scholarly journals Research on the Deformation Mechanism of Mining Roadway Stratiform Surrounding Rock with Nonuniform Stress Field

2021 ◽  
Vol 2021 ◽  
pp. 1-19
Author(s):  
Yongxin Sun
Keyword(s):  
Shear Stress ◽  
Plastic Zone ◽  
Maximum Shear Stress ◽  
Pressure Coefficient ◽  
High Stress ◽  
Surrounding Rock ◽  
Rock Joints ◽  
Instability Criterion ◽  
Structural Plane ◽  
Structure Plane

Aiming at the failure problems of mining roadway stratiform surrounding rock influenced by asymmetrical high stress, firstly, the rock instability conditions of different structural plane angles were summarized based on the mechanical model of rock joints and instability criterion. Secondly, stresses, plastic zone, and displacement of surrounding rock with different structural plane angles were calculated and analyzed with the theoretical calculation method or numerical simulation method, respectively. The distribution characteristics of plastic zone of surrounding rock under different influence factors are further studied, and the results show that the lateral pressure coefficient can change the size and shape of plastic zone at the same time. The damage mechanism was analyzed through the above study. Research studies show that the shear and tension failure area of plastic zone were directly determined by the maximum shear stress and the minimum principal stress. The effect of structure planes on stress has two sides, one to destroy the continuity and the other to strengthen discreteness and laddering nature. When the angle between maximum shear stress and structure plane increases, the extended mode and distribution pattern of plastic zone change substantially as well. The #15 haulage roadway is taken as engineering background, and the above research’s results are verified by the comprehensive analysis. The research results can enrich the butterfly plastic zone theory and provide the basis for roadway supporting design.

scholarly journals Analytical Solution of a Circular Opening considering Nonuniform Pressure and Its Engineering Application

2020 ◽  
Vol 2020 ◽  
pp. 1-13
Author(s):  
Peng Wu ◽  
Yanlong Chen ◽  
Liang Chen ◽  
Xianbiao Mao ◽  
Wei Zhang
Keyword(s):  
Analytical Solution ◽  
Plastic Zone ◽  
Young’S Modulus ◽  
Lateral Pressure ◽  
Young's Modulus ◽  
Pressure Coefficient ◽  
Surrounding Rock ◽  
Engineering Practice ◽  
Circular Opening ◽  
Lateral Pressure Coefficient

Based on the Mohr–Coulomb criterion, a new analytical solution of a circular opening under nonuniform pressure was presented, which considered rock dilatancy effect and elastic-brittle-plastic failure characteristics. In the plastic zone, the attenuation of Young’s modulus was considered using a radius-dependent model (RDM), and solution of the radius and radial displacement of plastic zone was obtained. The results show that many factors have important impact on the response of the surrounding rock, including lateral pressure coefficient, dilation coefficient, buried depth, and Young’s modulus attenuation. Under nonuniform pressure condition, the distribution of plastic zone and deformation around the opening show obvious nonuniform characteristic: with the increasing of lateral pressure coefficient, the range of plastic zone and deformation decrease gradually at side, while they increase at roof and floor, and the location of the maximum value of support and surrounding rock response curve transfers from side to roof. Based on the analytical results and engineering practice, an optimization method of support design was proposed for the circular opening under nonuniform pressure.

scholarly journals Research on the Reasonable Strengthening Time and Stability of Excavation Unloading Surrounding Rock of High-Stress Rock Mass

Geofluids ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-13
Author(s):  
Wensong Xu ◽  
Wentao Xu ◽  
Yunhai Cheng
Keyword(s):  
Rock Mass ◽  
Plastic Zone ◽  
Failure Process ◽  
High Stress ◽  
Stable State ◽  
Surrounding Rock ◽  
Triaxial Tests ◽  
Uniaxial Compression Test ◽  
True Triaxial ◽  
True Triaxial Tests

