scholarly journals Novel Application of the Roof-Cutting-Type Gob-Side Entry Retaining in Coal Mine

2021 ◽  
Vol 2021 ◽  
pp. 1-16
Author(s):  
Jiong Wang ◽  
Wenfei Li ◽  
Daoyong Zhu ◽  
Weili Gong ◽  
Yi Su
Keyword(s):  
Stable State ◽  
Stress Evolution ◽  
Coal Seams ◽  
Working Face ◽  
Mining Conditions ◽  
Support Resistance ◽  
Stress And Deformation ◽  
Cutting Height ◽  
Roof Deformation ◽  
Overlying Strata

In this study, the roof-cutting-type gob-side entry retaining is introduced, and its application in medium-thickness coal seams is studied. Based on the analysis of the construction procedure and principle, the mechanical model of the retained roadway structure and cantilever beam formed by roof cutting was established, and the support resistance and roof deformation were obtained. In addition, through technological design analysis and numerical simulation, the parameters of roof cutting were determined. The roof-cutting height and angle were designed to be 9 m and 15°, respectively. Flac3 D was used to analyze the stress evolution law under different mining conditions. The stress on the integrated coal side and roof subsidence was lower when the roof-cutting height was 8∼10 m and the cutting angle was 15°. Through field monitoring, the roof pressure, gob-side lateral gangue retaining pressure, anchor cable stress, and deformation of the surrounding rock eventually reached a stable state. This indicates that the roof cutting can effectively cut down the overlying strata over the gob and form a stable entry structure to meet the requirements of the next working face.

scholarly journals Study and Application of Roof Cutting Pressure Releasing Technology in Retracement Channel Roof of Halagou 12201 Working Face

2018 ◽  
Vol 2018 ◽  
pp. 1-15 ◽  
Author(s):  
Ma Xingen ◽  
He Manchao ◽  
Wang Yajun ◽  
Zhang Yong ◽  
Zhang Jiabin ◽  
...  
Keyword(s):  
High Stress ◽  
Hydraulic Support ◽  
Working Face ◽  
Geological Conditions ◽  
Support Resistance ◽  
Cutting Effect ◽  
Mining Pressure ◽  
Cutting Height ◽  
First Time ◽  
Roof Deformation

The retracement channel roof cutting (RCRC) technology can change the overburden structure actively by cutting off the roof of channel along the direction of working face tendency and make use of the gangue collapsing from roof cutting range to fill the goaf and weaken the mining pressure during the retracement process of working face. In order to solve the problems of high stress in surrounding rock and serious deformation of retracement channel in Halagou coal mine, it is the first time that the pressure releasing test is carried out on the 12201 working face by the method of the directional presplitting roof cutting in retracement channel. First, according to statics theory and energy theory, the stress state of hydraulic support and roof deformation mechanism of retracement channel are analyzed. Then the roof cutting design of retracement channel is determined according to the geological conditions of 12201 working face, and the cutting effect is analyzed by numerical simulation. Finally, the field test is carried out on the 12201 working face to verify the effect of pressure releasing by roof cutting. The result shows that, with the roof cutting design including the roof cutting height being 8m and roof cutting angle being 45°, the roof subsidence of the 12201 working face retracement channel in Halagou mine is reduced to 132.5mm, and the hydraulic support resistance is maintained at 1361KN. And there is no hydraulic support crushed; the deformation of the retracement channel is also small; namely, the effect of roof cutting for pressure releasing is obvious.

DYNA Numerical Experiment on Long-Term Stability of Strip Pillar in Deep Mine

2011 ◽  
Vol 217-218 ◽  
pp. 1520-1524
Author(s):  
Chun Qiu Wang ◽  
Shi Bin Gu ◽  
Zhong Ju Wei ◽  
Bo Li ◽  
Shao Jie Chen
Keyword(s):  
Stable State ◽  
Support Effect ◽  
Test Results ◽  
Deep Mine ◽  
Long Term Stability ◽  
Creep Stress ◽  
Working Face ◽  
Stress And Deformation ◽  
Overlying Strata

