scholarly journals Study on Deformation Mechanism and Supporting Countermeasures of Compound Roofs in Loose and Weak Coal Roadways

2020 ◽  
Vol 2020 ◽  
pp. 1-13
Author(s):  
Jianfeng Cui ◽  
Weijun Wang ◽  
Chao Yuan ◽  
Liming Cao ◽  
Yuning Guo ◽  
...  
Keyword(s):  
Field Application ◽  
Surrounding Rock ◽  
Main Body ◽  
Vicious Cycle ◽  
Rock Stress ◽  
Anchor Cable ◽  
Coal Roadway ◽  
Safe Control ◽  
Roadway Support ◽  
Surrounding Rock Stress

This paper considers the 333 return airway of the Gaokeng Coal Mine to analyze the deformation characteristics and failure mechanism of the surrounding rock of the composite roof for a loose and weak coal roadway. The reasons for the large deformation are explored and the superiority of the prestressed truss and anchor rope is compared to ordinary anchor cables from the perspective of mechanics to propose a targeted coal roadway support method. Sinking of the composite roof in the coal roadway is accompanied with a release and transfer of the surrounding rock stress. The pressure of the composite roof transfers to the roadway sides and intensifies the fracture process of the coal body. As a result, the ability to support the composite roof is weakened, and it further bends and sinks to form a vicious cycle that repeats itself. Therefore, the support of the composite roof in the coal roadway should consider the roof, roadway sides, and floor as a single unit to achieve the support goal of reinforcing the roadway sides and roof. Based on the above analysis, a comprehensive control technology with a truss and anchor rope is proposed as the main body and a bolt + anchor cable + metal network as the auxiliary. This technology can improve the integral bearing capacity of the composite roof, strengthen the roadway side structures, and reinforce the roadway sides and roof. Numerical simulation and field application results show that the support scheme can effectively realize safe control of the composite roof in coal roadways.

scholarly journals An Experimental Research on Surrounding Rock Unloading during Solid Coal Roadway Excavation

Geofluids ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-9
Author(s):  
Hongjun Guo ◽  
Ming Ji ◽  
Dapeng Liu ◽  
Mengxi Liu ◽  
Gaofeng Li ◽  
...  
Keyword(s):  
Energy Storage ◽  
Deformation Energy ◽  
Surrounding Rock ◽  
Dissipated Energy ◽  
Rock Stress ◽  
Deformation And Failure ◽  
Coal Roadway ◽  
Solid Coal ◽  
Unloading Rate ◽  
Surrounding Rock Stress

In order to further explore the deformation and failure essence of the deep coal body, based on the characteristics of surrounding rock stress adjustment before and after solid coal roadway excavation, an experiment of unloading confining pressure and loading axial pressure of the coal body was designed and conducted in this study. Based on test results, the failure mechanics and energy characteristics of the coal body were analyzed through experiments. Rapid unloading is considered a key factor contributing to lateral deformation and expansion failure, which exacerbates the deterioration of coal body and reduces the deformation energy storage capacity of coal. On the other hand, the larger loading rate tends to shorten the accumulation time of microcracks and cause damage to the coal body, resulting in strengthening the coal body and improving energy storage. Under the circumstance that the coal body is destroyed, the conversion rates of the internal deformation energy and dissipated energy are more significantly affected by unloading rate. The increasing unloading rate and rapid decreases in the conversion rate of deformation energy make the coal body more vulnerable to damage. Under the same stress conditions, the excavation unloading is more likely to deform, destroy, or even throw the coal than the experiment unloading. In order to reduce or avoid the occurrence of deep roadway excavation accidents, the understanding of the excavation unloading including possible influencing factors and the monitoring of the surrounding rock stress and energy during the excavation disturbance should be strengthened. It can be used as the basis for studying the mechanism of deformation and failure of coal and rock and dynamic disasters in deep mines, as well as the prediction, early warning, prevention, and control of related dynamic disasters.

