Test Study on Dynamic Mechanical Property of Jointed Rock Mass

2013 ◽  
Vol 868 ◽  
pp. 282-286 ◽  
Author(s):  
Li Min Zhang ◽  
Shu Ran Lv ◽  
Hong Yan Liu
Keyword(s):  
Rock Mass ◽  
Failure Mode ◽  
Failure Modes ◽  
Dynamic Strength ◽  
Strain Ratio ◽  
Jointed Rock ◽  
Jointed Rock Mass ◽  
Tensile Failure ◽  
Dip Angle ◽  
Joint Center

Failure modes of jointed rock mass with different joint dip angle, joint center continuity degree, joint sets, load strain ratio and joint filling width under SHPB test are studied with model tests. The results show that failure modes and dynamic strength of jointed rock mass are much related to joint geometry. To rock mass with a single joint, its strength and failure mode are greatly controlled by the joint dip angle. The dynamic strength of the samples with joint dip angle 0° and 90°, whose failure modes are both tensile failure, is 90% and 71% of that of intact one, respectively. The dynamic strength of the samples with joint dip angle 60° is nearly zero. The dynamic strength of the samples with joint dip angle 30° and 45°, whose failure modes are mainly shear failure with partly tensile failure, is 50% and 18% of that of intact ones, respectively. The dynamic strength of the samples with 1/4, 1/2 and 4/5 joint center continuity degree is 95%, 74% and 28% of that of intact one, respectively. The dynamic strength of the samples with 1, 2 and 3 sets of joints is 54%, 23% and 10% of that of intact one, respectively. The dynamic strength of the intact and jointed samples both increases with load strain ratio, and the sensitivity to load strain ratio of the former is much higher than that of the latter, whose failure mode becomes more complicated accordingly. With increase of joint fillings width, the samples dynamic strength decreases gradually, but its failure mode does not change.

Analysis of TBM Tunnel Behavior in Jointed Rock Mass

2011 ◽  
Vol 90-93 ◽  
pp. 2033-2036 ◽  
Author(s):  
Jin Shan Sun ◽  
Hong Jun Guo ◽  
Wen Bo Lu ◽  
Qing Hui Jiang
Keyword(s):  
Rock Mass ◽  
Numerical Models ◽  
Jointed Rock ◽  
In Situ Stress ◽  
Jointed Rock Mass ◽  
Joint Orientation ◽  
Joint Spacing ◽  
Factors Affecting ◽  
Dip Angle

The factors affecting the TBM tunnel behavior in jointed rock mass is investigated. In the numerical models the concrete segment lining of TBM tunnel is concerned, which is simulated as a tube neglecting the segment joint. And the TBM tunnel construction process is simulate considering the excavation and installing of the segment linings. Some cases are analyzed with different joint orientation, joint spacing, joint strength and tunnel depth. The results show that the shape and areas of loosing zones of the tunnel are influenced by the parameters of joint sets and in-situ stress significantly, such as dip angle, spacing, strength, and the in-situ stress statement. And the stress and deformation of the tunnel lining are influenced by the parameters of joint sets and in-situ stress, too.

Experimental Research on Failure Modes of Specimen Containing Non-Coplanar Joints

2013 ◽  
Vol 779-780 ◽  
pp. 332-336
Author(s):  
Ping Cao ◽  
Wen Cheng Fan ◽  
Ke Zhang
Keyword(s):  
Shear Strength ◽  
Failure Mode ◽  
Failure Modes ◽  
Cement Mortar ◽  
Failure Process ◽  
Jointed Rock ◽  
Important Relationship ◽  
Initial Setting ◽  
Series Of Experiments ◽  
Dip Angle

To study the failure mechanism and failure mode of jointed rock under compressive-shear, many rock-like material specimens containing non-coplanar joints were made and a series of experiments were carried out. In the experiments, mica sheets were used as joint fillings, cement mortar was selected as rock-like material. Joints were made by inserting the mica sheet in cement mortar before initial setting. Mica sheets were left down as joint fillings. The results of experiments show that the dip angles of major joint have important influence on the failure mode of specimens. And the emerging position of wing cracks which exist in the prophase of specimens failure process changes with the dip angle. The shear strength of specimens has an important relationship with the dip angle of major joints. The smallest shear strength happens in the specimen with a joint angle of 15°, while the biggest value happens in 60°.

scholarly journals Model Test Study on the Anisotropic Characteristics of Columnar Jointed Rock Mass

