scholarly journals Research on the Deformation and Control Technology of Surrounding Rock in Entry Retaining along the Gob Side

2020 ◽  
Vol 2020 ◽  
pp. 1-18
Author(s):  
Meng Zhang ◽  
Hui He ◽  
Yu Zhang ◽  
Xin Jin ◽  
Xinyu Liang ◽  
...  
Keyword(s):  
Mining Area ◽  
Field Investigation ◽  
Industrial Test ◽  
Surrounding Rock ◽  
Control Technology ◽  
Coal Reserve ◽  
Working Face ◽  
Pillar Mining ◽  
Mining Pressure ◽  
The Stability

This paper studies and introduces the successful case of gob-side entry retaining technology and the typical mining pressure law in Luan mining area, which is the main mining coal seam in Qinshui coalfield. Qinshui coalfield has an estimated coal reserve of 300 billion tons, accounting for 9.58% of the total national coal reserve in China, especially anthracite, chemical coal, and coking coal. The methods of field investigation, theoretical analysis, physical experiment, and industrial test are adopted. Through the field investigation, theoretical analysis, physical experiments, and industrial test, the following conclusions have been drawn in this study: (1) A thorough engineering geological investigation was conducted on the entry retaining along the gob side on noncoal pillar mining working face, which covers multiple periods of mining process including the roadway excavation period, primary mining period, primary mining stability period, and secondary mining influence period. A series of analysis and tests were conducted such as core sampling, rock mechanics property testing, borehole detection, and flexible formwork support evaluation, which laid a foundation for identifying the mining pressure law of gob-side entry retaining by using noncoal pillar mining. (2) The mining pressure law was studied through the collection of the field measurements taken from the entry retaining along the gob side on noncoal pillar mining working face. The keys to achieve the roadway surrounding rock stability through noncoal pillar mining are obtained. According to the study, the stability control of retained roadway surrounding rock mainly depends on the stability of top coal, coal side, and shoulder angle coal. (3) In this study, a roadway reinforcement scheme is proposed to improve the surrounding rock control technology for gob-side entry retaining by noncoal pillar mining, whose effectiveness has been verified by a series of industrial test. Therefore, the wide adoption of the noncoal pillar mining method in Number #3 coal mine can significantly relieve the predicament of coal pressing under a large number of buildings in Luan mining area, which provides insightful guidance to the coal-free pillar mining in the whole Luan mining area.

scholarly journals Rebound Mechanism and Control of the Hard Main Roof in the Deep Mining Roadway in Huainan Mining Area

2021 ◽  
Vol 2021 ◽  
pp. 1-17
Author(s):  
Denghong Chen ◽  
Chao Li ◽  
Xinzhu Hua ◽  
Xiaoyu Lu ◽  
Yongqiang Yuan ◽  
...  
Keyword(s):  
Slope Angle ◽  
Bending Moment ◽  
Main Roof ◽  
Mining Area ◽  
Calculation Model ◽  
Surrounding Rock ◽  
Tensile Failure ◽  
Damage Area ◽  
Critical Range ◽  
Working Face

Taking the occurrence conditions of the hard main roof in the deep 13-1 coal mining roadway in Huainan mining area as the research object, based on the mechanical parameters of the surrounding rock and the stress state of the main roof obtained by numerical simulation, a simply supported beam calculation model was established based on the damage factor D, main roof support reaction RA, RB, and critical range C (9 m) and B (7 m) at the elastoplastic junction of the solid coal side and mining face side (hereinafter referred to as “junction”). Considering that the damage area still has a large bearing capacity, the vertical stress of the main roof at the junction is K1γH (0.05γh, 0.15γh, and 0.25γh) and K2γH (0.01γh, 0.10γh, and 0.2γh). The maximum deflection is 21 mm, 324 mm, and 627.6 mm, respectively. According to the criterion of tensile failure, the maximum bending moment of the top beam is 209 mN·m at the side of the working face 3.1 m away from the roadway side when K1 = 0.15 and K2 = 0.10, and the whole hard main roof is in tensile failure except the junction. To control the stability of the top beam and simplify the supporting reaction to limit the deformation of the slope angle, RC and RD are used to construct the statically indeterminate beam. By adding an anchor cable and advance self-moving support to the roadway side angle, the problem of difficult control of the surrounding rock with a large deformation of the side angle roof is solved, which provides a reference for roof control under similar conditions.

