区构造应力资料的基础上,在试验中考虑岩体中板理结构面的产状与构造应力方向的关系,提出了一套利用地应力提供原位试体剪切面法向力的测试分析方法:开挖出不同方向、不同解除状态的3个试体(试坑); 试坑中两个平行的解除面与原岩之间形成一定距离的空间,自然构成了施加水平试验荷载的反力框架,从而免除了传统试验中笨重的试验反力装置。由于解除面组合的变化,试体受到的构造应力状态有相应的变化,与试验荷载叠加后在预定剪切面上形成了不同大小法向力和切向力。上述方法免除了笨重的反力装置,取得了一定的实验效果,确定了被测岩体结构面的强度参数:黏聚力c和摩擦角φ,对原位岩体结构面强度测试方法进行了一次有益的新尝试,得到的岩体结构面的强度参数为类似板岩地区大型输电线路塔杆地基设计及岩体稳定性分析提供了参考。 相似文献
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边坡工程中,结构面抗剪强度是非常重要的力学参数,合理地选择确定抗剪强度的方法,常常要分析c、φ值在边坡稳定中的作用。根据极限平衡原理,对10~30m高的平面滑动型边坡不同抗剪强度的控稳结构面c、φ值在边坡稳定中的作用进行了定量分析。研究表明c值对稳定系数的影响随坡高增大逐渐减弱,φ值对稳定系数的影响随坡高增大逐渐增强。得到了不同坡高下c、φ值边坡稳定作用等值曲线,该曲线很容易确定抗剪强度参数c、φ值在边坡稳定中的作用。 相似文献
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Most problems faced by the practicing rock mass engineering involve the evaluation of rock mass dynamic strength and deformability. As part of a rock mass, the mesoscopic flaws such as the microcracks and the macroscopic ones such as the joints both inherently affect the rock mass dynamic strength and deformational behavior. Nearly none of the existing models can handle the co-effect of these two kinds of flaws on the rock mass dynamic mechanical behavior. This study focusses on the rock mass with multi-sets of non-persistent joints and establishes a mathematical model accounting for the anisotropy in dynamic strength and deformability induced by the joints. Accordingly, an approach incorporating the existing models or methods to enable perfect simulation of the dynamic stress-strain relationship of a rock mass is proposed, in which the joint geometrical parameters such as the joint length and dip angle, the strength ones such as the joint internal friction and the deformational ones such as the joint normal and shear stiffness can all be taken into account. In order to investigate the validity of the proposed model, a series of calculation examples have been made and the results fits very well with the theoretical ones. 相似文献
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《Comptes Rendus Mecanique》2019,347(8):561-575
The scale effect of rock joint shearing is of great significance in rock engineering. Most existing shear constitutive models could describe the pre- and post-peak deformation of rock joints, but only in one particular scale, that is, those existing models will fail to depict the rock joint shearing in different length scales. Therefore, this study aims to establish a constitutive relationship for rock joints with considering the scale effect. Based on the assumption of a random statistical distribution of rock material strength and statistical mesoscopic damage theory, damage variables are defined as the ratio of the number of damaged elements to the total number in the shear process. Together with the nonlinear relationship between the microelement failure and the joint scale, an empirical statistical constitutive relationship for joint is established. And then, the determination method of constitutive relationship parameters and the variation laws with the scale are discussed. Results show that the predicted results of the proposed empirical relationship not only agree well with the experimental results but also fully describe nonlinear deformation, pre-peak softening, post-peak softening, residual stage, and other mechanical properties of the shear deformation of joint with different dimensions, thereby demonstrating the rationality of the constitutive relationship. The physical meaning of the constitutive relationship parameters is clear, and the expressions of the constitutive relationship parameters can be deduced from the experimental results. In addition, the influence of scale effect on the shear deformation of rock joints can be quantified using parameters, which help accurately describe the action form of scale effect. 相似文献
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Ang Liu Guanghui Tian Qingzhao Zhang Wenli Lin Jingcai Jiang 《Comptes Rendus Mecanique》2018,346(12):1179-1191