Symmetry ◽  
2020 ◽  
Vol 12 (9) ◽  
pp. 1528
Author(s):  
Zhende Zhu ◽  
Xiangcheng Que ◽  
Zihao Niu ◽  
Wenbin Lu
Keyword(s):  
Rock Mass ◽  
Failure Modes ◽  
Engineering Application ◽  
Jointed Rock ◽  
Structural Features ◽  
Jointed Rock Mass ◽  
Hexagonal Prism ◽  
Compression Tests ◽  
Test Study ◽  
Columnar Jointed Rock Mass

Because of its special structure, the anisotropic properties of columnar jointed rock mass (CJRM) are complicated, which brings difficulty to engineering construction. To comprehensively study the anisotropic characteristics of CJRM, uniaxial compression tests were conducted on artificial CJRM specimens. Quadrangular, pentagonal and hexagonal prism CJRM models were introduced, and the dip direction of the columnar joints was considered. Based on the test results and the structural features of the three CJRM models, the deformation and strength characteristics of CJRM specimens were analyzed and compared. The failure modes and mechanisms of artificial specimens with different dip directions were summarized in accordance with the failure processes and final appearances. Subsequently, the anisotropic degrees of the three CJRM models in the horizontal plane were classified, and their anisotropic characteristics were described. Finally, a simple empirical expression was adopted to estimate the strength and deformation of the CJRM, and the derived equations were used in the Baihetan Hydropower Station project. The calculated values are in good agreement with the existing research results, which reflects the engineering application value of the derived empirical equations.

scholarly journals Study of the Failure Mode of a Jointed Rock Mass due to a Stress Wave

2021 ◽  
Vol 2021 ◽  
pp. 1-12
Author(s):  
Xi Kun Qian ◽  
Cong Cong Li
Keyword(s):  
Rock Mass ◽  
Failure Mode ◽  
Dynamic Loading ◽  
Stress Wave ◽  
Static Loading ◽  
Failure Process ◽  
Jointed Rock ◽  
Jointed Rock Mass ◽  
Dynamic Failure ◽  
Shear Cracks

The mechanical response and failure process of a jointed rock mass subjected to dynamic loading is very important for the safety and stability of rock engineering projects. In this study, we use RFPA2D-Dynamic, a rock dynamic failure process analysis platform, to establish a two-dimensional impact model of a jointed rock mass to analyze the mechanism of crack propagation in a jointed rock mass with preexisting cracks under dynamic loading. We discuss the influence of the stress wavelength and precrack inclination on the dynamic failure process and mode of the rock mass and compare this failure process with the failure model under static loading. The results show that the dynamic failure process and crack initiation type of a jointed rock mass are closely related to the stress wavelength. For a given peak, as the stress wavelength increases, the failure mode changes from local cracking that occurs above the precracks to a global instability caused by wing cracks. Meanwhile, as the wavelength increases, the shear cracks and mixed tensile-shear cracks generated at the two ends of the precracks are replaced by tensile cracks. The precrack inclination on a jointed rock mass mainly affects the strength of the jointed rock mass and the final failure mode. Specifically, when the joint inclination is small, the rock mass is severely damaged in the region above the precracks because the stress wave forms a region of cracks with a concentrated distribution. As the joint inclination increases, the damaged region becomes larger while the rock mass is less prone to failure; the strength of the rock mass gradually increases, and the wing cracks produced at the two ends of precracks propagate toward the upper and lower ends of the rock mass. However, when the stress wavelength is small, the precracks of different inclinations form cracks in the region above the precracks with a length similar to the precracks. For this condition, the propagation of the cracks is mainly controlled by the stress wavelength, while the influence of the inclination of the precracks is not significant. There is a significant difference between the failure modes of a rock specimen under dynamic loading or static loading because the stress wave produces a reflected tension wave in the direction parallel to the wave attack of the joint plane, which leads to spalling, while the wing cracks are more likely to occur under static loading.

scholarly journals Crack Initiation, Propagation, and Failure Characteristics of Jointed Rock or Rock-Like Specimens: A Review

2019 ◽  
Vol 2019 ◽  
pp. 1-31 ◽  
Author(s):  
Ri-hong Cao ◽  
Ping Cao ◽  
Hang Lin ◽  
Xiang Fan ◽  
Chunyang Zhang ◽  
...  
Keyword(s):  
Rock Mass ◽  
Crack Initiation ◽  
Failure Modes ◽  
Failure Process ◽  
Jointed Rock ◽  
Jointed Rock Mass ◽  
Failure Behavior ◽  
Failure Characteristics ◽  
Deformation And Failure ◽  
Natural Rock

