共查询到20条相似文献，搜索用时 15 毫秒
1.
A. H. Ghazvinian M. J. Azinfar R. Geranmayeh Vaneghi 《Rock Mechanics and Rock Engineering》2012,45(3):349-359
In this study, the shear behavior of discontinuities possessing two different rock wall types with distinct separate compressive
strengths was investigated. The designed profiles consisted of regular artificial joints molded by five types of plaster mortars,
each representing a distinct uniaxial compressive strength. The compressive strengths of plaster specimens ranged from 5.9
to 19.5 MPa. These specimens were molded considering a regular triangular asperity profile and were designed so as to achieve
joint walls with different strength material combinations. The results showed that the shear behavior of discontinuities possessing
different joint wall compressive strengths (DDJCS) tested under constant normal load (CNL) conditions is the same as those
possessing identical joint wall strengths, but the shear strength of DDJCS is governed by minor joint wall compressive strength.
In addition, it was measured that the predicted values obtained by Barton’s empirical criterion are greater than the experimental
results. The finding indicates that there is a correlation between the joint roughness coefficient (JRC), normal stress, and
mechanical strength. It was observed that the mode of failure of asperities is either pure tensile, pure shear, or a combination
of both. Therefore, Barton’s strength criterion, which considers the compressive strength of joint walls, was modified by
substituting the compressive strength with the tensile strength. The validity of the modified criterion was examined by the
comparison of the predicted shear values with the laboratory shear test results reported by Grasselli (Ph.D. thesis n.2404,
Civil Engineering Department, EPFL, Lausanne, Switzerland, 2001). These comparisons infer that the modified criterion can predict the shear strength of joints more precisely. 相似文献
2.
长江三峡库区广泛发育着两侧岩性不同的不连续面（称为异性不连续面）,研究其峰值剪切强度可为相关岩体的稳定性分析和评价提供理论依据。采用高强石膏浇注3组不同形貌且上、下壁面强度不同的不连续面试件,并在不同常法向应力下进行剪切试验。引入不连续面壁组合系数λ来综合量化不连续面壁的抗压强度和基本摩擦角对异性不连续面峰值剪切强度的影响,λ越小,上、下不连续面壁强度差异越大。异性不连续面的峰值剪切强度随λ的增加呈非线性增加,且在高法向应力下更为显著。在Barton公式的基础上,通过多元回归分析建立了估算异性不连续面峰值剪切强度的经验公式。采用天然和人工锯齿形异性不连续面的直剪试验结果对新公式做了进一步验证,试验剪切强度与新公式预测值吻合较好。简要分析了新公式在软硬互层岩质边坡稳定性评价中的应用。最后,讨论了Wu公式的适用性以及新公式的优点和不足。 相似文献
3.
The Shear Behavior of Bedding Planes of Weakness Between Two Different Rock Types with High Strength Difference 总被引：4，自引：2，他引：2
A. H. Ghazvinian A. Taghichian Mahmoud Hashemi S. A. Mar’ashi 《Rock Mechanics and Rock Engineering》2010,43(1):69-87
In this article, the shear behavior of discontinuities caused by bedding planes of weakness between two different rock types
with high strength difference is investigated. The effect of roughness and compressive strength of joint wall in such discontinuities
are studied. The designed profiles consist of two regular and three irregular artificial joints molded by three types of plaster
mortars with different uniaxial compressive strengths. Firstly, it is demonstrated that the shear behavior of discontinuities
with different joint wall compressive strengths (JCS) is different from rock joints with identical wall compressive strengths
by showing that Barton’s empirical criterion is not appropriate for the former discontinuities. After that, some correlation
equations are proposed between the joint roughness coefficient (JRC) parameter and some surface statistical/fractal parameters,
and the normal stress range of Barton’s strength criterion is also modified to be used for such discontinuities. Then, a new
empirical criterion is proposed for these discontinuities in such a way that a rational function is used instead of JRC log10(JCS/σ
n) as i
0(σ
c/σ
n)a/[b + (σ
c/σ
n)
a
] by satisfying the peak dilation angle boundary conditions under zero and very high normal stress (physical infinite normal
stress causing zero peak dilation angle). The proposed criterion has three surface parameters: i
0, a, and b. The reason for separation of i
0 from JRC is indicated and the method of its calculation is mentioned based on the literature. The two remaining coefficients
(a and b) are discussed in detail and it is shown that a shows a power-law relationship with b, introducing the coefficient c through b = c
a
. Then, it is expressed that a is directly related to discontinuity surface topography. Finally, it is shown that the coefficient c has higher values in irregular profiles in comparison with regular profiles and is dominated by intensity of peak dilation
angle reduction (majorly related to the surface irregularity and minorly related to roughness). The coefficient c is to be determined by performing regression analysis on experimental data. 相似文献
4.
