A theoretical method of mechanical analysis for a circular tunnel reinforced by fully grouted rock bolts

2021 ◽  
pp. 108128652110533
Author(s):  
Yijie Liu ◽  
Aizhong Lu ◽  
Xiangtai Zeng
Keyword(s):  
Rock Mass ◽  
Surrounding Rock ◽  
Force Balance ◽  
Shear Stresses ◽  
Circular Tunnel ◽  
Rock Bolts ◽  
Axial Forces ◽  
Concentrated Forces ◽  
Complete Contact ◽  
Grouted Rock Bolts

Analysis of the mechanical behavior of rock mass reinforced by fully grouted rock bolts is introduced based on the interaction between the rock mass and the bolts. The model is based on the following premises: (1) the elastic behavior of the rock mass and rock bolts; (2) the plane strain condition; (3) a deeply buried circular tunnel; (4) complete contact between the bolts and the surrounding rock, that is, they are bonded together; (5) the loads on the surrounding rock from the fully grouted rock bolts are replaced by innumerable concentrated forces along the longitudinal direction of the bolts. For this, the analytical radial displacement solution for a deeply buried circular tunnel subjected to concentrated forces at arbitrary points in surrounding rock is derived. As long as this displacement solution is integrated along the length direction of the bolt, the effect of the bolt on the surrounding rock can be obtained. According to the complete contact condition at the anchoring interface and the force balance condition of the bolts, under the action of the in situ stress, linear equations made up of shear stresses on the bolts are established, from which the distribution of shear stresses and axial forces along the bolts can be solved. Model simulations confirm the previous findings that each installed bolt has a pick-up length, an anchor length and a neutral point. Besides, the influence of the parameters of the rock bolts and the surrounding rock are discussed. The conclusion is consistent with the results of a practical project without adopting any empirical equations. The results of this method can provide a theoretical basis for the design and layout of rock bolts in underground caverns.

scholarly journals Primary Investigation on Equivalent Anchoring Method of Jointed Rock Mass Tunnel and Its Engineering Application

2020 ◽  
Vol 2020 ◽  
pp. 1-16
Author(s):  
Min Gao ◽  
Shanpo Jia
Keyword(s):  
Rock Mass ◽  
Three Dimensional ◽  
Engineering Application ◽  
Friction Angle ◽  
Jointed Rock ◽  
Jointed Rock Mass ◽  
Surrounding Rock ◽  
Rock Masses ◽  
Reinforcement Effect ◽  
Rock Bolts

Rock bolts, one of the main support structures of the tunnel, can improve the stress state and mechanical properties of the surrounding rocks. The rock bolts are simulated by bar or beam elements in present numerical calculations for most 2D tunnel models. However, the methods of simulating rock bolt in three-dimensional models are rarely studied. Moreover, there are too many rock bolts in the long-span tunnel, which are hardly applied in the 3D numerical model. Therefore, an equivalent anchoring method for bolted rock masses needs to be further investigated. First, the jointed material model is modified to simulate the anisotropic properties of surrounding rock masses. Then, based on the theoretical analysis of rock bolts in reinforcing mechanical properties of the surrounding rock masses, the equivalent anchoring method of the jointed rock mass tunnel is numerically studied. The equivalent anchoring method is applied to the stability analysis of a diversion tunnel in Western China. From the calculation results, it could be found that the reinforcement effect of rock bolts could be equivalently simulated by increasing the mechanical parameter value of surrounding rocks. For the jointed rock mass tunnel, the cohesion and internal friction angle of the surrounding rocks are improved as 1.7 times and 1.2 times of the initial value, which can simulate the reinforcement effect of rock bolts. Comparing with analytical results, the improved internal friction angle is nearly consistent with analytical result. The reinforcement effect of rock bolts is simulated obviously when the mechanical parameters of surrounding rocks are increased simultaneously. The engineering application shows that the equivalent anchoring method can reasonably simulate the effect of rock bolts, which can provide reference for stability analysis of three-dimensional tunnel simulations.

scholarly journals An Improved Stress and Strain Increment Approaches for Circular Tunnel in Strain-Softening Surrounding Rock Considering Seepage Force