scholarly journals Surrounding Rock Movement of Steeply Dipping Coal Seam Using Backfill Mining

2021 ◽  
Vol 2021 ◽  
pp. 1-17
Author(s):  
Wenyu Lv ◽  
Kai Guo ◽  
Jianhao Yu ◽  
Xufeng Du ◽  
Kun Feng
Keyword(s):  
Numerical Simulation ◽  
Coal Seam ◽  
Surrounding Rock ◽  
Maximum Deflection ◽  
Coal Seams ◽  
Physical Similarity ◽  
Working Face ◽  
Rock Structure ◽  
Backfill Mining ◽  
The Stability

The movement of the overlying strata in steeply dipping coal seams is complex, and the deformation of roof rock beam is obvious. In general, the backfill mining method can improve the stability of the surrounding rock effectively. In this study, the 645 working face of the tested mine is used as a prototype to establish the mechanical model of the inclined roof beam using the sloping flexible shield support backfilling method in a steeply dipping coal seam, and the deflection equation is derived to obtain the roof damage structure and the maximum deflection position of the roof beam. Finally, numerical simulation and physical similarity simulation experiments are carried out to study the stability of the surrounding rock structure under backfilling mining in steeply dipping coal seams. The results show the following: (1) With the support of the gangue filling body, the inclined roof beam has smaller roof subsidence, and the maximum deflection position moves to the upper part of working face. (2) With the increase of the stope height, the stress and displacement field of the surrounding rock using the backfilling method show an asymmetrical distribution, the movement, deformation, and failure increase slowly, and the increase of the strain is relatively stable. Compared with the caving method, the range and degree of the surrounding rock disturbed by the mining stress are lower. The results of numerical simulation and physical similarity simulation experiment are generally consistent with the theoretically derived results. Overall, this study can provide theoretical basis for the safe and efficient production of steeply dipping coal seams.

scholarly journals Study on the Instability Characteristics and Bolt Support in Deep Mining Roadways Based on the Surrounding Rock Stability Index: Example of Pansan Coal Mine

2020 ◽  
Vol 2020 ◽  
pp. 1-16 ◽  
Author(s):  
Jucai Chang ◽  
Kai He ◽  
Zhiqiang Yin ◽  
Wanfeng Li ◽  
Shihui Li ◽  
...  
Keyword(s):  
Coal Mine ◽  
Stability Index ◽  
Surrounding Rock ◽  
Full Length ◽  
Control Effect ◽  
Support Design ◽  
Rock Stability ◽  
Working Face ◽  
The Stability ◽  
Bolt Support

In view of the influence of mining stress on the stability of the surrounding rock of inclined roof mining roadways in deep mines, the surrounding rock stability index is defined and solved based on the rock strength criterion and the stress distribution. The mining roadway of the 17102(3) working face of the Pansan Coal Mine is used as the engineering background and example. The surrounding rock’ stabilities under the conditions of no support and bolt support are analyzed according to the surrounding rock’s stability index and the deformation data. The results show that the areas of low wall and high wall instability are 1.68 m2 and 2.12 m2, respectively, and the low wall is more stable than the high wall; the areas of the roof and floor instability are 0.33 m2 and 0.35 m2, respectively, and the roof and floor are more stable than the two sides. During mining, the area of instability greatly increases at first, then decreases to 0, and reaches a maximum value at the peak of the abutment pressure. The stability of the surrounding rock decreases first and then increases. Compared with the end anchoring bolt support, the full-length anchoring bolt support reduces the area of instability to a greater extent, and the full-length anchoring bolt support effect is better. The surrounding rock in the end anchoring zone and the full-length anchoring zone began to deform significantly at 200 m and 150 m from the working face, respectively. This indicates that the control effect of the full-length anchoring bolt support is better and verifies the rationality of the surrounding rock stability index to describe the instability characteristics. This research method can provide a theoretical reference for analysis of the stability characteristics and support design of different cross-section roadways.

