scholarly journals Study on Stability Control of Retained Gob-Side Entry by Blasting Fracturing Roof Technology in Thick Immediate Roof

2021 ◽  
Vol 2021 ◽  
pp. 1-12
Author(s):  
Jingang Guo ◽  
Yaohui Li ◽  
Fulian He ◽  
GuangSheng Fu ◽  
Sheng Gao
Keyword(s):  
Longwall Mining ◽  
Stability Control ◽  
Surrounding Rock ◽  
Field Practice ◽  
Immediate Roof ◽  
Stress Environment ◽  
The Stability ◽  
Mining Coal ◽  
Stress Damage ◽  
Double Yield

A retained gob-side entry technique is popular in longwall mining coal mines, because the excavation of an entry is reduced for the next panel. However, it is influenced by multiple excavations and mining, so the stability control of the surrounding rock becomes a problem. In view of the above problems, a typical retained gob-side entry with thick immediate roof was carried out, and a blasting fracturing roof technology was used in it to improve the stress environment, reduce the deformation and damage, and ensure stability and safety. To study the fracturing roof parameters, a global model with thick immediate roof considering strain-soft and double-yield constitution was built. It found that the stress, damage range, and deformation of surrounding rock were closely related to the height and angle of fracturing roof, and an optimal case was given out. The simulation result was applied to the field practice, and a good application effect was achieved. The above technique and research method can be used as a reference for the coal mine with similar conditions.

scholarly journals Stability of "Support-Surrounding Rock" System for Fully Mechanized Longwall Mining in Steeply Dipping Coal Seams

2021 ◽  
Author(s):  
Luo Shenghu ◽  
tong wang ◽  
Wu Yongping ◽  
Huangfu Jingyu ◽  
Zhao Huatao
Keyword(s):  
Coal Seam ◽  
Longwall Mining ◽  
Stability Control ◽  
Surrounding Rock ◽  
Coal Seams ◽  
Physical Test ◽  
Rock System ◽  
Working Face ◽  
The Stability ◽  
Mining Height

Abstract The key to the safe and efficient longwall mining of steeply dipping seams lies in the stability control of the "support-surrounding rock" system. This paper analyzes the difficulty of controlling the stability of the support during the longwall mining process of steeply dipping coal seams in terms of the characteristics of the non-uniform filled-in gob using a combination of physical test, theoretical analysis and field measurements. Considering the floor as an elastic foundation, we built a "support-surrounding rock" mechanical model based on data obtained on "support-surrounding rock" systems in different regions and the laws of support motion under different load conditions. Our findings are summarized as follows. First, depending on the angle of the coal seam, the caving gangue will roll (slide) downward along the incline, resulting in the formation of a non-uniform filling zone in the deep gob in which the lower, middle, and upper sections are filled, half-filled, and empty, respectively. In addition, an inverted triangular hollow surface is formed on the floor of the gob in the middle and upper sections behind the support. Furthermore, as the angle of the coal seam, length of the working face, and mining height increase, the characteristics of the non-uniform filled-in gob are enhanced. Second, we found that, as a result of support by the gangue, the "support-surrounding rock" system is relatively stable in the lower part of the working face while, in the middle and upper sections of the working face, the contact method and loading characteristics of the support are more complicated, making stability control difficult. Third, the magnitude and direction of the load, action point, and mining height all affect the stability of the support to varying degrees, with the tangential load and action position of the roof load having the most significant impacts on the stability of the support. Under loading by the roof, rotation and subsidence of the support inevitably occur, with gradually increasing amplitude and effects on the inter-support and sliding forces. Finally, we found that it is advisable in the process of moving the support to adopt "sliding advance of support" measures and to apply a "down-up" removal order to ensure overall stability. These research results provide reference and guidance of significance to field practice production.

scholarly journals Study of the Stability Control of the Rock Surrounding Double-Key Strata Recovery Roadways in Shallow Seams

2019 ◽  
Vol 2019 ◽  
pp. 1-21 ◽  
Author(s):  
Cheng Zhu ◽  
Yong Yuan ◽  
Zhongshun Chen ◽  
Zhiheng Liu ◽  
Chaofeng Yuan
Keyword(s):  
Engineering Application ◽  
Stability Control ◽  
Surrounding Rock ◽  
Control Effect ◽  
Pressure Relief ◽  
Support Design ◽  
Key Strata ◽  
Fracture Development ◽  
Surrounding Rock Control ◽  
The Stability