The creep test of the No. 3 coal seam of Daizhuang Coal Mine is carried. Based on the experiment results, the creep support effect of deep pillar is analyzed with LS-DYNA. The results show that the circumferential initial creep stress of the tested coal is 3.061MPa and the circumferential initial creep stress is far below the axial initial creep stress which is 7.020MPa. In addition, the creep strength is 9.3266MPa and the creep coefficient is 0.6472. According to the test results, the creep support effect of deep strip pillar can be simulated excellently with LS-DYNA. Stress and deformation in simulated strip pillar show evident rheology. Many changes will take place in the stable situation of pillar after the working face mining. Under the effect of the overlying strata, this pillar turns into steady creep state after 15~16 months, then the pillar is able to maintain long-term stable state.

scholarly journals Study on Surrounding Rock Structure Evolution Characteristics and Roof Control Techniques of the Retained Roadway Formed by Roof Cutting in Inclined Coal Seams

2021 ◽  
Vol 2021 ◽  
pp. 1-20
Author(s):  
Guangyuan Yu ◽  
Jiong Wang ◽  
Jianjun Ren ◽  
Jinzhu Hu ◽  
Zhifu Pan ◽  
...  
Keyword(s):  
Structure Evolution ◽  
Coal Seams ◽  
Supporting System ◽  
Working Face ◽  
Evolution Characteristics ◽  
Rock Structure ◽  
Support Resistance ◽  
Pillar Mining ◽  
Three Stages ◽  
Constant Support

To control the roof during gob-side entry retaining by roof cutting in inclined coal seams, the retained gob-side roadway is zoned based on the mechanical principle and technological process of no-pillar mining with gob-entry retention. A simplified mechanical model for surrounding rocks in different subzones was established by using theoretical analysis and numerical simulation to attain the demand for the support resistance and deformation of the roof in different subzones. According to load and deformation characteristics of the roof and mechanical characteristics of NPR cables, single props, and a sliding-type gangue-retaining structure formed by U-shaped steel inserts, the supporting systems for roadways in different subzones and the constitutive model thereof were established. On this basis, the action of the supporting system was analysed and a field test was performed. The results show that the supporting system undergoes three stages of behaviour, i.e., pressure growth, yielding under constant pressure, and stabilisation during whole entry retention. It can guarantee the collaborative deformation of the supporting systems with the roof on the premise of constant support resistance, thus satisfying the requirement for roadway protection. The roadway 150 m back from the working face is stable, and the final convergence between the roof and floor of the retained entry is 257 mm, showing a favourable entry-retention effect.

scholarly journals Analysis of Roof Deformation Mechanism and Control Measures with Roof Cutting and Pressure Releasing in Gob-Side Entry Retaining

2021 ◽  
Vol 2021 ◽  
pp. 1-13
Author(s):  
Bing-Jun Sun ◽  
Xin-Zhu Hua ◽  
Yan Zhang ◽  
Jiadi Yin ◽  
Kai He ◽  
...  
Keyword(s):  
Numerical Simulation ◽  
Coal Mine ◽  
Surrounding Rock ◽  
Cutting Angle ◽  
Working Face ◽  
Support Resistance ◽  
Key Block ◽  
Cutting Height ◽  
Basic Roof ◽  
Roof Support

The mechanical model of the basic roof fracture structure is established on the basis of key block theory to study the roof breaking mechanism of gob-side entry retaining under roof cutting and pressure relief, and the analytical formula of roof support resistance is derived when the key block of the basic roof is stable. The influence of roof cutting angle and cutting height on roof support resistance is also analyzed. Determining the cutting seam parameters of the retained roadway roof is necessary to identify the support resistance of the roadway roof due to the correlation between the roof cutting parameters and the support resistance. Taking the II 632 haulage drift of the Hengyuan coal mine as the engineering background, FLAC3D numerical simulation is used in this paper to analyze the influence of different roof cutting angles and cutting heights on the surrounding rock structure evolution of retained roadways. Results show that the roof cutting angle and cutting height respond to the support resistance of the retained roadway roof, and the support resistance required by the roof increases with the roof cutting angle and cutting height. This condition ensures that the side roof of the gob can be cut off smoothly, and the support resistance required by the roof of retained roadways is within a reasonable range. Through theoretical and numerical simulation analysis, the reasonable roof cutting height of II 632 haulage drift is 8 m and the roof cutting angle is 15°. The theoretical analysis and numerical simulation results reveal that the required support resistance to maintain the stability of the roadway roof is 0.38 MPa. The supporting scheme of the roof of the II 632 haulage drift in the Hengyuan coal mine is then designed. Finally, the field industrial test is used for verification. The borehole imaging results show that the overall line of the retained roadway roof is small based on the description of field monitoring results. The deformation of the surrounding rock surface of the retained roadway is less than 100 mm, and the roadway is 40 m from the lagging working face. The deformation rate of surrounding rock decreases with the increase in distance from the working face. The integrity of the retained roadway roof is good, and the deformation of the surrounding rock is effectively controlled.

