共查询到20条相似文献，搜索用时 484 毫秒
1.
预制节理岩体试件强度及破坏模式的试验研究 总被引：2，自引：0，他引：2
采用相似材料模型试验对不同节理倾角、节理贯通度、节理组数、载荷应变率、试件长径比、节理充填物厚度及类型等7种工况下的预制节理岩体在单轴压缩下的峰值强度及破坏模式进行了研究。结果表明：节理岩体的破坏模式及峰值强度与节理构造形态密切相关。贯通节理岩体将产生沿节理面的剪切破坏或穿切节理面破坏,且与第1种破坏模式对应的岩体峰值强度更低。非贯通节理岩体的强度介于完整岩体和贯通节理岩体之间。随着平行节理组数的增加,岩体峰值强度逐渐下降。随着载荷应变率的增加,岩体峰值强度逐渐增大,相应地试件的破坏模式也变得更加复杂。试件长径比基本没有改变其破坏模式,完整试件仍主要是以张拉破坏为主,而节理试件仍以剪切破坏为主。随着长径比增加,试件峰值强度逐渐增大。随着节理充填物厚度增加,试件峰值强度降低。不同节理填充物对试件峰值强度也有一定影响。 相似文献
2.
不同倾角节理组和锚固效应对岩体特性的影响 总被引：1，自引：0，他引：1
首先采用DDARF(discontinuous deformation analysis for rock failure)分析方法对双裂隙岩块进行单轴和双轴压缩模拟试验,研究了裂隙角度和侧向应力大小对岩块特性的影响,得到了裂隙岩块在这两种加载试验中的破坏过程、应力-应变曲线以及岩块中裂隙的起裂应力和岩块的峰值强度。在双轴压缩模拟试验中绘制了裂隙角度为45°的岩块在不同侧向压力下的强度包络线。其次,采用DDARF分析方法模拟劈裂试验中含裂隙试块的锚固效果,得到了4种不同锚固角度试块的轴向荷载–位移变化曲线和裂隙扩展规律。模拟结果与前人的类似条件下的试验结果相符良好。随后又将双裂隙试块双轴压缩模拟试验中得到的参数运用到一个地下洞室的工程实例中,用等效力学特性的方法分析对比了完整岩体和节理岩体洞室开挖完成后的破损状态的差异。最后运用DDARF分析方法研究了随机生成4组节理岩体的地下洞室的稳定性,得到了洞室节理围岩的裂隙扩展过程。同时通过对关键点位移的监测分析了锚杆的锚固效应。 相似文献
3.
This paper presents the results of a series of numerical experiments using the synthetic rock mass (SRM) approach to quantify the behaviour of jointed rock masses. Field data from a massive sulphide rock mass, at the Brunswick mine, were used to develop a discrete fracture network (DFN). The constructed DFN model was subsequently subjected to random sampling whereby 40 cubic samples, of height to width ratio of two, and of varying widths (0.05 to 10 m) were isolated. The discrete fracture samples were linked to 3D bonded particle models to generate representative SRM models for each sample size. This approach simulated the jointed rock mass as an assembly of fractures embedded into the rock matrix. The SRM samples were submitted to uniaxial loading, and the complete stress–strain behaviour of each specimen was recorded. This approach provided a way to determine the complex constitutive behaviour of large‐scale rock mass samples. This is often difficult or not possible to achieve in the laboratory. The numerical experiments suggested that higher post‐peak modulus values were obtained for smaller samples and lower values for larger sample sizes. Furthermore, the observed deviation of the recorded post‐peak modulus values decreased with sample size. The ratio of residual strength of rock mass samples per uniaxial compressive strength intact increases moderately with sample size. Consequently, for the investigated massive sulphide rock mass, the pre‐peak and post‐peak representative elemental volume size was found to be the same (7 × 7 × 14 m). Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
4.