scholarly journals The Stability of Gob-Side Entry Retaining in a High-Gas-Risk Mine

2019 ◽  
Vol 2019 ◽  
pp. 1-12 ◽  
Author(s):  
Junwen Zhang ◽  
Yulin Li
Keyword(s):  
Coal Mines ◽  
Surrounding Rock ◽  
Shanxi Province ◽  
Engineering Practice ◽  
Efficient Production ◽  
Coal Recovery ◽  
Working Face ◽  
Geological Conditions ◽  
The Stability ◽  
Strengthening Technique

There are series of problems faced by most of the coal mines in China, ranging from low-coal recovery rate and strained replacement of working faces to gas accumulation in the upper corner of coalfaces. Based on the gob-side entry retaining at the No. 18205 working face in a coal mine in Shanxi Province, theoretical analysis, numerical simulation, and engineering practice were comprehensively used to study the mechanical characteristics of the influence of the width of the filling body beside the roadway and the stability of surrounding rock in a high-gas-risk mine. The rational width of the filling body beside the roadway was determined, and a concrete roadway-side support with a headed reinforcement-integrated strengthening technique was proposed, which have been applied in engineering practice. The stability of the filling body beside the roadway is mainly influenced by the movement of the overlying rock strata, and the stability of the surrounding rock can be improved effectively by rationally determining the width of the filling body beside the roadway. When the width of the roadway-side filling body is 2.5 m, the surrounding rock convergence of the gob-side entry retaining is relatively small at only 5% of the convergence ratio. It has been shown that the figure for roof separation is relatively low, and strata behaviors are relatively alleviated and gas density do not exceed the limit, which are the best results of gob-side entry retaining. The results of this research can provide theoretical guidance for excavation of coal mines with similar geological conditions and have some referential significance to safety and efficient production in coal mines.

scholarly journals Support design of main retracement passage in fully mechanised coal mining face based on numerical simulation

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Yalong Li ◽  
Mohanad Ahmed Almalki ◽  
Cheng Li
Keyword(s):  
Numerical Simulation ◽  
Coal Mine ◽  
Surrounding Rock ◽  
Control Measures ◽  
Coal Face ◽  
Support Design ◽  
Working Face ◽  
Surrounding Rock Control ◽  
Mining Face ◽  
Mining Pressure

Abstract For the comprehensive mechanised coal mining technology, the support design of the main withdrawal passage in the working face is an important link to achieve high yield and efficiency. Due to the impact of mining, the roof movement of the withdrawal passage is obvious, the displacement of the coal body will increase significantly, and it is easy to cause roof caving and serious lamination problems, and even lead to collapse accidents, which will affect the normal production of the mine. In this paper, the mining pressure development law of the main withdrawal passage support under the influence of dynamic pressure is designed, the most favourable roof failure form of the withdrawal passage is determined, and the action mechanism and applicable conditions of different mining pressure control measures are studied. The pressure appearance and stress distribution in the final mining stage of fully mechanised coal face are studied by numerical simulation. The deformation and failure characteristics and control measures of roof overburden in the last mining stage of fully mechanised coal face are analysed theoretically. Due to the fact that periodic pressure should be avoided as far as possible after the full-mechanised mining face is connected with the retracement passage, some auxiliary measures such as mining height control and forced roof blasting are put forward on this basis. The relative parameters of the main supporting forms are calculated. The main retracement of a fully mechanised working face in a coal mine channel is put forward to spread the surrounding rock grouting reinforcement, reinforcing roof, and help support and improve the bolt anchoring force, the main design retracement retracement channels in the channel near the return air along the trough for supporting reinforcing surrounding rock control optimisation measures, such as through the numerical simulation analysis, the optimisation measures for coal mine fully mechanised working face of surrounding rock is feasible. Numerical simulation results also show that the surrounding rock control of fully mechanised working face of coal mine design improvements, its main retreat channel under the roof subsidence, cribbing shrank significantly lower, and closer, to better control the deformation of surrounding rock, achieved significant effect, to ensure the safety of coal mine main retracement channel of fully mechanised working face support.