This study is aimed at better understanding the deformation and failure mechanism of surrounding rock during excavation unloading of a high-stress rock mass and determining the reasonable reinforcement time for the surrounding rock. To fulfill this aim, true triaxial tests were carried out on different loading and unloading paths during the unilateral unloading of a high-stress rock mass. The variational condition for minimization of plastic complementary energy is obtained, the optimal reinforcement time is determined, and the range of the plastic zone in the surrounding rock reinforced by anchor mesh-cable-grouting is compared and analyzed. The results are as follows: (1) Based on the Mohr-Coulomb yield criterion and the deformation reinforcement theory of surrounding rock, the stable state with the minimum reinforcement force is obtained. (2) After the true triaxial tests on the unilateral unloading of the third principal stress were carried out under different confining pressures, loading continued to be performed. Compared with rock failure without confining pressure, in the conventional uniaxial compression test, the failure of samples is dominated by composite splitting-shear failure; the unilateral unloading stress-concentration failure is a progressive failure process of splitting into plates followed by cutting into blocks and then the ejection of blocks and pieces. (3) The relationship between the time steps of the surrounding rock stability and the excavation distance is obtained. The supporting time can be divided into four stages: presupport stage, bolt reinforcement stage, anchor cable reinforcement stage, and grouting reinforcement stage. (4) In the range of within 5 m behind the tunneling face, the plastic zone of the surrounding rock with support is reduced by 7 m as compared with that with no support. In the range of over 5 m behind the tunneling face, the plastic zone of the roadway floor with support is reduced by 2.6 m as compared with that without support, and the deformation is reduced by 90%. These results can serve as a reference for controlling the behavior of surrounding rock during excavation unloading of high-stress rock masses.

Study on Stability of Layered Roof Surrounding Rock Reinforced by Anchor in Rectangular Roadway

2014 ◽  
Vol 638-640 ◽  
pp. 864-869
Author(s):  
Zhong Ming Zhao ◽  
Zhi Yuan Xi
Keyword(s):  
Shear Stress ◽  
Stress Distribution ◽  
Maximum Shear Stress ◽  
Maximum Tensile Stress ◽  
Surrounding Rock ◽  
Point Location ◽  
Anchor Cable ◽  
Mechanics Of Materials ◽  
Before And After ◽  
Dangerous Point

Under the assumptions of plane strain, vertical normal stress and shear stress distribution in surrounding rock of rectangular tunnels before and after installing anchor cable are studied. And according to the mechanics of materials, the formula of stress distribution in the roof is corrected. According to the corrected formula of the stress distribution, the dangerous points are found. And the dangerous point location does not change before and after installing anchor cable. It still locates in the middle and ends of roadway roof. Just the dangerous stress value decreases after installing anchor cable. There are the maximum tensile stress in the midpoint roof and the maximum shear stress on both ends of the roof.

scholarly journals The Criteria of Underground Rock Structure Failure and Its Implication on Rockburst in Roadway: A Numerical Method

2019 ◽  
Vol 2019 ◽  
pp. 1-12 ◽  
Author(s):  
Xiaofei Guo ◽  
Zhiqiang Zhao ◽  
Xu Gao ◽  
Zhenkai Ma ◽  
Nianjie Ma
Keyword(s):  
Stress Response ◽  
Plastic Zone ◽  
Large Scale ◽  
High Stress ◽  
Confining Pressure ◽  
Surrounding Rock ◽  
Failure Zone ◽  
Rock Structure ◽  
Large Scope ◽  
High Stress Level

Rockburst in roadway happened along with a large-scale destruction of the surrounding rock. To study the failure laws of the surrounding rock in the process of rockburst in roadway, the evolution behaviors of the plastic zone and the criteria of large-scope failure were studied by using FLAC numerical simulation. Meanwhile, the stress response laws of the plastic zone were studied by loading or unloading in a single direction. The results showed that, in the 20 MPa stress environment, large-scale failure zone would appear when the maximum confining pressure was loaded to 50 MPa or the minimum confining pressure was unloaded to 6 MPa. Loading in the direction of maximum confining pressure or unloading in the direction of minimum confining pressure, when the stresses reached a certain limit, could lead to a large-scale expansion to the failure zone of the surrounding rock a roadway. Meanwhile, the stress response of the plastic zone became more sensitive, which might easily trigger rockburst in roadway. In addition, two sine qua nonstress conditions for rockburst in roadway were determined: high stress ratio and high stress level. This might provide a theoretical basis for the stress source mechanism of roadway rockburst.

