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.

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.

Precise grading of surrounding rock based on the numerical calculation of the jointed rock mass

2022 ◽  
pp. 1-32
Author(s):  
Dan Huang ◽  
Xiao-Qing Li ◽  
Wen-Chao Song
Keyword(s):  
Rock Mass ◽  
Numerical Calculation ◽  
Calculation Method ◽  
Jointed Rock ◽  
Jointed Rock Mass ◽  
Surrounding Rock ◽  
Geological Survey ◽  
Survey Method ◽  
Synthetic Rock ◽  
Numerical Calculation Method

In this study, grading of surrounding rock was based on rock mass basic quality (BQ) values according to the specifications in China. Numerical approach was to construct synthetic rock mass (SRM) model to represent the jointed rock mass, and obtain the strength of the rock mass. It represented intact rock by the bonded particle model (BPM), and represent joint behaviour by the smooth joint model (SJM) to construct the discrete fracture network (DFN). In the Hongtuzhang Tunnel, the micro properties of granite cores with different weathered degrees were determined by the validation process, and the calculation representative elementary volume (REV) of surrounding rock was 15 m×15 m. Five slightly weathered, three slightly to moderately weathered, and two moderately weathered granite surrounding rock mass models were established based on the probability distribution of joint sets in each borehole, the conversion BQ value was acquired according by the calculated strength of rock mass model. It was discussed the differences of surrounding rock grades between the geological survey method and the numerical calculation method, and then found that the geological survey report is higher than the numerical calculation method predicted. And the numerical calculation is consistent with the actual excavation of rock mass at borehole A1388.

scholarly journals The Method of Determining Excavation Damaged Zone by Acoustic Test and the Application in Engineering Cases

2021 ◽  
Vol 2021 ◽  
pp. 1-13
Author(s):  
Qian-Cheng Sun ◽  
Hao-Sen Guo ◽  
Zhi-Hua Xu ◽  
Yue Liu ◽  
Xiao Xu
Keyword(s):  
Rock Mass ◽  
Damage Evolution ◽  
Hard Rock ◽  
Damage Zone ◽  
Jointed Rock ◽  
Jointed Rock Mass ◽  
Surrounding Rock ◽  
Excavation Damaged Zone ◽  
Damaged Zone ◽  
Columnar Jointed Rock Mass

It is very important to accurately determine the depth of excavation damaged zone for underground engineering excavation and surrounding rock stability evaluation, and it can be measured by acoustic test, but there is no quantitative method for analysis of the results, and it relies heavily on the experience of engineers, which leads to the low reliability of the results and also limits the application of the acoustic method. According to substantial field test data and the feedback of surrounding rock support parameters, the boundary method is proposed to determine the depth of excavation damaged zone in surrounding rock based on the relation between the ultrasonic velocity of measured point and the background wave velocity of rock mass. When the method is applied to the columnar jointed rock mass of Baihetan and the deep-buried hard rock of Jinping, the excavation damaged zone was well judged. The results in the Baihetan project show that the proposed method of determining excavation damage zone by the acoustic test can well demonstrate the anisotropy characteristics of the columnar jointed rock mass, and the damage evolution characteristics of jointed rock mass at the same position can also be obtained accurately. Moreover, the method also can accurately reveal the damage evolution process of the deep-buried hard rock under the condition of high ground stress, which proved the applicability of this method in jointed or nonjointed rock masses.

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.

Displacement Back Analysis Research on Bolt-Grouting Supporting Parameter of Rock Mass in Jointed Rock Roadway

2004 ◽  
Vol 261-263 ◽  
pp. 1563-1568
Author(s):  
Le Wen Zhang ◽  
Shu Chen Li ◽  
Shu Cai Li
Keyword(s):  
Rock Mass ◽  
Mass Parameter ◽  
Back Analysis ◽  
Jointed Rock ◽  
Singular Value ◽  
Surrounding Rock ◽  
Elastic Model ◽  
Rock Stability ◽  
The Stability ◽  
Rock Roadway

The method of bolt-grouting supporting, grouting into surrounding rock mass by bolts in jointed rock mass roadway, is obtained wide application. However, it is difficult to determine rock mass parameter of bolt-grouting supporting. This paper begins with the displacement, which is measured easily in practice. The method of back analysis is adopted to calculate the equivalent mechanics parameters of bolt-grouting rock mass. In process of back analysis three mechanics models is supposed which are homogeneous elastic model, inhomogeneous elastic model and elastic-plastic model and corresponding algorithm is established. What's more, this paper discusses the stability of inverse algorithm and copes the problem of back analysis parameter probably instable with QR decomposed algorithm and singular value decomposed algorithm, which will be a theoretical base to determine the mechanics parameter of bolt-grouting supporting rock mass and to estimate the surrounding rock stability. In a word, the method is established to estimate mechanics parameters of bolt-grouting jointed surrounding rock mass, and some significant results are obtained, which are of reference for actual project.