In this paper, the effects of shear velocity on the shearing behavior of artificial joints have been studied at different normal stress levels. Here, artificial joints with planar and rough surfaces were prepared with the plaster (simulating soft rock joints) and concrete (medium-hard rock joints) materials. The rough joints had triangular shaped asperities with 10° and 20° inclination angles. Direct shear tests were performed on these joints under various shear velocities in the range of 0.3–30 mm/min. The planar plaster–plaster and planer concrete–concrete joints were sheared at three levels of normal stress under constant normal load boundary condition. Also, the rough plaster–plaster and concrete–concrete joints were sheared at one level of normal stress under constant normal stiffness boundary condition. The results of the shear tests show that the shearing parameters of joints, such as shear strength, shear stiffness and friction angle, are related to the shear velocity. Shear strength of planar and rough plaster–plaster joints were decreased when the shear velocity was increased. Shear strength of concrete joints, except for rough joints with 10° inclination, increased with increasing shear velocity. Regardless of the normal stress level, shear stiffness of both planar plaster–plaster and concrete–concrete joints were decreased when the shear velocity was increased. 相似文献
5.
循环剪切荷载作用下岩石节理变形特性试验研究 总被引：1，自引：0，他引：1
以水泥砂浆为相似材料,制备3种岩壁强度、5种起伏角度的锯齿型节理试样;利用试验设备,进行了在4种法向应力下的循环剪切试验。根据试验结果,结合循环剪切试验特点,定义剪胀角来表征节理循环剪切的法向变形特性,以及剪切刚度来表征节理循环剪切的切向变形特性。基于不同起伏角、不同强度等级和不同法向应力下的节理试样循环剪切试验结果,分析了循环剪切过程中剪胀角和剪切刚度的变化规律;并利用不同条件下的试验结果,对比分析初始起伏角度、法向应力、岩壁强度对节理循环剪切变形特性的影响规律。研究发现：剪胀角、剪切刚度均随着剪切循环次数的增加而呈现先快、后慢的降低趋势,并且中低起伏角度节理的剪胀角、剪切刚度的降低趋势随着初始起伏角度、法向应力的增加而加快,随着岩壁强度增加而变慢,高起伏角度节理的剪胀角、剪切刚度的降低趋势基本保持不变。 相似文献
6.
The variation of the shear strength of infilled rock joints under cyclic loading and constant normal stiffness conditions is studied. To simulate the joints, triangular asperities inclined at angles of 9.5° and 18.5° to the shear movement were cast using high-strength gypsum plaster and infilled with clayey sand. These joints were sheared cyclically under constant normal stiffness conditions. It was found that, for a particular normal stiffness, the shear strength is a function of the initial normal stress, initial asperity angle, joint surface friction angle, infill thickness, infill friction angle, loading direction and number of loading cycles. Based on the experimental results, a mathematical model is proposed to evaluate the shear strength of infilled rock joints in cyclic loading conditions. The proposed model takes into consideration different initial asperity angles, initial normal stresses and ratios of infill thickness to asperity height. 相似文献
7.
In order to study the reliability of the empirical estimation of joint shear strength by the JRC(joint roughness coefficient)-JCS(joint compressive strength) model,natural rock joints of dif-ferent lithologic characteristics and different sizes were selected as samples,and their shear strengths under dry and saturated conditions were measured by direct shear test and compared to those esti-mated by the JRC-JCS model.Comparison results show that for natural rock joints with joint surfaces closely matched,the... 相似文献
8.
