scholarly journals Research on the Strength Characteristics and Crack Propagation Law of Noncoplanar Nonthrough Jointed Rock Mass by PFC2D

2021 ◽  
Vol 2021 ◽  
pp. 1-28
Author(s):  
Qingzhi Chen ◽  
Yuanming Liu ◽  
Shilong Mei ◽  
Kai Cao ◽  
Bin Du ◽  
...  
Keyword(s):  
Rock Mass ◽  
Numerical Models ◽  
Jointed Rock ◽  
Jointed Rock Mass ◽  
Strength Characteristics ◽  
Particle Flow Code ◽  
Direct Shear ◽  
Direct Shear Tests ◽  
Relief Angle ◽  
Propagation Law

In this study, five groups of numerical models with different conditions were established by using PFC2D (particle flow code) to simulate the direct shear tests of noncoplanar nonthrough jointed rock mass. It is proved that normal stress and shear rate, as well as the connectivity rate, relief angle, and inclination angle of joints, have significant influence on the strength characteristics, number of cracks, and the stress of the rock mass according to measurement taken at five different measurement circles in the rock mass. Moreover, it is determined that in the process of shearing, no matter which group of tests are conducted, the number of cracks in the rock mass caused by tension is far more than that caused by the shear action. In other words, the failure of rock mass with different planes and discontinuous joints is mainly caused by the tension in the process of the direct shear test.

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 Strength Characteristics of Nonpenetrating Joint Rock Mass under Different Shear Conditions

2020 ◽  
Vol 2020 ◽  
pp. 1-13
Author(s):  
Qingzhi Chen ◽  
Yuanming Liu ◽  
Shaoyun Pu
Keyword(s):  
Rock Mass ◽  
Normal Stress ◽  
Direct Shear Test ◽  
Shear Test ◽  
Jointed Rock ◽  
Jointed Rock Mass ◽  
Strength Characteristics ◽  
Triaxial Tests ◽  
Direct Shear ◽  
Rock Specimens

The mechanical property of jointed rock mass is an important factor to be considered in the analysis, evaluation, and design of actual rock engineering. The existence of joints threatens the stability and safety of underground engineering projects built in the rock mass. In order to study the change of mechanical properties and strength characteristics of nonpenetrating jointed rock mass under different test conditions, direct shear tests and triaxial tests were carried out. Direct shear tests under different normal stresses were carried out for nonpenetrating jointed rock mass to prepare specimens for triaxial tests. Then, triaxial tests were carried out to study the change of mechanical properties and strength characteristics of the nonpenetrating jointed rock mass. In the direct shear test part, the greater the normal stress is, the stronger the shear strength and the more serious the shear failure would be. The main conclusions are as follows: (1) the strength of rock mass would increase with the increase of confining pressure for those rock specimens with same degrees of shear after the direct shear test; (2) for rock specimens with different degrees of shear after the direct shear test, if the shearing degree of the rock specimen was greater, the strength of the rock specimen would be lower in the triaxial test; (3) for rock specimens with the same damage degree after direct shear test, the greater the normal stress in direct shear test is, the smaller the peak axial pressure would be in the triaxial test; (4) if the specimen was sheared under higher normal stress in direct shear test, the cohesion of it would be lower and the internal friction angle would be larger. For the specimens under the same normal stress, if the shear failure of one specimen was more serious, the cohesion of it would be smaller and the internal friction angle would be larger.

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.

scholarly journals Generation of Numerical Models of Anisotropic Columnar Jointed Rock Mass Using Modified Centroidal Voronoi Diagrams

Symmetry ◽  
2018 ◽  
Vol 10 (11) ◽  
pp. 618 ◽  
Author(s):  
Qingxiang Meng ◽  
Long Yan ◽  
Yulong Chen ◽  
Qiang Zhang
Keyword(s):  
Rock Mass ◽  
Coefficient Of Variation ◽  
Numerical Models ◽  
Jointed Rock ◽  
Field Investigation ◽  
Jointed Rock Mass ◽  
Natural Fracture ◽  
Polycrystalline Materials ◽  
High Symmetry ◽  
Columnar Jointed Rock Mass

A columnar joint network is a natural fracture pattern with high symmetry, which leads to the anisotropy mechanical property of columnar basalt. For a better understanding the mechanical behavior, a novel modeling method for columnar jointed rock mass through field investigation is proposed in this paper. Natural columnar jointed networks lies between random and centroidal Voronoi tessellations. This heterogeneity of columnar cells in shape and area can be represented using the coefficient of variation, which can be easily estimated. Using the bisection method, a modified Lloyd’s algorithm is proposed to generate a Voronoi diagram with a specified coefficient of variation. Modelling of the columnar jointed rock mass using six parameters is then presented. A case study of columnar basalt at Baihetan Dam is performed to demonstrate the feasibility of this method. The results show that this method is applicable in the modeling of columnar jointed rock mass as well as similar polycrystalline materials.

scholarly journals A New Rock Joint Generation Method and Its Verification in PFC2D

2018 ◽  
Vol 2018 ◽  
pp. 1-16
Author(s):  
Lielie Li ◽  
Mingli Xiao ◽  
Cai Tan
Keyword(s):  
Shear Stress ◽  
Rock Joint ◽  
Fracture Network ◽  
Jointed Rock ◽  
Normal Direction ◽  
Particle Flow Code ◽  
Direct Shear ◽  
Direct Shear Tests ◽  
Mechanical Behaviours ◽  
Asperity Degradation

The first part of this paper presents the major drawbacks of the traditional methods for generating joints in Particle Flow Code 2D (PFC2D). Violent oscillations in the postpeak shear stress and shear-induced dilation in the normal direction occur in specimens generated by directly removing bonds in joints and using the discrete fracture network (DFN) method. The specimens generated by the additional wall method can be used to simulate realistic shear mechanical properties in the direct shear test, but it is difficult to achieve a uniform initial stress distribution within the specimen due to the constraint of particle motion. The second part of this paper explores an improved method to generate realistic joints based on the particle grouping technique and the smooth joint model, and the validity of this method is verified by a set of numerical direct shear tests. The numerical results show that the proposed joint generation method can effectively eliminate the oscillation of the postpeak shear stress and shear-induced dilation in the normal direction. In addition, the mechanical behaviours of the rough jointed rock mass correspond well with the theoretical results obtained from Patton’s and Barton’s models. The proposed model can also simulate the asperity degradation of rough jointed rock masses.

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