scholarly journals Mining-Induced Stress Control by Advanced Hydraulic Fracking under a Thick Hard Roof for Top Coal Caving Method: A Case Study in the Shendong Mining Area, China

Minerals ◽  
2021 ◽  
Vol 11 (12) ◽  
pp. 1405
Author(s):  
Kaige Zheng ◽  
Yu Liu ◽  
Tong Zhang ◽  
Jingzhong Zhu
Keyword(s):  
Stress Transfer ◽  
Mining Area ◽  
Fracture Networks ◽  
Horizontal Fracture ◽  
Hard Roof ◽  
Working Face ◽  
Huge Impact ◽  
Mining Pressure ◽  
Impact Kinetic Energy ◽  
Mining Height

Fully mechanized top-coal caving mining with high mining height, hard roofs and strong mining pressure are popular in the Shendong mining area, China. The occurrence of dynamic disasters, such as rock burst, coal and gas outburst, mine earthquakes and goaf hurricanes during the coal exploitation process under hard roof conditions, pose a threat to the safe production of mines. In this study, the characteristics of overburden fracture in fully mechanized top-coal caving with a hard roof and high mining height are studied, and the technology of advanced weakening by hard roof staged fracturing was proposed. The results show that the hard roof strata collapse in the form of large “cantilever beams”, and it is easy to release huge impact kinetic energy, forming impact disasters. After the implementation of advanced hydraulic fracturing, the periodic weighting length decreases by 32.16%, and the length of overhang is reasonably and effectively controlled. Ellipsoidal fracture networks in the mining direction of the vertical working face, horizontal fracture networks perpendicular to the direction of the working face, and near-linear fracture planes dominated by vertical fractures were observed, with the accumulated energy greatly reduced. The effectiveness of innovation technology is validated, and stress transfer, dissipation and dynamic roof disasters were effectively controlled.

scholarly journals Stability Analysis and Control Technology of Gob-Side Entry Retaining with Double Roadways by Filling with High-Water Material in Gently inclined Coal Seam

2021 ◽  
Author(s):  
Shengrong Xie ◽  
En Wang ◽  
Dongdong Chen ◽  
Hui Li ◽  
Zaisheng Jiang ◽  
...  
Keyword(s):  
Coal Seam ◽  
Good Control ◽  
Active Role ◽  
Simulation Method ◽  
High Water ◽  
Industrial Test ◽  
Surrounding Rock ◽  
Control Technology ◽  
Control Effect ◽  
Support Resistance

Abstract Roadside filling body in traditional gob-side entry retaining (GER) has several shortcomings such as the insufficient support resistance, the inability to adapt to the deformation of surrounding rock and isolate the goaf effectively. Taking the GER with double roadways by filling with 1.8-m-wide high-water material in gently inclined coal seam of Zuozegou mine as a project case, the mechanical model of GER with double roadways in the gently inclined coal seam is constructed, and the reasonable width of the filling body of GER is verified by combining with the peak strength of high-water material. The FLAC3D numerical simulation method is used to study the distribution characteristics of stress and plastic zone of GER after being affected by the mining disturbance, and the failure range of surrounding rock of GER with double roadways is obtained. Based on this, a coupling control technology named anchor cables and bolts in the roof and solid coal + single props in entry-in support and goaf side of the outer roadway + anchor bolts in roadside high-water material + short anchor cables below the filling body is proposed and conducted in industrial test. Through the coupling methods of arranging borehole peeping and observing the convergences of surrounding rock, the stability of GER with double roadways is analyzed. The results show that GER with double roadways by filling with 1.8-m-wide high-water material has good control effect. The above research has played an active role in promoting the application of high-water material in roadside filling of GER.

scholarly journals The Research on Stability of Surrounding Rock in Gob-side Entry Driving in Deep and Thick Seam

2021 ◽  
Author(s):  
jianjun SHI ◽  
Feng Jicheng ◽  
Peng Rui ◽  
Zhu Quanjie
Keyword(s):  
Stability Study ◽  
Surrounding Rock ◽  
Support Pressure ◽  
Thick Coal Seam ◽  
Thick Seam ◽  
Working Face ◽  
Pressure Area ◽  
Roadway Support ◽  
The Stability ◽  
Bolt Steel