Shear behaviour of the joints formed by the interface of two different material types, such as rock and cemented paste backfill, rock and concrete or two different rock types, have practical importance in many rock engineering activities. This paper presents the results of an experimental investigation into the shear behaviour of these special joints under pseudo-static shear velocity. Direct shear tests on concrete–plaster interfaces were carried out under boundary conditions of constant normal load and constant normal stiffness. Shearing velocities of the performed tests were in the range of 0.3–30 mm/min. The results of the shear tests conducted on the planar and rough artificial prepared joints showed that the shearing velocity has a significant influence on the shear strength, friction angle and shear stiffness of the hard–soft material interface. So that, these parameters were decreased when shear velocity was increased. Also, comparison of the tests results that performed on the concrete–plaster joints with those from tests on the plaster–plaster and concrete–concrete interfaces showed that the shear behaviour of concrete–plaster interface is governed mainly by the shear parameters of the plaster block (namely softer material). 相似文献
9.
Debanjan Guha Roy Ashutosh Tripathy T. N. Singh 《Journal of the Geological Society of India》2017,89(3):303-306
Rock discontinuities play a crucial and critical role on the deformational and failure behavior of the rock mass. In most investigations, both the surfaces of the rock joints are considered to have same roughness. But, in nature, the walls of a fresh joint is only expected to be complimentary and to have same roughness. Weathered and water percolating rock joint is most likely to develop different surface roughness on the two opposite walls. So, the shear strength and frictional response behavior derived from the single joint roughness coefficient (JRC) assumption cannot be used in such a condition. To address this shortcoming, we have prepared sandstone blocks with different surface roughness and conducted experiments in a tribometer. The static friction, shear stiffness and coefficient-of-friction of the joint surfaces were calculated and their changes with increasing normal load were noted. One of the major findings of this paper is that, shear strength of the joints may not have a direct correlation with the increasing JRC value of the individual joint walls. Hence, some of the joint walls having higher cumulative JRCs were found to show lower shear strength than those with lowers roughness. This is because, the opposing walls of such joints are not anymore complementary and the frictional resistance is completely controlled by the height and contact area of the asperites. 相似文献
11.
文章通过规则齿形结构面在不同法向应力下的剪切试验,对其力学特性进行了基础性研究,阐述了规则齿形结构面在剪切条件下力学特性的主要特征及其力学特性的主要规律。通过对试验数据的分析,对结构面在剪切力作用下的强度特性以及结构面在剪切条件下的粗糙度特性进行了研究,在此基础上提出了结构面剪切刚度计算模型以及结构面爬坡角与粗糙度系数之间的经验关系,同时对结构面的剪切位移曲线特征进行了描述,并对现象做出了解释。 相似文献
12.
黄土节理种类多样、角度多变,是影响黄土力学性质的重要因素。为研究节理对黄土力学性质影响,开展含预制节理黄土试样单轴与三轴压缩强度试验,分析了非贯通节理对试样剪切破坏模式影响,探讨了节理倾角对黄土强度与变形特性影响规律。结果表明:节理试样剪切破坏均为压剪破坏,破坏模式可分为节理面与破裂面贯通型和节理面与破裂面斜交型,压力作用下非贯通节理尖端翼裂纹和次生裂纹不断萌生,易劣化扩展形成剪切破裂面;节理存在弱化了试样抗变形能力,单轴压缩条件下试样应力-应变曲线均呈应变软化型,预制节理降低屈服阶段变形模量,减小试样剪切破坏位移,加速试样剪切破坏;节理存在显著降低黄土强度,峰值强度与残余强度均随节理倾角呈现先减小后增大变化趋势,但变化幅度随围压增大而降低,黏聚力随节理倾角变化最为敏感,节理倾角60°时试样强度指标最低;预制节理倾角与黄土试样剪切破裂角越接近,节理面越易劣化贯通为剪切破裂面,试样抗变形能力越差,强度性质劣化越显著,试样越容易剪切破坏。研究成果为揭示黄土节理界面劣化对黄土边坡促滑机制提供参考。 相似文献
13.