scholarly journals Geological Structural Surface Evaluation Model Based on Unascertained Measure

Geofluids ◽  
2019 ◽  
Vol 2019 ◽  
pp. 1-7 ◽  
Author(s):  
Kang Zhao ◽  
Qing Wang ◽  
Yajing Yan ◽  
Junqiang Wang ◽  
Kui Zhao ◽  
...  
Keyword(s):  
Evaluation Model ◽  
Measurement Theory ◽  
Geological Structure ◽  
Surrounding Rock ◽  
Engineering Practice ◽  
Gold Mine ◽  
Structural Plane ◽  
Rock Structure ◽  
Structure Plane ◽  
Structure Evaluation

The surrounding rock structure plane survey is the basis for mine geological structure evaluation and stability of surrounding rock. On the basis of the unascertained measurement theory and scanline method, the surrounding rock stability of the underground geological structure plane in Lingbao Luoshan Gold Mine is evaluated. First, according to the structural plane five grading standards, the 9 single-index measure functions are constructed. Second, the information entropy is used to determine the weight of each indicator. Accordingly, a multi-index comprehensive measure evaluation vector is established. Finally, the confidence level is used to determine the structural plane stability level. Results show that surrounding rock grades of middle sections of R1, R2, and R3 are Grades III, IV, and IV in Lingbao Luoshan Gold Mine, respectively. The evaluation grade is consistent with the actual situation of the mine, and strengthening the surrounding rock support for the middle sections of R2 and R3 is necessary. According to engineering practice, the evaluation model of the underground structure of metal mines established in this study has a practical value.

scholarly journals Numerical Simulation and Analysis of Tunnel Failure Mode by Stochastic Fracture Model

2021 ◽  
Vol 2021 ◽  
pp. 1-12
Author(s):  
Fukun Xiao ◽  
Lei Xu ◽  
Gang Liu ◽  
Zhiyuan Hou ◽  
Le Xing
Keyword(s):  
Numerical Simulation ◽  
Rock Burst ◽  
Monte Carlo Model ◽  
High Stress ◽  
Tectonic Stress ◽  
Simulation Software ◽  
Surrounding Rock ◽  
Structural Plane ◽  
Dip Angle ◽  
The Stability

The dip angle, length, spacing, and fracture distance of rock fissure affect the morphology of roadway after collapse. The numerical simulation software CDEM is used to simulate the morphology of roadway collapse. The Monte Carlo model is used to simulate different types of crack models in two-dimensional plane and generate different crack models. The effects of crack angle, crack length, fracture distance, and spacing on the deformation of surrounding rock are analyzed. The influence of different rock burst on the failure strap-fall modes of fissure roadway and roadway in different sections is analyzed, and the stability law of roadway is studied. Under the condition of high stress, the roadway shape has little influence on the distribution of the principal stress difference of surrounding rock, but the equivalent excavation radius determines the distribution of the plastic zone of surrounding rock. The larger the ineffective reinforcement zone is, the larger the deformation around the roadway will be. The decrease of the angle between the structural plane and the vertical stress increases the failure range of the roadway under the gravity burst pressure. Under the horizontal tectonic stress type rock burst, when the structural plane inclination angle is 0°, the two-sided caving body fills the roadway and the roof caving range becomes smaller.