2019 ◽  
Vol 2019 ◽  
pp. 1-17 ◽  
Author(s):  
Ling Wang ◽  
Jin-feng Zou ◽  
Yu-ming Sheng
Keyword(s):  
Rock Mass ◽  
Plastic Zone ◽  
Radial Displacement ◽  
Axisymmetric Problem ◽  
Strain Softening ◽  
Strain Increment ◽  
Surrounding Rock ◽  
Stress And Strain ◽  
Seepage Force ◽  
Circular Tunnel

Considering the effect of seepage force, a dimensionless approach was introduced to improve the stress and strain increment approach on the stresses and radial displacement around a circular tunnel excavated in a strain-softening generalized Hoek–Brown or Mohr–Coulomb rock mass. The circular tunnel can be simplified as axisymmetric problem, and the plastic zone was divided into a finite number of concentric rings which satisfy the equilibrium and compatibility equations. Increments of stresses and strains for each ring were obtained by solving the equilibrium and compatibility equations. Then, the stresses and displacements in softening zone can be calculated. The correctness and reliability of the proposed approach were performed by the existing solutions.

scholarly journals Study on strength parameters of rock mass with stochastic combination discontinuities and their application in a tunnel in China

2018 ◽  
Vol 10 (7) ◽  
pp. 168781401878208
Author(s):  
Jihong Wei ◽  
Jin Liu ◽  
Zezhuo Song ◽  
Yulong Zhu ◽  
Yuxia Bai
Keyword(s):  
Rock Mass ◽  
Numerical Test ◽  
Surrounding Rock ◽  
Discontinuous Deformation Analysis ◽  
Deformation Analysis ◽  
Test Case ◽  
Analysis Method ◽  
Circular Tunnel ◽  
Rock Stability ◽  
Discontinuous Deformation

The rock mass has special properties, such as inhomogeneity, anisotropy, discontinuity, and nonelastic, due to various internal or external stress in the process of its formation. In this study, similar materials are considered to simulate the rock mass and analyze the failure law using laboratory tri-axial tests based on the similarity principle. The rock mass and discontinuity are constituted in the process of model construction by considering the influence of the orientation, spacing, and number of discontinuity, respectively. Then, the influences of the orientation, spacing, number of discontinuity, and the combination of different discontinuous strength on rupture mechanism of the rock mass are analyzed by considering lots of numerical test schemes using the discontinuous deformation analysis method. Finally, considering water conveyance tunnel in Jurong Pumped Storage Power Station in China as a test case, the tunnel stability under different discontinuities combination is analyzed using discontinuous deformation analysis method. The influence of the optimal tunnel axis and tunnel shape on the stability of surrounding rock is studied by comparative analysis of surrounding rock stability under different tunnel axis and tunnel shapes. The stress concentration in case of the circular tunnel with corner is somehow less than that of the rectangular one.

Dynamical Response of Circular Tunnel with Steel Lining under the Action of Blasting Vibration

2010 ◽  
Vol 163-167 ◽  
pp. 4037-4042 ◽  
Author(s):  
Chang Ping Yi ◽  
Wen Bo Lu ◽  
Ling Feng ◽  
Gang Wang
Keyword(s):  
Rock Mass ◽  
Velocity Distribution ◽  
Expansion Method ◽  
Surrounding Rock ◽  
Vibration Velocity ◽  
Dynamical Response ◽  
Blasting Vibration ◽  
Circular Tunnel ◽  
Steel Lining ◽  
Wave Function Expansion Method

The wave function expansion method is used to analyze the interaction process of the blasting seismic wave and the adjacent circular tunnel with steel lining, the stress expression, displacement expression and vibration velocity expression of circular tunnel under the action of blasting vibration are deduced, the stress, displacement and vibration velocity distribution of surrounding rock mass and steel lining are presented under the definite condition. In terms of the stress and vibration velocity distribution and the tensile strength of the rock mass, the critical failure vibration velocity of surrounding rock mass is obtained.