scholarly journals Research on the Deformation Mechanism and Directional Blasting Roof Cutting Control Measures of a Deep Buried High-Stress Roadway

2020 ◽  
Vol 2020 ◽  
pp. 1-14
Author(s):  
Xiaojie Yang ◽  
Chenkang Liu ◽  
Honglei Sun ◽  
Songlin Yue ◽  
Yuguo Ji ◽  
...  
Keyword(s):  
Numerical Simulation ◽  
High Stress ◽  
Stable State ◽  
Surrounding Rock ◽  
Pressure Relief ◽  
Working Face ◽  
Rock Structure ◽  
Stress Fluctuation ◽  
Roadway Deformation ◽  
Cutting Height

Affected by the mining activities of the working face, the surrounding rock of the roadway is easily deformed and destroyed. For deep buried roadways, the deformation and destruction of the surrounding rock is particularly prominent. Under the influence of in situ stress fluctuation, 3−1103 tailgate of the Hongqinghe coal mine was in a complex stress environment with a maximum stress exceeding 20 MPa. Affected by mining stress, the roadway behind the working face was seriously deformed. In order to alleviate the deformation of the roadway, directional blasting and cutting measures for the 3−1103 tailgate were adopted in this paper. The mechanism of crack propagation in single-row to three-hole directional blasting was revealed by numerical simulation. The blasted rock was divided into three regions according to the crack condition. The numerical analysis of the cutting heights of 0 m, 10 m, 12 m, and 14 m, respectively, showed the stress peaks of different cutting heights and the deformation law of the surrounding rock. The pressure relief effect was the best at 14 m cutting height. At this time, the peak stress was 39 MPa with the smallest roadway deformation. Based on numerical simulation and theoretical analysis results, engineering tests were carried out. Field monitoring showed that the deformation of the roadway was inversely proportional to the roof cutting height. The higher the cutting height is, the more preferential the roadway is to reach the stable state. It can be concluded that directional blasting can change the surrounding rock structure, control the deformation of the roadway, and play a role in pressure relief. It provides a new measure to control roadway deformation.

Analysis on Key Strata’s Subsidence in Paste-Like Filling Face

2012 ◽  
Vol 524-527 ◽  
pp. 525-530
Author(s):  
Jian Hao ◽  
Yong Kui Shi ◽  
Kuan Liu
Keyword(s):  
Lower Layer ◽  
Early Stage ◽  
Stable State ◽  
Key Strata ◽  
Primary Stress ◽  
Ground Pressure ◽  
Working Face ◽  
High Layer ◽  
Supporting Force ◽  
Overlying Strata

Using theoretical analysis and actually test research to analyze stress condition of filling body and average subsidence of the key strata, analysis shows that the average vertical stress in filling body was about 15Mpa when entering into stable state, which is equal to the primary stress, 13.75Mpa. The filling body could tighten the roof well and the filling body can support full weight of the overlying strata. The limestone, thickness of 5.3m, above the 81006 working face is the key strata of mining stope. On the interaction between ground pressure and the supporting force of filling body, the whole key strata subsided about 98.64mm on average theoretically, as the height meter monitored, the subsidence value of key strata was 108mm on average, conforms to the theoretical value, which proves the filling effect was good. At the early stage after filling, the roof subsided relatively faster as the filling body had not coagulated completely and the strength was lower. At this stage the roof was not tightened enough with the filling body, it subsided relatively faster in some certain limited space. After a while, the limestone, the key strata of mining stope, became stable for a short term, and then it would continue to subside until being stable under the disturbance of the high layer, because the movement of lower layer created some space for high layer.

scholarly journals Study on strata behavior law of deep inclined coal seam

2021 ◽  
Vol 248 ◽  
pp. 03031
Author(s):  
Chen Zhengwen
Keyword(s):  
Numerical Simulation ◽  
Stress Distribution ◽  
Surrounding Rock ◽  
Rock Deformation ◽  
Coal Seams ◽  
Working Face ◽  
Support Resistance ◽  
Strata Behavior ◽  
The Law ◽  
Surrounding Rock Deformation