Abstract The gob-side entry driving is driving in low pressure area, which bears less support pressure and is easy to maintain, so it is widely used. Taking the gob-side entry driving in thick coal seam of Dongtan Coal Mine as an example, the reasonable size of pillar and the section of roadway are numerically simulated by combining numerical with measurement, and the roadway support is designed. According to the distribution of lateral stress in working face, eight pillars of different sizes are designed. By simulating and comparing the stress distribution of surrounding rock and the development range and shape of plastic zone in different positions, the pillar size of gob-side entry driving is optimized to be 4.5m. According to the results of optimization of roadway section, the section of straight wall semi-circular arch roadway is adopted. According to the analysis, the roadway is supported by bolt + steel mesh + anchor cable. By observing the stability of roadway, it provides experience for the stability study of roadway the gob-side entry driving with small pillar in thick seam.

scholarly journals Stability Analysis of the Entry in a New Mining Approach Influenced by Roof Fracture Position

2019 ◽  
Vol 11 (22) ◽  
pp. 6349
Author(s):  
Jun Yang ◽  
Hongyu Wang ◽  
Yajun Wang ◽  
Binhui Liu ◽  
Shilin Hou ◽  
...  
Keyword(s):  
Coal Pillar ◽  
Main Roof ◽  
Surrounding Rock ◽  
Fracture Position ◽  
Solid Coal ◽  
Rock Structure ◽  
Temporary Support ◽  
Coal Wall ◽  
Pillar Mining ◽  
The Stability

Non-coal pillar mining with roadway formed automatically (RFANM) is a new mining approach, which demonstrates revolutionary significance because it does not require making roadway before mining and coal pillar retaining. In order to explore the stability of the surrounding rock structure in RFANM, the deformation of the surrounding rock was theoretically analyzed and simulated based on three different fracture positions of the main roof. It was concluded that reasonable control of temporary support strength in roadway is of great importance to control the deformation of the entry. The deformation process of surrounding rock under different fracture positions in RFANM was simulated by using the Universal Discrete Element Code (UDEC). The results of the numerical simulation showed that the main roof was fractured at the solid coal side or gob side; the deformation of the roadway was small. The fracture condition of the main roof at the gob side required a higher effect of roof slitting or temporary support from the roadway. Through drilling and peeping at the retained roadway, it was judged that the main roof was broken inside the coal wall. Field monitoring results revealed that the deformation of the roadway can be effectively controlled.

Experimental Analysis on Microstructure and Mineral Composition of Jurassic Soft Rock in Shajihai Mining Area of Xinjiang

2013 ◽  
Vol 353-356 ◽  
pp. 24-27
Author(s):  
Xiao Lei Wang ◽  
Shun Xi Yan ◽  
Hai Qiao Wen
Keyword(s):  
Mineral Composition ◽  
Soft Rock ◽  
Mining Area ◽  
Sem Analysis ◽  
Surrounding Rock ◽  
Test Results ◽  
X Ray Diffraction ◽  
Component Content ◽  
The Stability ◽  
Soft Rock Roadway

In order to find out themicroscopic structure and determine mineral composition and relative content ofroadway soft rock in Shajihai mining area, this paper carried out experimentsof scanning electron microscope (SEM) analysis and X-ray diffraction analysis.SEM test results show that the microstructure of the surrounding rock isgenerally poor and joint, crack, pore are developed. The crack is easy toexpand under the effect of surrounding rock pressure and water, which makesrock mass more broken and greatly reduces the stability of surrounding rock.X-ray diffraction analysis test shows that the component content of clayminerals in the surrounding rock is high. Clay mineral in mudstone containsmontmorillonite and content of illite/smectite mixed layer is relativelyhigher, up to 45%. In conclusion, soft rock roadway of Shajihai mine areabelongs to the typical swelling-jointed compound soft rock. The targeted andreasonable compound transformation technology and coupling support measuresmust be adopted when supporting.

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