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.

scholarly journals Numerical Simulation of Surrounding Rock Stress under Different Overlying Strata Combinations in Sijiazhuang Mine

2018 ◽  
Vol 53 ◽  
pp. 03031
Author(s):  
Jun He
Keyword(s):  
Numerical Simulation ◽  
Stress Concentration ◽  
Stress Distribution ◽  
Coal Mine ◽  
Surrounding Rock ◽  
Theoretic Model ◽  
Rock Stress ◽  
Pressure Relief ◽  
Surrounding Rock Stress ◽  
Overlying Strata

Sijiazhuang coal mine is taken as an example in this paper. Both the theoretic model and the numerical simulation are carried out to analyze the stress distribution regularity on the surrounding rock of stope face under different overlying strata combinations by using discrete element method. Under different combinations of the overlying strata, the results indicate that the regularity of stress distribution around stope face is roughly the same, i.e. the stress concentration of different degree appears in both ends, and the region of pressure relief exist above the stope face. Furthermore, destruction degree of the roof in stope face is different under various overlying strata combinations. On the eve of the first weighting, the different combinations present different phenomenon of concentration, especially the soft-hard-soft combination and hard-soft-hard combination.

scholarly journals Fracture characteristics of basic roof and mechanism of strata behavior in a pillarless working face

2021 ◽  
Vol 18 (6) ◽  
pp. 875-889
Author(s):  
Shuai Guo ◽  
Yang Tai ◽  
Zi-Wei Wang ◽  
Bo-Wen Shi ◽  
Kun Yang
Keyword(s):  
Coal Mining ◽  
Three Dimensional ◽  
Surrounding Rock ◽  
Rock Stress ◽  
Fracture Characteristics ◽  
Working Face ◽  
Strata Behavior ◽  
Hinged Plate ◽  
Basic Roof ◽  
Surrounding Rock Stress

Abstract As a research hotspot, pillarless coal mining technology has a high resource recovery rate and low roadway surrounding rock stress. To grasp the three-dimensional fracture characteristics of the basic roof is the basic to reveal the strata behavior mechanism in the pillarless working face. Thus, aiming at pillarless coal mining, the analytical solution of three-dimensional fracture mechanics models of a basic roof was analyzed by elastic thin plate theory; the principal stress distribution of a basic roof being cut by continuous artificial fractures and discontinuous artificial fractures was analyzed; the fracture characteristics of the basic roof was revealed and the strata behavior mechanism was obtained. The following conclusions can be drawn: (i) an ‘O + X’ fracture occurred in the basic roof of a traditional working face, while an opposite-trapezoid-shaped or ≡-shaped fracture was generated in the pillarless working face. (ii) When the basic roof broke, the trapezoidal or rectangular hinged plate traversed the entire pillarless working face, causing the end supports to be pressured, while the trapezoidal hinged plate did not traverse the entire traditional working face and the end supports were not pressured. (iii) The break of a basic roof induced by artificial fractures in pillarless mining reduced or even eliminated the triangular hinged plate area along the goaf edges, making a roadway in the stress relief zone. (iv) Compared with the fractures in traditional roadways and in a discontinuous roof-cutting roadway, continuous fractures could minimize surrounding rock stress and make it easy to maintain a roof-cutting roadway.

scholarly journals Pressure-Relief Mechanism and Application of Large-Diameter Boreholes in Coal Seams with Rockburst Hazard

Geofluids ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-9
Author(s):  
Zhen Hao ◽  
Guangzhong Sun ◽  
Haihang Wei ◽  
Jiayu Liu ◽  
Maolin Tian ◽  
...  
Keyword(s):  
Stress Concentration ◽  
Plastic Zone ◽  
Coal Seam ◽  
Large Diameter ◽  
Engineering Application ◽  
Surrounding Rock ◽  
Pressure Relief ◽  
Effective Measure ◽  
Rockburst Hazard ◽  
Working Face

Drilling of large-diameter boreholes is regarded as an effective measure for rockburst prevention. By investigating the morphological characteristic and evolution of plastic zone in borehole surrounding rock, the pressure-relief mechanism of large-diameter borehole was ascertained, and the engineering application of large-diameter boreholes was assessed in the 13230 working face of Gengcun Coal Mine, Henan Province, China. The results showed that (1) the plastic zone in surrounding rock of borehole appear as circular, elliptical, and butterfly shapes, in which the maximum size of the butterfly wings of the plastic zone is several times larger than the borehole diameter; (2) under certain stress conditions, multiple large-diameter boreholes distributed in coal seam with rockburst risk lead to the generation and coalescence of large-range butterfly-shape plastic zone. They reduce the stress concentration and capacity for storing elastic energy of coal seam, thus reducing the rockburst risk of the coal seam; (3) large-diameter boreholes significantly decrease the stress concentration in front of the 13230 working face and improve the stress environment in the head entry, promoting the safe mining of the working face.

Study on the Mining Induced Stress of Hard Surrounding Rock under Dynamic Pressure

2014 ◽  
Vol 941-944 ◽  
pp. 2565-2569
Author(s):  
Ji Ping Liu ◽  
Shao Jian Zhan ◽  
Yun Peng Guan ◽  
Li Jing Chuan ◽  
Jun Tang ◽  
...  
Keyword(s):  
Theoretical Analysis ◽  
Dynamic Pressure ◽  
Field Monitoring ◽  
Surrounding Rock ◽  
Rock Stress ◽  
Large Area ◽  
Pressure Behavior ◽  
Induced Stress ◽  
Working Face ◽  
Surrounding Rock Stress

There is a series of features of the strata-pressure behavior of hard surrounding rock which is affected by dynamic pressure, such as the caving of the roof is difficult, sudden and large-area. In this paper we focus on the mining and support of 14-1103 working face, In view of the problems of the mine such as the roof is hard to caving, the suspension-area is huge and the safe of the working face is under a great threat, theoretical analysis and field monitoring is used in the study of the strata-pressure behavior. The study indicates that the influence of the advance on the surrounding rock stress is in the range of 100m, the scope in which the surrounding rock stress is remarkably affected is 20~30m; the stress of the surrounding rock is more affected in the scope of fault; the growing time of the roof stress is 2~3 days and is much shorter than the time of roadway’s sides which is 5~9 days.

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 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.

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.

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.

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