为研究不同边界条件下剪切速率对岩石节理剪切力学特性的影响,采用RDS-200型岩石节理剪切试验系统对人工浇筑的具有相同节理形貌的不规则水泥节理试样进行了常法向应力和常法向刚度2种边界条件下5种剪切速率的直剪试验。结果表明：（1）常法向应力边界条件下,随剪切速率增大,相同法向应力下的类岩石节理峰前剪切刚度减速增大,峰值剪切强度和残余剪切强度呈对数降低;随剪切速率增大,类岩石节理黏聚力减速增大,内摩擦角呈对数降低。（2）常法向刚度边界条件下,随剪切速率增大,相同法向应力的类岩石节理峰前剪切刚度减速增大,峰值剪切强度呈对数降低,较高法向应力下的残余剪切强度先增大后减小;随剪切速率增大,类岩石节理黏聚力呈对数降低,内摩擦角减速增大。（3）与常法向应力边界条件相比,常法向刚度条件下,节理黏聚力平均增加了115.85%,内摩擦角平均降低了8.44%;相同初始法向应力和剪切速率下,峰前剪切刚度、峰值剪切强度和残余剪切强度分别平均增加了11.96%、19.47%和32.32%,峰值法向位移平均降低了40.12%。该研究结论可为不同剪切速率下地表和地下工程岩体节理的剪切失稳评价提供一定参考。 相似文献
14.
结合Voronoi图随机模拟和3D打印技术制备不规则柱状节理网络模型,采用白水泥浆类岩石相似模型材料浇筑模型并拆模,然后分别采用白乳胶和502胶水作为黏结剂黏结柱体得到两组不规则柱状节理岩体试件,通过对其进行室内单轴压缩试验研究不规则柱状节理岩体强度特性和破坏模式。试验结果表明：不规则柱状节理岩体试件单轴抗压强度随柱体倾角的变化曲线呈现近似“J”型,表现出显著各向异性特征;不规则柱状节理岩体试件典型破坏模式包括沿柱状节理面的劈裂破坏、沿柱状节理面的剪切破坏和沿柱体的压裂破坏等3种,其部分破坏形态有异于规则柱状节理岩体试件。同时,通过与采用净水泥浆作为黏结剂的柱状节理岩体试验结果进行比较,结果表明：采用白乳胶和502胶水作为黏结剂时柱体间黏结强度更低,能够较好反映柱状节理面的弱化效应,试件力学响应与真实柱状节理岩体更为一致。 相似文献
15.
在黏结颗粒模型中引入强度弱化因子生成弱化介质材料,进行弱化模型试件的单轴抗压强度试验。结果表明,弱化作用在降低试件单轴抗压强度的同时,还将导致试件弹性模量逐步下降。这一结果符合相关室内试验的研究成果。为进一步对岩石强度弱化模拟方法进行效果检验,利用颗粒流程序内置的FISH语言建立弱化岩石节理直剪试验模型,进行不同法向应力条件下弱化岩石节理的直剪试验。结果表明：弱化节理模型试件表现出类似于真实节理的一系列宏观剪切力学特征;不同壁面弱化程度条件下,节理模型试件的抗剪强度及剪切峰值膨胀角的试验结果与法向应力的依存关系均符合经典的JRC-JCS模型。由此表明,所采用的岩石强度弱化模拟方法可以较好地再现岩石介质的强度弱化效应。通过模型试件内微裂纹发展演化特征的研究表明,壁面弱化作用可导致试件内裂纹发育数目的快速增长、微裂纹分布范围的迅速扩大,以及剪切裂纹发育比例的迅速提高,由此从细观角度揭示了弱化节理面更易于产生宏观剪切破坏的原因。研究成果可以为弱化岩石节理的抗剪强度及大型岩质边坡的稳定性研究提供参考。 相似文献
16.
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
17.
The strength and deformability of rock mass primarily depend on the condition of joints and their spacing and partially on
the engineering properties of rock matrix. Till today, numerical analysis of discontinuities e.g. joint, fault, shear plane
and others is conducted placing an interface element in between two adjacent rock matrix elements. However, the applicability
of interface elements is limited in rock mechanics problems having multiple discontinuities due to its inherent numerical
difficulties often leading to non-convergent solution. Recent developments in extended finite element method (XFEM) having
strong discontinuity imbedded within a regular element provide an opportunity to analyze discrete discontinuities in rock
masses without any numerical difficulties. This concept is based on partition of unity principle and can be used for cohesive
rock joints. This paper summarizes the mathematical frameworks for the implementation of strong discontinuities in 3 and 6
nodded triangular elements and also provides numerical examples of the application of XFEM in one and two dimensional problems
with single and multiple discontinuities. 相似文献
18.