In order to understand and grasp the law of roof pressure on the working face of deep inclined coal seams, the law of support resistance distribution, the law of leading support stress distribution and the law of surrounding rock deformation of the two roadways, the 94101 working face of Zhangshuanglou Coal Mine was taken as the engineering background. Through a combination of field measurement, numerical simulation, theoretical analysis, etc, this paper analyzes the laws of roof migration and rock pressure manifestation in deep inclined coal seams.

scholarly journals Roof Cutting Parameters Design for Gob-Side Entry in Deep Coal Mine: A Case Study

Energies ◽  
2019 ◽  
Vol 12 (10) ◽  
pp. 2032 ◽  
Author(s):  
Deyuan Fan ◽  
Xuesheng Liu ◽  
Yunliang Tan ◽  
Shilin Song ◽  
Qingheng Gu ◽  
...  
Keyword(s):  
Numerical Simulation ◽  
Coal Mine ◽  
Cutting Parameters ◽  
Surrounding Rock ◽  
Vertical Stress ◽  
Deep Mining ◽  
Cutting Angle ◽  
Working Face ◽  
Mining Conditions ◽  
Cutting Height

Roof cutting is an effective technique for controlling the deformation and failure of the surrounding rock in deep gob-side entry. The determination of the roof cutting parameters has become a popular research subject. Initially, two mechanical models are established for the non-roof-cutting and roof-cutting of gob-side entry in deep mining conditions. On this basis, the necessity and significance of roof cutting is revealed by analysing the stress and displacement of roadside prop. The Universal Distinct Element Code numerical simulation model is established to determine the key roof-cutting parameters (cutting angle and cutting height) according to the on-site situation of No. 2415 headentry of the Suncun coal mine, China. The numerical simulation results show that with the cutting angle and height increase, the vertical stress and horizontal displacement of the coal wall first increase and then decrease, as in the case of the vertical stress and displacement of roadside prop. Therefore, the optimum roof cutting parameters are determined as a cutting angle of 70° and cutting height of 8 m. Finally, a field application was performed at the No. 2415 headentry of the Suncun coal mine. In situ investigations show that after 10 m lagged the working face, the stress and displacement of roadside prop are obviously reduced with the hanging roof smoothly cut down, and they are stable at 19 MPa and 145 mm at 32 m behind the working face, respectively. This indicates that the stability of the surrounding rock was effectively controlled. This research demonstrates that the key parameters determined through a numerical simulation satisfactorily meet the production requirements and provide a reference for ensuring safe production in deep mining conditions.

scholarly journals Study on Law of Overlying Strata Breakage and Migration in Downward Mining of Extremely Close Coal Seams by Physical Similarity Simulation

2020 ◽  
Vol 2020 ◽  
pp. 1-11
Author(s):  
Xiaobin Li ◽  
Wenrui He ◽  
Zhuhe Xu
Keyword(s):  
Coal Seam ◽  
Coal Pillar ◽  
Coal Seams ◽  
Monitoring Point ◽  
Rock Stratum ◽  
Working Face ◽  
Roof Fall ◽  
And Migration ◽  
Close Coal Seams ◽  
Overlying Strata

Extremely close coal seam groups are widely distributed in China, and the main mining method is downward mining. In the downward mining process of extremely close coal seam groups, the violent movement of overlying strata will cause the redistribution of surrounding rock stress. It not only produces stress concentration on the pillar but also causes the roof of the lower coal seam to be broken and difficulty in maintaining the mining roadway. In this study, the physical similitude modeling method and field observations were used to study the breakage and migration law of overlying strata in the downward mining of extremely close coal seams. Results show that in the process of mining upper coal seam, the first weighting step of the main roof is 37.5 m and the periodic weighting step is 12.5 m. The occurrence of strata separation is beneficial to the prediction of roof weighting. When the working face advances to 25 m, the rock stratum approximating a parallelogram of height 5 m does not collapse, and the working face is relatively dangerous. When mining the lower coal seam, the overall pressure of the working face is large, but the periodic weighting of the working face is not obvious. The first collapse step of the immediate roof is 15 m. When mining the upper and lower coal seams, the subsidence of the monitoring point increases significantly at 17.5 and 15 m, respectively. The roof collapse of the lower coal seam occurs 2.5 m ahead of that of the upper coal seam. The hydraulic value of the support, roof fall height, and sloughing depth in the entire working face reach the maximum at the coal pillar, and the extreme points at the coal pillar are relatively concentrated. This research provides some guidance for the safe and efficient mining of extremely close coal seams in the future.

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