Rock masses are heterogeneous materials containing a large number of discontinuities, and the failure of the natural rock mass is induced by the crack propagation and coalescence of discontinuities, especially for the rock mass around tunnel or underground space. Because the deformation or failure process of jointed rock mass exhibits strongly nonlinear characteristics, it is also very difficult to predict the strength and failure modes of the rock mass. Therefore, it is very necessary to study the failure mechanisms of jointed rock mass under different stress conditions. Apart from the stress condition, the discontinuities geometry also has a significant influence on the mechanical behavior of jointed rock mass. Then, substantial, experimental, and numerical efforts have been devoted to the study of crack initiation, propagation, and coalescence of rock or rock-like specimens containing different kinds of joints or fissures. The purpose of this review is to discuss the development and the contribution of the experiment test and numerical simulation in failure behavior of jointed rock or rock-like specimens. Overall, this review can be classified into three parts. It begins by briefly explaining the significance of studying these topics. Afterwards, the experimental and numerical studies on the strength, deformation, and failure characteristics of jointed rock or rock-like materials are carried out and discussed.

scholarly journals A Study on Triaxial Unloading Test of Columnar-Jointed-Rock-Mass-Like Material with AW Velocity Analysis

2020 ◽  
Vol 2020 ◽  
pp. 1-14
Author(s):  
Jianrong Xu ◽  
Hao Li ◽  
Qingxiang Meng ◽  
Weiya Xu ◽  
Mingjie He ◽  
...  
Keyword(s):  
Rock Mass ◽  
Volume Expansion ◽  
Failure Modes ◽  
Jointed Rock ◽  
Jointed Rock Mass ◽  
Stress Strain ◽  
Deformation And Failure ◽  
Failure Patterns ◽  
Confining Pressures ◽  
Columnar Jointed Rock Mass

To study the strength, deformation, and failure patterns of columnar-jointed-rock-mass (CJRM) under unloading conditions, triaxial unloading tests using the CJRM-like material samples are carried out, and acoustic wave (AW) velocities are simultaneously recorded. Based on stress-strain curves and AW velocities under different initial confining pressures and unloading rates, the stress-strain characteristics, strength, and deformation parameters, failure modes, and variation of the AW velocity are analyzed. Test results show that the CJRM may exhibit intense volume expansion during the unloading process. With the increase of the unloading and its rate, the volume expansion becomes more serious and the failure mode becomes more complicated. By reducing the unloading (rate), a phenomenon of unloading relaxation is observed and the quality of CJRM is significantly improved. The AW velocity of CJRM shows a strong correlation with the volume strain, which verifies the effectiveness of applying AW velocity for assessing the rock quality. It is hoped that the research results may provide a reference for the construction and operation of the Baihetan Hydropower Project.

scholarly journals Numerical Analysis of the Mechanical Behavior and Failure Mode of Jointed Rock under Uniaxial Tensile Loading

2020 ◽  
Vol 2020 ◽  
pp. 1-13
Author(s):  
Yang Zhao ◽  
Yongning Wu ◽  
Qing Xu ◽  
Lishuai Jiang ◽  
Wanpeng Huang ◽  
...  
Keyword(s):  
Mechanical Behavior ◽  
Failure Mode ◽  
Failure Modes ◽  
Tensile Tests ◽  
Jointed Rock ◽  
Rock Joints ◽  
Tensile Failure ◽  
Uniaxial Tensile ◽  
Direct Tensile ◽  
Rock Specimens

In the field of rock engineering, tensile failure is one of the most significant failure modes due to the presence of joints/fractures. However, due to the limitations of current laboratory testing, it is difficult to carry out direct tensile tests on jointed rock specimens in the laboratory. To study the effect of joints on the mechanical behavior and failure mode of jointed rock specimens, a three-point modeling method that can consider arbitrarily arranged rock joints is deduced and applied to discrete element simulation. The effects of different joint angles (the inclination angle α, rotation angle β, and superimposed angle γ of α and β, where γ is the angle between the joint and horizontal plane), the density (n), and the rate of cutting area (RCA) of the specimen loading surface (LSS) on the tensile strength (σt), elastic modulus in tension (Et), and failure mode of the specimens were analyzed. The results show that the joint angle (considering α, β, and γ) and RCA have a significant effect on the resulting σt and failure mode, while n has a significant effect on Et. The failure mode of the specimen changes from tensile failure along the joint to direct tensile failure of the specimen as γ increases, and the mechanical behavior transitions from unstable to stable. In addition, the main influence of γ on the mechanical behavior of specimens is revealed, and the change process of the failure mode after the cutting of the LSS is analyzed. The present research can be utilized for multiple purposes, including the joint development of surrounding rock and failure dominated by tensile failure in underground engineering, especially for tunnels, roadways, chambers, and so forth.

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