Field Monitoring of Surrounding Rock Stress in Tunnel Construction

2012 ◽  
Vol 170-173 ◽  
pp. 1735-1739
Author(s):  
Ying Na Dong ◽  
Qiang Huang
Keyword(s):  
Spatial Effect ◽  
Field Monitoring ◽  
Surrounding Rock ◽  
Tunnel Construction ◽  
Rock Stress ◽  
Vibrating Wire ◽  
Stress Variation ◽  
Stress Changes ◽  
Tunnel Diameter ◽  
Surrounding Rock Stress

The surrounding rock stress field monitor has been done in excavation by vibrating wire transducer. The field monitoring data are compared with numerical simulation results. The result shows: Vibrating wire transducer can record the stress variation of surrounding rock and support. Surrounding rock stress changes violently at every excavation step, such as lower bench excavation, the stress variation is mainly controlled by the spatial effect. When the distance from excavation face to the monitoring section is more than a tunnel diameter, the rock stress variation is mainly affected by time and it is relatively smooth and continuous.

scholarly journals Study on Stability of Round Tunnel Surrounding Rock

2018 ◽  
Vol 175 ◽  
pp. 04016
Author(s):  
NIU Yan ◽  
Ji Yafei ◽  
Wang Zhao
Keyword(s):  
Evaluation Criteria ◽  
Surrounding Rock ◽  
Rock Stress ◽  
Stress Release ◽  
Circular Tunnel ◽  
Tunnel Excavation ◽  
Finite Element Software ◽  
Rock Stability ◽  
The Stability ◽  
Surrounding Rock Stress

Tunnel excavation will lead to the immediate surrounding rock unloading caused by the surrounding rock stress release, the stability of the surrounding rock have a certain impact. In this paper, finite element software ANSYS and finite difference software FLAC3D are used to simulate the excavation and lining process of circular tunnel. The influence of excavation on the rock stability around circular tunnel is analyzed, and the effect of applying lining on the stability of surrounding rock is analyzed. Evaluation criteria selection hole displacement, stress and plastic area of three factors.

scholarly journals Stress Evolution Law of Surrounding Rock with Gob-Side Entry Retaining by Roof Cutting and Pressure Release in Composite Roof

2020 ◽  
Vol 2020 ◽  
pp. 1-15
Author(s):  
Yong Zhang ◽  
Huichen Xu ◽  
Peng Song ◽  
Xiaoming Sun ◽  
Manchao He ◽  
...  
Keyword(s):  
Stress Concentration ◽  
Surrounding Rock ◽  
Rock Stress ◽  
Dynamic Adjustment ◽  
Pressure Relief ◽  
Middle Point ◽  
Pressure Release ◽  
Whole Process ◽  
Working Face ◽  
Surrounding Rock Stress

The stress concentration of gob-side entry surrounding rock is a hot topic in coal mining. In this paper, through theoretical analysis and numerical simulation, the pressure relief mechanism of the gob-side entry retaining by roof cutting and pressure release (RCPR) and the spatiotemporal development law of surrounding rock stress of the gob-side entry were analyzed. The studies showed that the gob-side entry retaining by RCPR shortened the length of the lateral cantilever by directional roof cutting, which weakened the stress level of the gob-side entry. In the meantime, the goaf gangues could play a good filling role by using their breaking and swelling characteristics under the action of gangue-blocking supports and further optimized the stress environment along the roadway. Field industrial tests verified that the gob-side entry retaining by RCPR had a significant effect on pressure relief, and the surrounding rock stress and deformation tended to stabilize after about 160 m of lagging working face. Numerical analysis reproduced the whole process of “mining-retention-using” of roof cutting roadway and revealed that surrounding rocks were always in the zone of relative stress reduction during the whole process. The peak value of mining-induced lateral stress was about 10 m away from the middle point of the gob-side entry. The change of surrounding rock stress could be divided into three stages: significant increase, dynamic adjustment, and stable stage. However, during the second mining, the stress connected zone would appear on the leading working face, and the stress concentration in this zone was significant. Based on the above analysis, we concluded that the new technology could be applied to the medium-thickness coal seam in the composite roof.

Coal Seam Roadway Bolt Support Design Method Based on the Supporting Theory of Broken Rock Zone

2013 ◽  
Vol 734-737 ◽  
pp. 535-539
Author(s):  
Hai Yuan Liu ◽  
Zhi Gang Wang ◽  
Ji Li ◽  
Lang Bai
Keyword(s):  
Theoretical Foundation ◽  
Design Method ◽  
Field Application ◽  
Surrounding Rock ◽  
Support Design ◽  
Roadway Support ◽  
The Stability ◽  
Comprehensive Classification ◽  
Classification Index ◽  
Surrounding Rock Deformation

broken rock zone is the main reason for the convergence of surrounding rock deformation, and its thickness not only is a reflection of many factors which influence the stability of surrounding rock, but also is the results of the interaction of many factors, a comprehensive classification index. Roadway support design based on classification result of broken rock zone, has a solid theoretical foundation, and the field application effect is remarkable.

