scholarly journals Stability Analysis of Neighborhood Tunnels with Large Section Constructed in Steeply Jointed Rock Mass

2020 ◽  
Vol 2020 ◽  
pp. 1-14
Author(s):  
Aichen Zheng ◽  
Feng Huang ◽  
Zhengdong Tang ◽  
Zhaoyi He
Keyword(s):  
Rock Mass ◽  
Jointed Rock ◽  
Jointed Rock Mass ◽  
Field Observations ◽  
Large Section ◽  
Symmetrical Design ◽  
Rock Anchors ◽  
The Stability ◽  
The Right ◽  
Good Agreement

To investigate the instability of two neighborhood tunnels with large crossing section during the construction, the Tushan subway station was taken as study background, which was built in steeply jointed rock mass. Based on the excavation method called traditional double side drift, numerical simulations of four different face excavation sequences in the two neighborhood tunnels were conducted to optimize construction sequence to improve the stability during tunneling. The results show that first excavation of the right tunnel produced less deformation of the tunnels due to joints dip. The effects of rock mass discontinuities on the stability of the tunnels were studied through comparison between the real condition with joints and the assumed condition without joints. Furthermore, six initial supporting systems with different parameters were compared, and the field observations of deformations along tunnel profile show good agreement with the numerical results. Based on the numerical simulation, the length of rock anchors could be designed asymmetrically, which is more economical than the symmetrical design. The optimized thickness of shot concrete and spacing of steel sets was 35 cm and 60 cm, respectively.

scholarly journals Numerical Simulation of Stress Arching Effect in Horizontally Layered Jointed Rock Mass

Symmetry ◽  
2021 ◽  
Vol 13 (7) ◽  
pp. 1138
Author(s):  
Xiao Huang ◽  
Huaining Ruan ◽  
Chong Shi ◽  
Yang Kong
Keyword(s):  
Rock Mass ◽  
Pressure Coefficient ◽  
Jointed Rock ◽  
Jointed Rock Mass ◽  
Surrounding Rock ◽  
Beam Structure ◽  
Underground Engineering ◽  
Joint Spacing ◽  
Arching Effect ◽  
The Stability

Stress arching effect during the excavation of broken surrounding rock in underground engineering has an important influence on the stability of surrounding rock after underground excavation. To determine the stress arching effect in horizontally layered jointed rock mass, the stress arching characteristics of surrounding rock mass after excavation is analyzed in this study by using a series of numerical tests. The formation mechanism of stress arch is revealed through a comparison of the stress characteristics of a voussoir beam structure and theoretical analysis of multi-block mechanical relationship of jointed rock mass. The method for determining the boundaries of a stress arching zone is proposed, and the influence of various factors on a stress arch is further discussed. Results show that after the excavation of horizontally layered jointed rock mass, the stress arch bunch (SAB) is formed in the lower strata above the cavern, and the global stress arch (GSA) is formed in the higher strata, both of which are symmetrical arch stress patterns. The SAB is the mechanical manifestation of the voussoir beam structure formed by several low-level sandstone layers, and the GSA is caused by the uneven displacement between blocks. Compared with the GSA, the SAB is more sensitive to various influencing factors. The extent of stress arching zone decreases with the increase of an internal friction angle of the joint, lateral pressure coefficient, and overburden depth. In addition, the joint spacing of rock strata is conducive to the development of a stress arch. Results can provide technical support for deformation control and the stability analysis of broken surrounding rock in underground engineering.

A Constitutive Model of Anchored Jointed Rock Mass and its Application

2008 ◽  
Vol 33-37 ◽  
pp. 657-662
Author(s):  
Xiao Jing Li ◽  
Wei Min Yang ◽  
Wei Shen Zhu ◽  
Shu Cai Li ◽  
Ai Hua Sun
Keyword(s):  
Numerical Simulation ◽  
Rock Mass ◽  
Constitutive Model ◽  
Damage Mechanics ◽  
Jointed Rock ◽  
Jointed Rock Mass ◽  
The Stability ◽  
Effective Reinforcement ◽  
Macroscopic Failure ◽  
Damage Equation