In this paper, an anisotropic strength criterion is established for jointed rock masses. An orientation distribution function (ODF) of joint connectivity, is introduced to characterize the anisotropic strength of jointed rock masses related to directional distributed joint sets. Coulomb failure condition is formulated for each plane of jointed rock masses by joint connectivity, where the friction coefficient and cohesion of the jointed rock mass are related to those of the intact rock and joint and become orientation dependent. When approximating joint connectivity by its second‐order fabric tensor, an anisotropic strength criterion is derived through an approximate analytical solution to the critical plane problem. To demonstrate the effects of joint distribution on the anisotropic strength of jointed rock masses, the failure envelopes are worked out for different relative orientations of material anisotropy and principal stress axes. The anisotropic strength criterion is also applied to wellbore stability analyses. It is shown that a borehole drilled in the direction of the maximum principal in situ stress is not always the safest due to the anisotropic strength of the jointed rock mass. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
5.
工程开挖面附近卸荷扰动区的岩体,受结构面和拉应力共同影响作用,其变形和破坏具有拉剪复合特征。为研究节理岩体的拉剪力学特性,基于颗粒离散元法针对共面断续节理岩体开展了系列数值模拟研究。通过假设粒间接触的力学参数服从Weibull分布表征岩体的非均质性,探讨了非均质性、均质度、法向拉应力和节理连通率对节理岩体拉剪强度和破坏模式的影响。研究表明:拉剪应力条件下非均质性节理岩体主要沿阶梯型破裂面破坏,剪应力-水平位移曲线可以分为线性变形阶段、非线性变形阶段、峰值及峰后阶段;随均质度提高,节理岩体的剪切强度逐渐增加且提升幅度逐渐减弱,趋于均质岩体,岩体中微裂纹由弥散型分布向破裂面集中;节理岩体峰值剪切强度和法向拉应力的大小呈非线性负相关关系;岩体剪切强度随节理连通率增加而显著降低。 相似文献
6.
Strength and Deformational Behaviour of a Jointed Rock Mass 总被引：1，自引：0，他引：1
Summary
An assessment of the strength and deformational response of jointed rock masses is an essential requirement in the site selection,
design and successful execution of Civil and Mining Engineering projects. A quick estimate of these properties for preliminary
evaluation of alternate sites, will reduce considerable expenditures for field tests. An attempt has been made in the present
study to develop a link between strength and deformability of jointed block masses with the properties of intact specimens,
obtained from simple laboratory tests, taking into account the influence of the properties of the joints. Extensive experimentation
has been carried out on large specimens of jointed block masses under uniaxial compression. The model material represents
a low strength rock. Various joint configurations were introduced to achieve the most common modes of failure occurring in
nature. A coefficient called Joint Factor has been used to account for the weakness brought into the intact rock by jointing.
Methods of computing the Joint Factor for various modes of failure of a jointed mass in an unconfined state have been established.
The effect of Joint Factor on strength and tangent modulus of the mass has been studied and the values have been correlated
with those of intact rock. Guidelines for assessing probable modes of failure of a jointed mass will enable one to estimate
the relevant strength and tangent modulus of the mass. 相似文献
7.
拉剪应力状态极易导致岩体破坏乃至失稳,为研究节理岩体拉剪破坏规律,开展了拉剪荷载下共面非贯通节理岩体变形破坏的理论与数值计算研究。通过自定义考虑岩石统计损伤演化的Mohr-Coulomb和最大拉应力准则模型,编写力学参数服从Weibull分布的fish函数,研究了拉剪条件下非均质节理岩体的破坏模式及破坏规律,讨论了岩石均质度、法向拉应力及剪切速率对岩体破坏模式及其力学性质的影响。结果表明,(1) 拉剪应力状态下节理岩体的破坏模式以张拉破坏为主,加载初期破坏位置分布散乱,随着加载和损伤演化逐渐形成带状破裂面,岩体宏观力学性质明显降低;(2) 非均质性对岩体破坏影响显著,主要表现为均质度的增加,岩体由弥散型破坏向集中型破坏转变,破裂面起伏度增大,同时岩体的宏观力学性质增强并最终趋向于均质岩体;(3) 低应力水平下拉应力增大不改变节理岩体以拉张破坏为主的破裂模式,但剪切破坏比例明显减少,同时岩体抗剪强度降低,破裂面的粗糙度增大;(4) 剪切速率对岩体力学性质的影响显著,静态加载范围内岩体抗剪强度随剪切速率的增大而增大,且增幅越来越小。 相似文献
8.