Reinforced Techniques Analysis of Goaf-Side Entry at Isolated Island Coal Face Based on FLAC Numerical Simulation

2012 ◽  
Vol 605-607 ◽  
pp. 210-214 ◽  
Author(s):  
Wen Hua Zha
Keyword(s):  
Surrounding Rock ◽  
Good Effect ◽  
Control Problems ◽  
Rock Stress ◽  
Coal Face ◽  
The Third ◽  
Result Show ◽  
Surrounding Rock Control ◽  
Stress And Deformation ◽  
Surrounding Rock Stress

According to control problems of surrounding rock at isolated island coal face, taking isolated island coal 1251（3）face ventilation tunnel of PanSan mine as engineering background, this paper puts forward three reinforcement schemes based on the idea of turning later recovery to former reinforcement. Simulation has been done on the character of surrounding rock stress and deformation distribution and supporting structure force of three different schemes by FLAC3D. Finally optimal scheme is the third scheme. The application result show that anchor-net-cable support combined with anchor grouting support has got a good effect. The large deformation of surrounding rock is controlled efficiently and tunnel surrounding rock stable is guaranteed. The study provides a basis for goaf-side entry surrounding rock control under similar conditions.

Surrounding Rock Stress and Deformation Evolution Character Analysis of Circular Openings in Deep Underground Engineering

2011 ◽  
Vol 418-420 ◽  
pp. 2001-2005
Author(s):  
Ai Ping Yuan ◽  
Mao Wei Ji ◽  
Dai Qiang Deng
Keyword(s):  
Hard Rock ◽  
Confining Pressure ◽  
Surrounding Rock ◽  
Rock Stress ◽  
Underground Engineering ◽  
High Confining Pressure ◽  
Deep Underground ◽  
Stress And Deformation ◽  
Peak Value ◽  
Surrounding Rock Stress

Hard rock generally performs ideal plastic character after the stress reaches its peak value with high confining pressure. Once the plastic strain satisfies certain condition, the brittle failure occurs, and the rock mass located in the residual region. Based on the mechanical model of hard rock under high confining pressure, we studied the surrounding rock stress and deformation evolution law of circular openings. The results shows that there is a significant end constraint effect at the opening face, and the deformation induced by disturbance is about one sixth of its total value. The results can provide theoritical foundation for deep underground engineer lining design.

Field Monitoring of Surrounding Rock Stress and Rheological Analysis in Tunnel Construction

2011 ◽  
Vol 261-263 ◽  
pp. 1079-1083 ◽  
Author(s):  
Qiang Huang ◽  
Ying Na Dong ◽  
Zhi Da Li
Keyword(s):  
Numerical Simulation ◽  
Spatial Effect ◽  
Surrounding Rock ◽  
Monitoring Data ◽  
Rock Stress ◽  
Stress Variation ◽  
Rheological Analysis ◽  
Tunnel Diameter ◽  
Simulation Results ◽  
Surrounding Rock Stress

The stress field monitor and rheological analysis have been done during excavation. The field monitoring data are compared with numerical simulation results. The result shows: Rock stress variation is influenced by both spatial effect and time effect; when the distance from monitoring section to tunnel face is less than a tunnel diameter, the surrounding rock stress is mainly affected by spatial effect and changes violently; when the distance is more than a tunnel diameter, the surround rock presents rheological properties and stress changes smoothly and continuously. Analyzing the monitoring data and fitting by Poynting-Thomson three-parameter rheological model, we can get the radial stress variation equation with time and predict the final variation value. The final value and numerical simulation results are in comparative agreement.

The Damage Mechanics Model of the Wellbore Surrounding Rock Based on Fractal Theory

2013 ◽  
Vol 423-426 ◽  
pp. 1623-1626
Author(s):  
Rui Xiang Shi ◽  
Chi Ai ◽  
Wan Chun Zhao ◽  
Xiao Han Feng
Keyword(s):  
Calculation Method ◽  
Damage Mechanics ◽  
Fractal Theory ◽  
Fractal Model ◽  
Surrounding Rock ◽  
Distribution Model ◽  
Rock Stress ◽  
Mechanics Model ◽  
Fracture Damage ◽  
Surrounding Rock Stress

In order to describe the mechanical characteristics of CBM wellbore surrounding rock more accurately, the article establishes the CBM wellbore surrounding rock mechanics model based on the fractal theory. According to the pores of CBM surrounding rock and the characteristics of mass fractal, people find the macro fracture and micro fracture damage characteristics and build the relationship of any scale coal strength, damage variable and fractal dimension. According to the numerical calculation method of the surrounding rock stress, people find the surrounding rock stress calculation method and the damage distribution model of the pore fractal model and fracture fractal model.

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