Laboratory modelling of shear behaviour of soft joints under constant normal stiffness conditions 总被引：1，自引：0，他引：1
Shear behaviour of regular sawtooth rock joints produced from casting plaster are investigated under constant normal stiffness (CNS) conditions. Test results obtained in this investigation are also compared with the constant normal load (CNL) tests. It is observed that the peak shear stress obtained under CNL conditions always underestimates the peak shear stress corresponding to the CNS condition. Plots of shear stress against normal stress show that a nonlinear (curved) strength envelope is acceptable for soft rock joints subjected to a CNS condition, in comparison with the linear or bilinear envelopes often proposed for a CNL condition. Models proposed by Patton (1966) and Barton (1973) have also been considered for the predictions of peak shear stress of soft joints under CNS conditions. Although Patton's model is appropriate for low asperity angles, it overestimates the shear strength in the low to medium normal stress range at higher asperity angles. In contrast, while Barton's model is realistic for the CNL condition, it seems to be inappropriate for modelling the shear behaviour of soft joints under CNS conditions. The effect of infill material on the shear behaviour of the model joints is also investigated, and it is found that a small thickness of bentonite infill reduces the peak stress significantly. The peak shear stress almost approached that of the shear strength of infill when the infill thickness to asperity height ratio (t/a) reached 1.40. This paper also introduces an original, empirical shear strength envelope to account for the change in normal stress and surface degradation during CNS shearing. © Rapid Science Ltd. 1998 相似文献
19.
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
20.
Review of a new shear-strength criterion for rock joints 总被引：44，自引：0，他引：44
Nicholas Barton 《Engineering Geology》1973,7(4):287-332
Barton, N., 1973. Review of a new shear-strength criterion for rock joints. Eng. Geol., 7: 287–332.
The surface roughness of rock joints depends on their mode of origin, and on the mineralogy of the rock. Amongst the roughest joints will be those that formed in intrusive rocks in a tensile brittle manner, and amongst the smoothest the planar cleavage surface in slates. The range of friction angles exhibited by this spectrum will vary from about 75° or 80° down to 20° or 25°, the maximum values being very dependent on the normal stress, due to the strongly curved nature of the peak strength envelopes for rough unfilled joints.
Direct shear tests performed on model tension fractures have provided a very realistic picture of the behaviour of unfilled joints at the roughest end of the joint spectrum. The peak shear strength of rough—undulating joints such as tension surfaces can now be predicted with acceptable accuracy from a knowledge of only one parameter, namely the effective joint wall compressive strength or JCS value. For an unweathered joint this will be simply the unconfined compression strength of the unweathered rock. However in most cases joint walls will be weathered to some degree. Methods of estimating the strength of the weathered rock are discussed. The predicted values of shear strength compare favourably with experimental results reported in the literature, both for weathered and unweathered rough joints.
The shear strength of unfilled joints of intermediate roughness presents a problem since at present there is insufficient detailed reporting of test results. In an effort to remedy this situation, a simple roughness classification method has been devised which has a sliding scale of roughness. The curvature of the proposed strength envelopes reduces as the roughness coefficient reduces, and also varies with the strength of the weathered joint wall or unweathered rock, whichever is relevant. Values of the Coulomb parameters c and Φ fitted to the curves between the commonly used normal stress range of 5–20 kg/cm2 appear to agree quite closely with experimental results.
The presence of water is found in practice to reduce the shear strength of rough unfilled joints but hardly to affect the strength of planar surfaces. This surprising experimental result is also predicted by the proposed criterion for peak strength. The shear strength depends on the compressive strength which is itself reduced by the presence of water. The sliding scale of roughness incorporates a reduced contribution from the compressive strength as the joint roughness reduces. Based on the same model, it is possible to draw an interesting analogy between the effects of weathering, saturation, time to failure, and scale, on the shear strength of non-planar joints. Increasing these parameters causes a reduction in the compressive strength of the rock, and hence a reduction in the peak shear strength. Rough—undulating joints are most affected and smooth—nearly planar joints least of all. 相似文献