含交叉裂隙岩体相似材料试件力学性能单轴压缩试验 总被引：3，自引：0，他引：3
以相似材料制作含交叉裂隙岩体试件,考虑主裂隙与加载方向之间角度变化及主、次裂隙之间角度变化制作20组试件,对试件进行单轴压缩试验,研究交叉裂隙对岩体破坏模式及力学特性的影响。研究表明,主裂隙与加载方向呈0°及90°时,试件破坏主要为沿次裂隙扩展的剪切型破坏;当主裂隙与加载方向呈30°及45°时,试件破坏主要是沿主裂隙扩展所致的剪切型破坏;主裂隙角度一致情况下,大部分含交叉裂隙岩体破坏强度高于含单向裂隙岩体,含交叉裂隙岩体试件应力-应变曲线峰后下降斜率比含单向裂隙岩体大;主裂隙角度一致情况下,当次裂隙与主裂隙呈45°夹角左右时,岩体试件强度较低,当次裂隙与主裂隙呈30°及90°夹角左右时,岩体试件强度较高。 相似文献
9.
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
10.
Distinct element simulation of ultimate bearing capacity in jointed rock foundations 总被引：1，自引：1，他引：0
Hossein Salari-Rad Mohammad Mohitazar Morteza Rahimi Dizadji 《Arabian Journal of Geosciences》2013,6(11):4427-4434
In this paper, distinct element method numerical modeling is applied to evaluate bearing capacity of strip footing rested on anisotropic discontinuous rock mass. As yet, a little work has been carried out to investigate the effect of joint set orientation on the bearing capacity of rock mass. Generally, the overall behavior of rock mass under loading is very complicated and such analysis should include deformation determination, sliding along discontinuities and failure of rock material. Failure mechanism of rock mass depended on both geometrical parameters of joint sets and strength parameters of rock mass. In this research, it is assumed that rock mass contains one joint set, and therefore the anisotropy in bearing capacity and rock behavior is only due to the existence and orientation of the joint set. In this study, by assuming constant strength parameters and using Mohr–Coulomb failure criterion for the single joint set and nonlinear Hoek–Brown failure criterion for rock material, variation of the bearing capacity values and the type of failure mechanism of rock mass with different joint set dips is investigated. The obtained results indicate that the ultimate bearing capacity of rock mass containing one joint set varies between 27 and 86 % of intact rock. 相似文献
11.
工程岩体强度的估算方法 总被引：1，自引：0，他引：1
岩体是由地质过程中形成的岩块和结构面网络组成。由于试件制备、加荷等均极困难,且昂贵而费时,难于像岩块那样进行大量试验来确定岩体之强度。所以,如何通过室内小试件试验来估算大岩体的强度成为工程地质工作者所关注的问题。本文介绍了两种用小试件资料估算大岩体强度的方法及计算实例。 相似文献
12.
Strength and dilatancy of jointed rocks with granular fill 总被引：1，自引：1，他引：0
Ashutosh Trivedi 《Acta Geotechnica》2010,5(1):15-31
It is well recognised that the strength of rock masses depends upon the strain history, extent of discontinuities, orientation
of plane of weakness, condition of joints, fill material in closely packed joints and extent of confinement. Several solutions
are available for strength of jointed rock mass with a set of discontinuities. There is a great multiplicity in the proposed
relationships for the strength of jointed rocks. In the present study, the author conceives the effect of increasing stresses
to induce permanent strains. This permanent strain appears as micro crack, macro crack and fracture. A fully developed network
of permanent deformations forms joint. The joint may contain deposits of hydraulic and hydrothermal origin commonly known
as gouge. The joint factor numerically captures varied engineering possibilities of joints in a rock mass. The joints grow
as an effect of loading. The growth of the joints is progressive in nature. It increases the joint factor, which modifies
the failure stresses. The dilatancy explains the progressive failure of granular media. Hence, a mutual relationship conjoins
effectively the strength of jointed rock and a dilatancy-dependent parameter known as relative dilatancy. This study provides
a simple and integral solution for strength of jointed rocks, interpreted in relation to the commonly used soil, and rock
parameters, used for a realistic design of structure on rock masses. It has scope for prediction of an equivalent strength
for tri-axial and plane strain conditions for unconfined and confined rock masses using a simple technique. 相似文献
13.