The stress relaxation characteristic of rock mass is an important aspect of rheology and has important practical significance for rock engineering. In order to investigate the relaxation characteristic of rock joints with different slope ratios and normal stresses, a series of shear stress relaxation tests were conducted on artifical rock joints poured by cement mortar. Test results show that the relaxation curves can be divided into three stages, i.e. instantaneous relaxation stage, attenuation relaxation stage, and stable relaxation stage. Furthermore, the nonlinear Maxwell relaxation equation was obtained by using the relation between the viscosity coefficient and time, and the theoretical curves based on the empirical equation agreed well with the test results. Moreover, the change law of the initial viscosity coefficient was investigated. Accordingly, a stress relaxation method, termed as relaxation stress peak method, was proposed to determine the long-term strength of rock joints. 相似文献
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The particle flow code 2D (PFC2D) is used to establish a coplanar, non-persistent joint model. Three joint distribution types, namely, both-side (type a), scattered (type b), and central (type c), are set according to their position. Numerical simulations of the direct shear test are conducted to investigate the effect of non-persistent joint distribution and connectivity on shear mechanical behavior. Simulation results are in good agreement with the analytical solutions to Jennings' criterion, and show: (1) type-c and type-b joints have high strength, whereas type-a joints have low strength. Shear strength and modulus increase with a decrease in joint persistency, and the shear displacement that correspond to shear strength increases with a decrease in persistency. (2) The brittle failure characteristics of the sample are evident when the intact rock bridge area is large. Reinforcement at both ends of the joint limits shear deformation, and shear strength can be effectively improved when joint persistency is large. The small-area dispersed reinforcement joint method cannot effectively improve shear strength. (3) The comprehensive shear strength parameters and the shear strength of the non-persistent joints can be predicted well using Jennings' criterion. Cohesion is the dominant factor that controls shear strength. 相似文献
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断续节理将对工程岩体的强度及变形等力学特性产生显著影响,损伤力学中视节理为岩体的一种宏观损伤,因而采用损伤张量来刻画其对岩体的影响。目前学术界提出了用节理的几何、强度及变形等3类参数来描述节理的物理力学性质,而目前的岩体损伤张量计算方法都只涉及前2类参数,均没有涉及其变形参数即法向及切向刚度。为此,在前人研究的基础上,基于断裂及损伤理论提出了考虑节理法向及切向刚度的单轴压缩下单条断续节理引起的损伤张量计算公式,进而通过考虑节理间相互作用给出了单组单排或多排节理岩体损伤张量计算公式。其次,以岩石细观动态损伤模型为基础,结合宏细观损伤耦合观点提出了一个能够同时考虑节理几何、强度及变形参数的断续节理岩体动态损伤本构模型。最后,利用该模型讨论了节理参数及载荷应变率等对岩体动态力学特性的影响,认为节理长度减小及摩擦角增大将导致岩体动态峰值强度及弹性模量增大;岩体动态峰值强度及弹性模量则随着节理法向及切向刚度的增大分别减小或增大;而当节理法向及切向刚度按照同一比例增大时,岩体动态峰值强度及弹性模量则是增大的。岩体动态峰值强度与载荷应变率呈正相关。 相似文献
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基于离散元模型的土石混合体直剪试验分析 总被引:6,自引:0,他引:6
土石混合体是由高强度块石和低强度土体组成的一类特殊工程地质材料,其力学性质可通过直剪试验进行确定。本文针对土石混合体的细观材料特性,分别采用球形颗粒单元和非规则组合颗粒单元模拟土体和块石材料,对其在不同含石量和颗粒粘结强度下的直剪试验过程进行离散元分析。计算结果表明,土石混合体的抗剪强度随着含石量和粘结强度的增加而增加;通过不同法向应力下直剪试验的离散元分析,确定了不同含石量下土石混合体材料的内摩擦角和粘聚力。本文研究结果有助于进一步揭示土石混合体的抗剪强度特性。 相似文献
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Stability analysis of jointed rock slope 总被引:2,自引:0,他引:2
The stability analysis of a jointed rock slope with two sets of unfilled joints, under its own weight, is carried out directly by considering failure surfaces along some particular joints and also going through the intact rock. Simple failure mechanisms using uniform rigid rock-block motions are incorporated in the yield design kinematic approach. They yield an improvement of known results as long as the characteristics strength of the joints are weak enough. 相似文献