The jointed rock mass distributed in the nature widely and its mechanical characteristic influenced the stability of the rock engineering badly. The cracks propagated and coalesced each other and macroscopic failure happened. Bolts were a kind of effective reinforcement instrument and they could prevent the cracks from propagating. However, the anchoring mechanism of bolts was not realized clearly and their reinforcement could not be reflected effectively in the numerical simulation yet. Based on the damage mechanics, a constitutive relation and damage equation of anchored jointed rock mass were presented in this paper. With a project application, the model was proved to be feasible one.

scholarly journals Investigation of Deep Shaft-Surrounding Rock Support Technology Based on a Post-Peak Strain-Softening Model of Rock Mass

2021 ◽  
Vol 12 (1) ◽  
pp. 253
Author(s):  
Jianjun Zhang ◽  
Yang Wang ◽  
Baicong Yao ◽  
Dongxu Chen ◽  
Chuang Sun ◽  
...  
Keyword(s):  
Rock Mass ◽  
Strain Softening ◽  
Jointed Rock ◽  
Jointed Rock Mass ◽  
Surrounding Rock ◽  
Peak Strain ◽  
Rock Support ◽  
Support Structure ◽  
The Stability ◽  
Surrounding Rock Deformation

To control the large deformation that occurs in deep shaft-surrounding rock, the post-peak strain-softening characteristics of deep jointed rock mass are discussed in detail. An equivalent post-peak strain-softening model of jointed rock mass is established based on continuum theory and the geological strength index surrounding rock grading system, and numerical simulations are performed using FLAC3D software. The convergence-constraint method is used to analyze the rock support structure interaction mechanism. A composiste support technique is proposed in combination with actual field breakage conditions. During the initial support stage, high-strength anchors are used to release the rock stress, and high-stiffness secondary support is provided by well rings and poured concrete. This support technology is applied in the accessory well of a coal mine in Niaoshan, Heilongjiang, China. The stability of the surrounding rock support structure is calculated and analyzed by comparing the ideal elastic-plastic model and equivalent jointed rock mass strain-softening model. The results show that a support structure designed based on the ideal elastic-plastic model cannot meet the stability requirements of the surrounding rock and that radial deformation of the surrounding rock reaches 300 mm. The support structure designed based on the equivalent joint strain-softening model has a convergence rate of surrounding rock deformation of less than 1 mm/d after 35 days of application. The surrounding rock deformation is finally controlled at 140 mm, indicating successful application of the support technology.

The Research on the Calculation Methods and the Influential Factors Analysis of the Mechanical Joint Persistence Ratio of Jointed Rock Mass

2012 ◽  
Vol 424-425 ◽  
pp. 476-479
Author(s):  
Jian Yun Chen ◽  
Xi Wei Hu
Keyword(s):  
Rock Mass ◽  
Jointed Rock ◽  
Jointed Rock Mass ◽  
Influential Factors ◽  
Calculation Methods ◽  
Mechanical Joint ◽  
Factors Analysis ◽  
The Monte Carlo Method ◽  
Discontinuous Joints ◽  
The Stability

The paper presents a method used to model rock as continuous media with discontinuous joints. The Monte-Carlo method is employed in simulating the joint network of jointed rock mass based on certain principles, and the calculation method on the mechanical persistence ratio is studied, furthermore, some research on the influential factors on the persistence ratio is performed, and the values of some empirical parameters are obtained, which assured the stability of the results.

DDARF Analysis on Shear Tests of Jointed Rock Mass

2013 ◽  
Vol 353-356 ◽  
pp. 507-510 ◽  
Author(s):  
Shuai Guo ◽  
Wei Shen Zhu ◽  
Yong Li ◽  
Chao Jia
Keyword(s):  
Numerical Simulation ◽  
Rock Mass ◽  
Jointed Rock ◽  
Jointed Rock Mass ◽  
Model Tests ◽  
Shear Tests ◽  
Strain Stress ◽  
Good Agreement

Referring to the previous shearing model tests on intermittence jointed rock mass, DDARF method was adopted to conduct the corresponding numerical simulation. It could be concluded from the cracking failure phenomena that the results of the numerical simulation and the tests were in good agreement. Then the intermittence joints were arranged as en echelon and different cracking failure phenomena, peak shear strengths and strain-stress relationships were also obtained.

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