scholarly journals A Model of Anisotropic Property of Seepage and Stress for Jointed Rock Mass

2013 ◽  
Vol 2013 ◽  
pp. 1-19 ◽  
Author(s):  
Pei-tao Wang ◽  
Tian-hong Yang ◽  
Tao Xu ◽  
Qing-lei Yu ◽  
Hong-lei Liu
Keyword(s):  
Rock Mass ◽  
Stress Field ◽  
Underground Mining ◽  
Principal Direction ◽  
Water Pressure ◽  
Jointed Rock ◽  
Jointed Rock Mass ◽  
Surrounding Rock ◽  
Metal Mine ◽  
Roadway Stability

Joints often have important effects on seepage and elastic properties of jointed rock mass and therefore on the rock slope stability. In the present paper, a model for discrete jointed network is established using contact-free measurement technique and geometrical statistic method. A coupled mathematical model for characterizing anisotropic permeability tensor and stress tensor was presented and finally introduced to a finite element model. A case study of roadway stability at the Heishan Metal Mine in Hebei Province, China, was performed to investigate the influence of joints orientation on the anisotropic properties of seepage and elasticity of the surrounding rock mass around roadways in underground mining. In this work, the influence of the principal direction of the mechanical properties of the rock mass on associated stress field, seepage field, and damage zone of the surrounding rock mass was numerically studied. The numerical simulations indicate that flow velocity, water pressure, and stress field are greatly dependent on the principal direction of joint planes. It is found that the principal direction of joints is the most important factor controlling the failure mode of the surrounding rock mass around roadways.

A New Criterion for Stability Analysis of Tunnel Surrounding Rock-Support Structure Based on the Convergence-Confinement Method

2012 ◽  
Vol 629 ◽  
pp. 427-432
Author(s):  
Yong Kang ◽  
Bo Long Chai ◽  
Xiao Chuan Wang ◽  
Deng Li
Keyword(s):  
Stability Analysis ◽  
Surrounding Rock ◽  
Geological Condition ◽  
Rock Support ◽  
Support Structure ◽  
Weak Zone ◽  
Deformation And Failure ◽  
True Value ◽  
The Stability ◽  
Ultimate Displacement

In the decision making of tunnel excavation and support scheme, stability analysis of surrounding rock-support structure is an essential link. Especially in fractured weak zone under complex geological condition, accurately measuring the deformation of support structure has an important significance for fast and safe construction. Based on the application of convergence confinement principle in judging tunnel deformation, this paper presented a new idea of using the ultimate displacement of tunnel initial support to analyze the stability of tunnel surrounding rock-support structure. Then, with a full investigation on the deformation and failure characteristics of highway tunnel surrounding rock at fractured weak zone, the ultimate displacement was got by using methods of numerical calculation and site monitoring measurement. Finally, the stability analysis of support structure in Zhongxing Tunnel was done. It can be arrived that there is a certain gap between true value u and measured value um of surrounding rock deformation. If the measuring points are installed after three excavation cycle, u is approximately equal to 1.6 um. then, based on the analysis of numerical simulation results and monitoring data of Zhongxing Tunnel, the paper indicated that the top and spring of arch are risk regions, reserved deformation of fractured weak zone is not enough, it should be adjusted from 10cm to 20cm.

scholarly journals A Strain-Softening Constitutive Model of Heterogeneous Rock Mass Considering Statistical Damage and Its Application in Numerical Modeling of Deep Roadways

2019 ◽  
Vol 11 (8) ◽  
pp. 2399 ◽  
Author(s):  
Guang Li ◽  
Fengshan Ma ◽  
Gang Liu ◽  
Haijun Zhao ◽  
Jie Guo
Keyword(s):  
Rock Mass ◽  
Strain Softening ◽  
Mining Area ◽  
Jointed Rock ◽  
Simulation Software ◽  
Softening Behavior ◽  
Underground Caverns ◽  
Heterogeneous Rock ◽  
The Stability ◽  
Statistical Damage

During the construction of underground caverns, the stability of deep underground cavern excavation, which affects the safety and sustainable development of such projects, is a hot issue. First, based on the mechanical properties of surrounding rock in deep tunnels, the strain-softening behavior, damage, and heterogeneity of rock masses are analyzed. Then, a strain-softening model of heterogeneous jointed rock mass that considers statistical damage (SSD) is developed and implemented through FLAC3D simulation software. Finally, the SSD is applied to a deep roadway in the Jinchuan mining area, and a comparative analysis of the computation results of the Mohr–Coulomb (MC) model and the strain-softening (SS) model are carried out. The numerical results are compared with the field-monitoring results, which show that the SSD model simulated the behavior of the surrounding rocks well. The results show that the deformations of the roof and floor are larger, which may serve as a reference for the support pattern of deep roadways.

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.

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