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 总被引：2，自引：0，他引：2
P. H. S. W. Kulatilake Jinyong Park Jeong-gi Um 《Geotechnical and Geological Engineering》2004,22(3):313-330
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. 相似文献
14.
针对工程实际中断续节理裂隙岩体的损伤本构模型,假设岩石微元强度服从Weibull随机分布,以摩尔-库仑破坏准则作为描述微元强度的表示方法,推导出细观损伤变量。利用能量和断裂力学理论,综合考虑节理几何特征及力学特性,推导宏观损伤变量计算公式。基于Lemaitre应变等效假设,考虑宏细观缺陷耦合作用,推导出复合损伤变量,建立了基于摩尔-库仑准则的宏细观缺陷耦合作用的断续裂隙岩体损伤本构模型。研究结果表明：（1）采用摩尔-库仑准则作为描述微元强度的统计分布变量建立的损伤模型能够较好地反映岩石内部缺陷分布和变形特征,该模型真实地反映岩石微元强度受应力状态的影响。（2）该模型建立的理论曲线与断续节理岩体的试验曲线吻合较好。（3）节理裂隙岩体宏观损伤变量及峰值强度随节理倾角的变化规律与综合考虑宏细观耦合作用下的损伤变量及裂隙岩体峰值强度随节理倾角的变化规律基本一致。（4）宏细观耦合作用下的等效弹性模量与节理贯通率呈非线性负相关;在节理倾角一定的情况下,损伤变量与节理长度呈非线性正相关;在贯通率较小时,岩体的宏观损伤变量与内摩擦角的关系呈线性负相关变化,贯通率达到一定程度,线性关系变成非线性关系。 相似文献
15.
《Geomechanics and Geoengineering》2013,8(4):227-238
A three dimensional constitutive model is formulated for deformation analysis of jointed rock masses containing up to three joint sets with arbitrary spatial configurations. A representative elementary volume (REV) that represents the deformational response of the rock mass is defined and the constitutive relationships are developed based on superposition of deformations of the REV components. By representing the constitutive relationships in a tensorial form, the model is able to implement deformation anisotropy of jointed rock masses. The Mohr-Coulomb failure criterion with tension cut-off is used for the intact rock and the joint sets. The model is implemented in FLAC3D and the deformations and strength values calculated by the model are compared with the results from a 3DEC model and analytical solutions. The model results are in good agreement with those obtained from 3DEC. 相似文献
16.
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
17.
Conceived as a potential alternative to the classical design methods employed for analyzing the stability of underground structures driven in jointed rocks, the homogenization approach stems from the heuristic idea that, from a macroscopic point of view, a rock mass cut by a network of joints may be perceived as a homogenized continuum. The strength properties of the latter can be theoretically obtained from the failure conditions of its individual constituents: rock matrix and joint interfaces. At the material level, the limit analysis reasoning is used in the context of homogenization to formulate the homogenized strength criterion of a jointed rock mass in the particular situation of a single set of parallel joints. As it could be expected, the obtained closed‐form expressions show the strength anisotropy induced by joint preferential orientation. The support functions (π functions) associated with the homogenized strength criterion are also determined in both plane strain and three‐dimensional cases. This criterion is then applied to the investigation of stability analysis of a tunnel excavated in a jointed rock mass. Upper bounds estimated of the stability factor are derived from the implementation of the kinematic approach directly on the homogenized underground structure. Finally, the approach is applied to analyze and discuss the collapse of the Pinheiros subway station (São Paulo, Brazil). Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
18.
