scholarly journals Experimental Study on Shear Failure Characteristics of Jointed Rock Mass Based on Direct Shear Tests and Digital Image Correction Techniques

2021 ◽  
Vol 2021 ◽  
pp. 1-16
Author(s):  
Fenhua Ren ◽  
Liwei Zhang ◽  
Xinghui Wu ◽  
Wensheng Liu
Keyword(s):  
Rock Mass ◽  
Shear Strain ◽  
Shear Failure ◽  
Jointed Rock ◽  
Image Correction ◽  
Shear Tests ◽  
Maximum Shear Strain ◽  
Direct Shear Tests ◽  
Discontinuous Joints ◽  
Dip Angle

The instability of rock engineering is normally dominated by the shear failure of rock mass. The dip angle of discontinuous planes widely existing in rock mass is a key parameter affecting the shear strength and failure mode of jointed rock. This paper aims to investigate the influence of discontinuous joints on the shear failure of rock. Direct shear tests are carried out on rock-like specimens with discontinuous joints in different dip angles. During the shear tests, the strain field is monitored in real-time by digital image correction (DIC) technology. Experimental results show that the shear strength, shear strain evolution, and failure mode for the jointed specimens are affected by the dip angles of the discontinuous joints. The maximum shear strain of specimens with joint angles of 45° and 75° increases gradually with the increase of shear loading. The maximum shear strain for the specimens with joint angles of 0°, 15°, 30°, 60°, and 90° increases sharply after the shear load reaches 80% of the peak load. When the joint inclination angle is less than 45°, the crack begins to expand from the joint tip and is interconnected to form a penetrating fracture. When the joint dip angle is greater than 45°, the cracks initiate at the joint tip and then propagate at different paths resulting in multistage shearing and crushing failure.

Evaluation of the anisotropy and directionality of a jointed rock mass under numerical direct shear tests

2017 ◽  
Vol 225 ◽  
pp. 29-41 ◽  
Author(s):  
Peitao Wang ◽  
Fenhua Ren ◽  
Shengjun Miao ◽  
Meifeng Cai ◽  
Tianhong Yang
Keyword(s):  
Rock Mass ◽  
Jointed Rock ◽  
Jointed Rock Mass ◽  
Direct Shear ◽  
Shear Tests ◽  
Direct Shear Tests

scholarly journals Experimental Investigation on Shear Failure Mechanism of Rock Mass with Intermittent Joints

2021 ◽  
Vol 2021 ◽  
pp. 1-10
Author(s):  
Minghui Ma ◽  
Fenhua Ren ◽  
Wensheng Liu
Keyword(s):  
Rock Mass ◽  
Shear Strain ◽  
Failure Mechanism ◽  
Shear Failure ◽  
Shear Fracture ◽  
Shear Loading ◽  
Surface Strain ◽  
Image Correlation ◽  
Maximum Shear Strain ◽  
Natural Rock

There are a large number of discontinuous weak planes distributed in the natural rock mass, which makes the sliding failure of rock mass along the intermittent structural plane very complex. To investigate the shear failure mechanism of rock mass with intermittent joints and study the influence of different joint heights on the shear failure mode of the rock mass, direct shear tests were carried out by presetting a series of jointed rock specimens with different undulating heights. During the shear loading, digital image correlation (DIC) technology was employed to monitor the surface strain field of the specimens in real time. The results show that the fluctuation height has a significant effect on the evolution of shear strain. With the increase of shear load, the maximum shear strain of the jointed specimens with different undulating heights first increases slowly and then increases rapidly. When the undulating height is 5 mm, the failure of the specimen is dominated by the rock sliding along prefabricated joints. When the undulating height is larger than 10 mm, the shear fracture of the rock becomes dominant. With the increase of the undulating height, more penetrating cracks perpendicular to the preexisting joints appear between the serrated surfaces, and the shear fracture phenomenon is more obvious.

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.