The stability control of the rock surrounding recovery roadways guarantees the safety of the extraction of equipment. Roof falling and support crushing are prone to occur in double-key strata (DKS) faces in shallow seams during the extraction of equipment. Therefore, this paper focuses on the stability control of the rock surrounding DKS recovery roadways by combining field observations, theoretical analysis, and numerical simulations. First, pressure relief technology, which can effectively release the accumulated rock pressure in the roof, is introduced according to the periodic weighting characteristics of DKS roofs. A reasonable application scope and the applicable conditions for pressure relief technology are given. Considering the influence of the eroded area on the roof structure, two roof mechanics models of DKS are established. The calculation results show that the yield load of the support in the eroded area is low. A scheme for strengthening the support with individual hydraulic props is proposed, and then, the support design of the recovery roadway is improved based on the time effects of fracture development. The width of the recovery roadway and supporting parameters is redesigned according to engineering experience. Finally, constitutive models of the support and compacted rock mass in the gob are developed with FLAC3D software to simulate the failure characteristics of the surrounding rock during pressure relief and equipment extraction. The surrounding rock control effects of two support designs and three extraction schemes are comprehensively evaluated. The results show that the surrounding rock control effect of Scheme 1, which combines improved support design and the bidirectional extraction of equipment, is the best. Engineering application results show that Scheme 1 realizes the safe extraction of equipment. The research results can provide a reference and experience for use in the stability control of rock surrounding recovery roadways in shallow seams.

scholarly journals Stability Analysis of Surrounding Rock of Large Section Ultradeep Shaft Wall

2021 ◽  
Vol 2021 ◽  
pp. 1-10
Author(s):  
Cheng Li ◽  
Wang Chunlong ◽  
Wang Xi ◽  
Chen Kexu
Keyword(s):  
Control Method ◽  
Stress Test ◽  
Stability Control ◽  
Surrounding Rock ◽  
Main Shaft ◽  
Large Section ◽  
Masonry Construction ◽  
Temporary Support ◽  
The Stability ◽  
Shaft Wall

In order to study the stability of deep surrounding rock during the excavation of new main shaft in Xincheng gold mine, a construction method suitable for large section ultradeep shaft is proposed. A series of analyses were carried out in this study, including the in situ stress test, stress response of surrounding rock disturbance, deformation and failure characteristics, and numerical simulation. Based on the above analysis, the stability control method of surrounding rock in the process of deep excavation of the new main shaft is proposed. The results show that (1) the maximum principal stress of deep surrounding rock of new main shaft is horizontal stress, and the surrounding rock of the shaft has strong rock burst tendency after excavation; (2) the influence range of the deep shaft excavation disturbance is 6.4 times the shaft radius, in which the temporary support should be strengthened to avoid the influence of excavation disturbance on the stability of shaft wall rock; (3) the failure shape of surrounding rock of the deep shaft excavation was “ear” failure, and the failure depth was not more than 2.5 m; (4) after replacing the original “one-excavation and one-masonry” construction with “three-excavation and one-masonry” construction, the temporary support span of the main shaft was adjusted to 12 m, which can make the subsequent concrete shaft wall in the state of “no pressure bearing or slow low pressure bearing,” and the lining compressive safety coefficient was increased to 1.98, which meets the safety requirements.

The Stability Control Technology of Crosscut while Mining without Coal Pillar in Steep Seam

2011 ◽  
Vol 90-93 ◽  
pp. 2073-2079
Author(s):  
Yu Feng Wang ◽  
Zhi Qiang Liu ◽  
Bin Song Jiang
Keyword(s):  
Support System ◽  
Coal Pillar ◽  
Stability Control ◽  
Surrounding Rock ◽  
Steep Seam ◽  
Floor Rock ◽  
Long Term Stability ◽  
Rock Collapse ◽  
The Stability

In order to improve the mining benefit of coal resources, Chang Gouyu Coal Mine carried out the technology of mining without coal pillar in steep seam. The key of the technology was to ensure a long-term stability of the cross-entry roadway across the seam. Through the analysis of the nature of steep seam roof and floor rock, and based on the stability analysis and loose circle measured of surrounding rock of crosscut roadway, we brought forward adopting shotcrete rockbolt mesh and U-shaped steel complex support structure system. This complex support system could flex lengthways and compress in radial direction. The entirety integrated with the surrounding rock, and they formed into a whole. Application of the complex support system could effectively control the deformation of the surrounding rock collapse, and maintain the stability of the crosscut.

scholarly journals The segmental subsidence structure with immediate roof of gob side entry retaining in backfill mining

2021 ◽  
pp. 014459872199654
Author(s):  
Xin-yuan Zhao ◽  
Xin-wang Li ◽  
Ke Yang ◽  
Zhen Wei ◽  
Qiang Fu
Keyword(s):  
Mechanical Model ◽  
Surrounding Rock ◽  
Extreme Conditions ◽  
Structure Characteristics ◽  
Rock Structure ◽  
Immediate Roof ◽  
Backfill Mining ◽  
The Difference ◽  
The Stability ◽  
Supporting Force