Characterisation of confinement effect on jointed rock pillars using a Synthetic Rock Mass approach 
下载免费PDF全文
下载免费PDF全文 Confinement effect on jointed rock pillars is numerically characterised in this research using a Synthetic Rock Mass (SRM) approach. The SRM is an integrated model incorporating a discrete fracture network within a Particle Flow Code 3D particle assembly. In this paper, the confinement effect on a 3D jointed pillar SRM model is investigated in a series of simulations, including biaxial compression tests and true and conventional triaxial compression tests. The numerical results suggest that the applied confining stresses generally result in higher pillar strengths and ductile post‐peak responses. More brittle post‐peak behaviour is simulated in the biaxial and true triaxial tests when the pillar is confined by a high stress in one lateral direction and by a zero/low stress in the other lateral direction. This phenomenon is attributed to significant lateral pillar dilation in the less confined direction. Detailed pillar failure modes are monitored in the uniaxial and triaxial tests. Axial splitting fractures and long shear zones cutting through the pillar are simulated when the pillar is able to dilate in the direction of least confinement. Localised shearing along joints and failed rock blocks is the dominant failure mode when the pillar dilation is resisted by the applied confining stresses. The pillar remains relatively intact with limited cracking in the pillar core in the highly confined triaxial tests. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
19.
In nature, there exist several forms of anisotropy in rock masses due to the presence of bedding planes, joints, and weak layers. It is well understood that the anisotropic properties of jointed rock masses significantly affect the stability of surface and underground excavations. However, these critical anisotropic characteristics are often ignored in existing uniaxial dynamic failure criteria. This study investigates the effect of a pre-existing persistent joint on the rate-dependent mechanical behaviours of a rock mass using a particle mechanics approach, namely, bonded particle model (BPM), to realistically replicate the mechanical response of the rock mass. Firstly, in order to capture the rate-dependent response of the jointed rock mass, the BPM model is validated using published experimental data. Then, a dynamic strength model is proposed based on the Jaeger criterion and simulation results. To further investigate the dynamic behaviours, the dynamic uniaxial compressive strength (UCS) for anisotropic rock masses with various joint orientations is investigated by subjecting the BPM models to uniaxial compression numerical tests with various strain rate. The proposed dynamic strength model is validated based on numerical simulation results. Finally, the fragmentation characteristics of the jointed rock masses are analysed, which demonstrate that the failure mode affects the dynamic UCS. This is further confirmed by the analysis of the orientations of microscopic cracks generated by the compression loading. 相似文献
20.
基于Drucker-Prager（下简称D-P）准则,建立压缩载荷作用下的非贯通节理岩石的弹塑性断裂模型。针对节理岩石小范围屈服翼裂纹尖端塑性区,推导了D-P屈服准则的纯I、纯II及I、II复合型3种翼裂纹无量纲塑性区径长函数,并与Mises准则的塑性区进行对比;结果表明,D-P准则的I型和复合型塑性区较Mises屈服准则的塑性区大,且其II型及I、II复合型塑性区在翼裂纹上下表面不连续。进一步,引入断裂软化因子以表征节理岩石裂隙断裂扩展后的断裂软化规律,考虑非贯通节理岩石复合型断裂软化,是由于节理尖端翼裂纹应变能密度超过最小应变能密度导致其成核扩展引起的,提出用应变能密度的指数函数形式表征断裂软化变量的演化;塑性屈服函数采用Borja等的应力张量3个不变量的硬化/软化函数,反映塑性内变量及应力状态对硬化函数的影响;建立节理岩石的弹塑性断裂本构关系及其数值算法,并用回映隐式积分算法编制了弹塑性断裂模型的程序。以单轴压缩下非贯通节理岩石为例,分析岩石断裂韧度、节理摩擦系数和节理倾角等参数的影响,结果表明,所提出的弹塑性断裂模型与数值和试验结果比较吻合。 相似文献