Study of Shear Constitutive Model for Schistose Rock Mass

2013 ◽  
Vol 838-841 ◽  
pp. 800-804
Author(s):  
Shang Ge Liu ◽  
Hua Xu ◽  
Jian Liu ◽  
Xiao Tao
Keyword(s):  
Rock Mass ◽  
Constitutive Model ◽  
Engineering Practice ◽  
Direct Shear ◽  
Shear Tests ◽  
Peak Displacement ◽  
Direct Shear Tests ◽  
Advantages And Disadvantages ◽  
Piecewise Exponential ◽  
Water Saturated

Based on the direct shear tests of schist and shale at dry and water-saturated states, combed with the advantages and disadvantages of models for rock mass and structure surface, we proposed shear stress-displacement constitutive model of schistose rock mass. The model is in the form of piecewise exponential function and its advantages are as follows: Piecewise function can reasonably describe the nonlinear pre-peak shear hardening and post-peak shear softening characteristics; Regard peak strength, peak displacement and residual strength as critical points, so it can accurately describe the strength characteristics of the material; The fitting degree is high with direct shear tests both at dry and water-saturated states; Only one parameter value is needed to obtain by fitting experimental curves while others are convenient to determine. All of those are benefit to applications in engineering practice.

scholarly journals Numerical Modeling on Dynamic Characteristics of Jointed Rock Masses Subjected to Repetitive Impact Loading

2021 ◽  
Vol 2021 ◽  
pp. 1-13
Author(s):  
Jie Liu ◽  
Yan-Bin Song ◽  
Yue-Mao Zhao
Keyword(s):  
Rock Mass ◽  
Impact Loading ◽  
Jointed Rock ◽  
Stress Waves ◽  
Rock Masses ◽  
Jointed Rock Masses ◽  
Numerical Tests ◽  
Repetitive Impact ◽  
Dip Angle ◽  
Energy Dissipated

A discrete element method code was used to investigate the damage characteristics of jointed rock masses under repetitive impact loading. The Flat-Joint Contact Model (FJCM) in the two-dimensional particle flow code (PFC2D) was used to calibrate the microparameters that control the macroscopic behavior of the rock. The relationship between macro- and microparameters by a series of uniaxial direct tension and compression numerical tests based on an orthogonal experimental design method was obtained to calibrate the microparameters accurately. Then, the Synthetic Rock Mass (SRM) method that incorporates joints into the calibrated particle model was used to construct large-scale jointed rock mass specimens, and the repetitive drop hammer impact numerical tests on SRM specimens with different numbers of horizontal joints and dip angle joints were carried out to study the damage evolution, stress wave propagation, and energy dissipation characteristics. The results show that the greater the number of joints, the greater the number of cracks generated, the greater the degree of damage, and the more energy dissipated for rock masses with horizontal joints. The greater the dip angle of joints, the less the number of cracks generated, the less the degree of damage, and the less energy dissipated for rock masses with different dip angles of joints. The impact-induced stress waves will be reflected when they encounter preexisting joints in the process of propagation. When the reflected stress waves meet with subsequent stress waves, the stress waves will change from compressional waves to tensile waves, producing tensile damage inside rock masses.

A damage constitutive model for rock mass with persistent joints considering joint shear strength

2015 ◽  
Vol 52 (8) ◽  
pp. 1136-1143 ◽  
Author(s):  
Hongyan Liu ◽  
Xiaoping Yuan
Keyword(s):  
Rock Mass ◽  
Constitutive Model ◽  
Failure Modes ◽  
Shear Failure ◽  
Jointed Rock ◽  
Joint Shear Strength ◽  
Rock Mass Strength ◽  
Damage Constitutive Model ◽  
Joint Shear ◽  
Set Up

Microcracks and joints, two types of flaws that appear in a rock mass, affect both the rock mass strength and deformability. A model that can simultaneously reflect the effect of these two types of flaws on the mechanical behavior of a rock mass with persistent joints is not yet available. This study focusses on a microcracked rock mass with persistent joints and establishes a mechanical model, accounting for the anisotropy in the rock mass strength and deformability induced by the existence of the joints. Firstly, the compound damage variable from the coupling macroscopic and mesoscopic flaws is deduced based on the Lemaitre strain equivalence hypothesis. Secondly, the corresponding damage constitutive model for a jointed rock mass is set up. Thirdly, the joint shear failure criterion is incorporated into the constitutive model to extend the model. Finally, the results of the calculation examples show that the existence of the joint will reduce the strength, enlarge the deformability, and lead to anisotropy of the rock mass. A series of calculation examples and comparisons validate that the proposed model is capable of presenting the joint-induced anisotropy in rock mass strength and deformability, determining its possible failure modes, and reasonably simulating its complete stress–strain relationship.

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