When gob side entry retaining is carried out in backfill mining, the roof will show different subsidence morphology due to the difference of compactness and supporting force of the backfill body at different positions. This paper analyzed the immediate roof subsidence structure under two extreme conditions, constructed the roof segmented subsidence structure and the mechanical model of roadside backfill body, and used FLAC3D software to investigate the roof migration and the force law of the roadside backfill body under the conditions of different goaf backfilled rates, different width and strength of roadside backfill body. Finally, the backfill practice of a mine in Shandong Province of China is taken as an example for analysis. The results show that the segmented subsidence structure of the immediate roof is related to the mechanical properties of the roadside backfill body and the goaf backfill body. When the backfilled rate of goaf decreases from 95% to 70%, the width of roadside backfill body decreases from 5 m to 1 m, and the elastic modulus decreases from 10 GPa to 0.5 GPa, the greater difference in the subsidence and inclination of the immediate roof on both sides of the roadside backfill body is, the more obvious the segmented subsidence structure characteristics of the immediate roof are, and the greater force on the roadside backfill body will be, the more unfavorable it is to maintain the stability of the roadway surrounding rock and the roadway backfill body. Therefore, when gob side entry retaining is carried out in backfill mining, the surrounding rock structure and the force on roadside backfill body should be considered comprehensively.

scholarly journals A Case Study on Optimization and Control Techniques for Entry Stability in Non-Pillar Longwall Mining

Energies ◽  
2019 ◽  
Vol 12 (3) ◽  
pp. 391 ◽  
Author(s):  
Xiaojie Yang ◽  
Eryu Wang ◽  
Xingen Ma ◽  
Guofeng Zhang ◽  
Ruifeng Huang ◽  
...  
Keyword(s):  
Large Deformation ◽  
Longwall Mining ◽  
Surrounding Rock ◽  
Control Techniques ◽  
Immediate Roof ◽  
Optimization And Control ◽  
Pillar Mining ◽  
And Control ◽  
Entry Roof

In order to reduce large deformation failure occurrences in non-pillar longwall mining entries due to roof weighting behaviors, a case study in Halagou coal mine was conducted on optimization and control techniques for entry stability in non-pillar longwall mining. The Universal Discrete Element Code (UDEC) modeling was adopted to study entry stability in non-pillar mining, and the characteristics of deformation and stress and crack propagation were revealed. The large deformation transmission between the entry-immediate roof and the gob-immediate roof could be eliminated by optimizing the entry roof structure through a directional roof-cutting method. The localized tensile stresses generated in the entry-surrounding rock caused the generation of coalescent macroscopic fractures, which resulted in the instability of the entry. The tensile stress state could be inhibited by an active flexible support system through enhancing the confining pressure on the surrounding rock. Serious rotation subsidence occurs in the entry roof due to periodic weighting of the main roof, which could be greatly reduced by a passive rigid support pattern. The numerical and field test results both showed that the roof weighting pressure was offloaded by the technique and that the deformation of the entry surrounding the rock in non-pillar mining was quite small. Thus, the technique can effectively ensure the stability of the gob-side entry, which can provide references for entry stability control in non-pillar longwall mining.

Monitoring and Reinforcement Technology of Passing Weak and Broken Rock Strata for Tunnel Boring Machine

2012 ◽  
Vol 204-208 ◽  
pp. 2819-2823
Author(s):  
Tao Li ◽  
Kai Bin Liu ◽  
Wei Hong Yang ◽  
Bo Liu ◽  
Ying Chao Liu
Keyword(s):  
Tunnel Boring Machine ◽  
Stability Control ◽  
Surrounding Rock ◽  
Tunnel Boring ◽  
Rock Stability ◽  
Tunnel Convergence ◽  
Geological Conditions ◽  
The Stability ◽  
Large Tunnel ◽  
Rock Strata

The stability control of surrounding rock is a relatively important problem in tunnel boring machine (TBM) construction. The tunnel convergence deformation value was monitored in field while TBM passing weak and broken section of hydraulic tunnel. The correlation between tunnel convergence and surrounding rock stability is analyzed. The monitoring results show that: the characteristic of weak and broken Strata is closely correlated with some geological conditions, such as fault development, intrusive contact of orthophyre and lamprophyre veins. These supporting measures can well ensure the stability of surrounding rock in weak and broken section, such as sealing the inverted arch by using concrete of C25,reinforcing the inverted arch by steel arch of I10 and anchor construction in the roof. There is great difference between the properties of the weak and broken rocks on both sides, which is the main reason of the large tunnel convergence deformation. The monitoring results can provide reference for similar engineering in the future.

scholarly journals Research on the Transmission of Stresses by Roof Cutting near Gob Rocks