Analysis of Monitoring and Measurement for Heishan Tunnel

2012 ◽  
Vol 446-449 ◽  
pp. 1645-1648
Author(s):  
Wen Ling Tian ◽  
Qi Li ◽  
Cheng Zhi Xiao
Keyword(s):  
Cross Sections ◽  
Surrounding Rock ◽  
Monitoring Data ◽  
Preliminary Design ◽  
Geological Condition ◽  
Monitoring Methods ◽  
Rock Bolts ◽  
Axial Forces ◽  
Study Results ◽  
Monitoring And Measurement

Abstract: For the purpose of stability of surrounding rocks of tunnel during the stage of construction and operation, a series of monitoring methods and measurement are carried out to investigate performance of Heishan tunnel through selecting 5 cross sections for monitoring. Based on the monitoring data, convergence around tunnel, displacement of different points of interior of surrounding rock, axial forces of rock bolts and pressure of surrounding rock are analyzed. The characteristics of selected cross sections are useful for engineers to optimize the preliminary design of tunnel. Furthermore, the study results can be used to guide the design, monitoring and construction for future tunnels with the similar geological condition.

scholarly journals Excavation Sequence and Surrounding Rock Mass Stability of Large-Scale Underground Engineering with 8 Tunnels

2020 ◽  
Vol 2020 ◽  
pp. 1-11
Author(s):  
Zhiqiang Zhang ◽  
Mingming He ◽  
Fangfang Chen ◽  
Ning Li
Keyword(s):  
Rock Mass ◽  
Plastic Zone ◽  
Large Scale ◽  
Mutual Influence ◽  
Surface Displacement ◽  
Surrounding Rock ◽  
In Situ Monitoring ◽  
Hydroelectric Power ◽  
Tunnel Face ◽  
Axial Forces

In some large-scale hydroelectric power projects, there are more than 3 tunnels that are too close to each other to eliminate the mutual influence during the excavation period, especially for large-scale tunnel groups. In this paper, aimed at analyzing the Bukun hydropower station consisting of 8 tunnels in Malaysia, the displacement, stress, and plastic zone of the surrounding rock mass are analyzed to study the effect of the excavation sequence on the stability of the surrounding rock mass for large-scale tunnel groups. On the one hand, the in situ monitoring of the surface displacement of the rock mass surrounding the tunnel using extensometers is performed to obtain the deformation characteristics on the excavation limit under the typical excavation sequence. On the other hand, a series of elastic-plastic 3D numerical experiments are carried out to explore the displacement characteristics, stability of the large-scale tunnel groups, and safety of the initial supporting system. The results show that the tendencies of the displacement increase corresponding to the tunnel face movement are similar for the three excavation sequences. The displacement under initial excavation sequence 2 (IES2) is the smallest among the three sequences; the area of the plastic zone under IES2 is the smallest among them; and the stresses in the shotcrete layer and axial forces in the rock bolt under the three excavation sequences are within the safety limitation. Initial excavation sequence 2 is an optimized excavation sequence, in which tunnels #1 and #5 are excavated first; after an advance of 3 times the diameter of the tunnel, tunnels #3 and #7 are excavated; tunnels #2 and #6 are excavated after an advance of 3 times diameters; and tunnels #4 and #8 are excavated after an advance of 3 times diameters.

Stability Analysis of Central Haulage in Baluba Copper Mine

2014 ◽  
Vol 638-640 ◽  
pp. 822-828
Author(s):  
Gao Hui Yao ◽  
Yi Ming Wang ◽  
Kai Jian Hu
Keyword(s):  
Rock Mass ◽  
Stability Analysis ◽  
Mathematical Modelling ◽  
Rock Bolts ◽  
The Poor ◽  
Support Measures ◽  
Cable Bolts ◽  
Induced Stresses ◽  
Protection Pillar ◽  
Grouted Rock Bolts

Site observations were conducted to investigate the reasons for the poor current rock-mass conditions being experienced in essential crosscuts, to provide recommendations for remedial support measures. Conceptual analyses of mining induced stresses within abutment pillars were undertaken using elastic analytical and mathematical modelling. The results showed that damage to the crosscuts is due to high mining-induced stresses, with the major stress probably acting vertically, the protection pillar for the 480 Level crosscut should be at least 100 m wide. The research demonstrated that only 2.4 m grouted rock-bolts and timber sets is not enough in these conditions, so the 480 Level and 580 Level central haulage should be re-supported with a combination of 4.0 m pre-tensioned cable-bolts, a 75 mm layer of steel mesh (or fibre) reinforced shotcrete, and even steel arch sets with lots of log.

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