Joint Controlling Effect on Stability of Surrounding Rock in Horseshoe-Shaped Underground Opening

2012 ◽  
Vol 170-173 ◽  
pp. 1643-1647 ◽  
Author(s):  
Lu Wang Chen ◽  
Yuan Qin ◽  
Jiang Hong Chen ◽  
Shi Lei Zhang
Keyword(s):  
Shear Stress ◽  
Plastic Zone ◽  
Cross Section ◽  
Inclination Angle ◽  
Surrounding Rock ◽  
Underground Opening ◽  
Controlling Effect ◽  
Stability Of Surrounding Rock ◽  
Vertical Displacements ◽  
Joint Inclination

This paper presents a numerical study on the mechanical behavior of the jointed rocks around the underground opening. By comparing different obliquities and the different locations of the joint, its controlling effect on stability of surrounding rock is evaluated in terms of the shear stress distribution, displacement distribution and the plastic zone pattern, which are induced by underground excavation. The results clearly indicate that, the maximum shear stress occurs mainly near the corner of the opening and the joint plane. When the joint inclination angle is less than 60º, the maximum vertical displacements occur where the joint locates near the skewback. Once the joint inclination angle reaches at 75º, the maximum vertical displacements occur where the joint is through the cross section of the underground opening. The plastic zone reaches minimum at the joint inclination angle of 45º where the joint locates either near the skewback or near spandrel of the opening, while it reaches minimum at the joint inclination angle of 60º where the joint cuts through the cross section of the opening.

PHOTOELASTIC STUDY ON THE MECHANICAL PROPERTIES OF FRACTAL ROCK JOINTS

Fractals ◽  
1996 ◽  
Vol 04 (04) ◽  
pp. 521-531 ◽  
Author(s):  
HEPING XIE ◽  
WEIHONG XIE ◽  
PENG ZHAO
Keyword(s):  
Mechanical Properties ◽  
Shear Stress ◽  
Shear Strength ◽  
Fractal Dimension ◽  
Maximum Shear Stress ◽  
Fractal Dimensions ◽  
Rock Joints ◽  
Peak Shear Strength ◽  
Joint Roughness ◽  
Contact Points

In this paper, the fractal rock joints are manufactured on the photoelastic material plate. Based on the visualized photoelastic experiments, the mechanical properties of the fractal joints with different roughness (different fractal dimensions) are investigated under uniaxial and shear compression. The research results indicate that the joint roughness (the fractal dimension of the joints) significantly influences the peak shear strength, the position of the maximum shear stress, and the number of contact points.

scholarly journals Laboratory Model Test Research on Mechanical Characteristics of Anchor in Loess Tunnel under the Action of Pull-Out Load

2021 ◽  
Vol 2021 ◽  
pp. 1-10
Author(s):  
Zhongming Su ◽  
Jianxun Chen ◽  
Yanbin Luo ◽  
Xin He
Keyword(s):  
Shear Stress ◽  
Model Test ◽  
Maximum Shear Stress ◽  
Test Chamber ◽  
Deformation Mode ◽  
Surrounding Rock ◽  
Laboratory Model ◽  
Engineering Practice ◽  
Distribution Law ◽  
Pull Out

The deformation mode of loess surrounding rock of anchor under the action of pull-out load and the shear stress distribution law of loess anchor and loess interface under the condition of different lengths anchor are studied by using the laboratory self-made model test chamber and micro anchor pullout instrument. A total of three tests are carried out for the selected test anchor. Three deformation modes of loess surrounding rock under the action of pull-out load are obtained according to the test results. It is proposed that the maximum shear stress of loess anchor under the action of pull-out load appears in the section 25 times the anchor diameter from the anchor head, and the shear stress in the middle and rear part of the anchor body can only be brought into full play when the length-to-diameter ratio of the anchor body is 110 or more. Based on the displacement solution of Mindlin problem, the drawn conclusion is compared with the theoretical solution of shear stress and axial force of loess anchor under the action of pull-out load. The results compared are basically consistent, indicating that the conclusion has strong engineering practice, which can provide technical basis for the design and optimization of the system anchor in the sidewall of loess tunnel.

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