Energies ◽  
2021 ◽  
Vol 14 (5) ◽  
pp. 1237
Author(s):  
Zhibiao Guo ◽  
Haohao Wang ◽  
Zimin Ma ◽  
Pengfei Wang ◽  
Xiaohui Kuai ◽  
...  
Keyword(s):  
Early Stage ◽  
Pressure Coefficient ◽  
Influence Factors ◽  
Stress Transfer ◽  
Main Roof ◽  
Surrounding Rock ◽  
Pressure Relief ◽  
Rock Structure ◽  
Immediate Roof ◽  
The Stability

Pressure relief for roadways retained by roof cutting is essentially caused by stress transfer. In this paper, the stress transfer mechanism of 16011 tail entry with roof cutting in Zhaogu No.1 coal mine is studied from the following two aspects: the change of the tail entry surrounding the rock structure and the interaction between the roadway surrounding rock and supporting structures. It is found by numerical simulation that roof cutting can significantly reduce the magnitude of roadway roof stress, transferring the concentrated stress induced by excavation and mining away from the roadway, and forming an obvious triangle pressure relief area in front of the working face. In the early stage after mining, most of the overburden load is transferred downward through the immediate roof of the roadway. With the movement of overlying strata, the stress, initially transferred to the immediate roof strata, is gradually transferred to the gob, and the calculation formula and influence factors of the transferred stress are derived. In addition, through the establishment of the mechanical model and theoretical calculation of the key rock block of the main roof, the roadside support resistance required to ensure the stability of the main roof block is determined. The field monitoring shows that the lateral pressure coefficient of the roadside caved rocks is 0.36 and the constant resistance and large deformation anchor cable (CRLDAC) and the roadway temporary support play roles of conduction and control in the process of stress transfer, and effectively ensure the stability of surrounding rock during the service life of the retained gob-side entry by roof cutting (RGERC).

Stability Analysis of Tunnel during the Excavation Based on ANSYS

2014 ◽  
Vol 577 ◽  
pp. 1135-1138
Author(s):  
Bing He ◽  
Guang Zhi Yin
Keyword(s):  
Numerical Simulation ◽  
Stability Analysis ◽  
Stress Condition ◽  
Stability Control ◽  
Simulation Software ◽  
Surrounding Rock ◽  
Geological Condition ◽  
Rock Stability ◽  
Before And After ◽  
The Stability

This paper combines the geological condition of Miaoziwan tunnel and numerical simulation software ANSYS to analyze the displacement and stress condition of surrounding rock before and after the excavation. Furthermore, the stability of overlying rock in the tunnel was studied based on the displacement and stress condition of surrounding rock. The breaking law of overlying rock was studied considering the influencing factors to the stability of surrounding. The study and analysis to the breaking law of overlying rock can be helpful to the improvement of surrounding rock stability control and supporting system. Moreover, the result can be the guidance to the excavation.

scholarly journals Stability Control for Gob-Side Entry Retaining with Supercritical Retained Entry Width in Thick Coal Seam Longwall Mining

Energies ◽  
2019 ◽  
Vol 12 (7) ◽  
pp. 1375 ◽  
Author(s):  
Zizheng Zhang ◽  
Xianyang Yu ◽  
Hai Wu ◽  
Min Deng
Keyword(s):  
Longwall Mining ◽  
High Water ◽  
Stability Control ◽  
Surrounding Rock ◽  
Cusp Catastrophe ◽  
Construction Technology ◽  
Thick Coal Seam ◽  
Filling Materials ◽  
Rock Stability ◽  
Set Up

Taking gob-side entry retaining with large mining height (GER-LMH) of the 4211 panel in the Liujiazhuang coal mine as the engineering background, a numerical simulation was conducted to study the surrounding rock deformation, stress, and plastic zone distribution of GER-LMH with respect to retained entry width. The concept of critical retained entry width of GER-LMH was proposed. In view of the deformation characteristics of surrounding rock, an innovative approach to determine the critical width of GER-LMH based on the cusp catastrophe theory was proposed. The cusp catastrophe functions were set up by approximate roadside backfill body rib convergence and roof subsidence series with respect to different retained entry widths. The critical retained entry width of GER-LMH was 4.0 m according to bifurcation set equations. Surrounding rock stability control principle and technique of GER-LMH was proposed, including “rib strengthening and roof control”: road-in support with high pre-stress rockbolts and anchor cables, roadside backfill body construction technology with high-water quick consolidated filling materials and counter-pulled rockbolt, road-in reinforced support technology with hydraulic prop support and roof master. Field test and field monitoring results show that GER-LMH with supercritical retained entry width in the 4211 panel could meet the requirements for ventilation when the 4211 panel was retreating.

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