scholarly journals Pressure Relief by Blasting Roof Cutting in Close Seam Group Mining under Thick Sandstone to Enhance Gas Extraction for Mining Safety

Processes ◽  
2021 ◽  
Vol 9 (4) ◽  
pp. 603
Author(s):  
Kui Gao ◽  
Ping Huang ◽  
Ze-Gong Liu ◽  
Jian Liu ◽  
Fei Wang ◽  
...  
Keyword(s):  
Blast Hole ◽  
Thick Layer ◽  
Mine Pressure ◽  
Gas Extraction ◽  
Coal Face ◽  
Pressure Relief ◽  
Excessive Pressure ◽  
Gas Concentration ◽  
Mining Safety ◽  
High Level

Close seam group mining under thin immediate roofs and thick sandstone walls is typically performed with a strong mine pressure and gas concentration, which pose considerable risks to miners. In this study, the mechanism of pressure relief and permeability enhancement to enhance gas extraction for mining safety through blasting roof cutting were investigated through theoretical analyses, numerical simulations, and laboratory tests. The results revealed that, near the blast-hole, which produced numerous cracks, blasting disturbed the integrity of the thick-layer roofs and redistributed the stress near the blast-hole, which prevented violent mine pressure caused by excessive fracture distances on the thick and hard roofs, reduced the additional load on the support, increased vertical gas migration, and ameliorated the effect of gas drainage caused by high-level boreholes. The field applications of forced roof cutting through deep-hole blasting in the II 7224N face of the Renlou coal mine (Huaibei, Anhui, PR China) demonstrated that the occurrence of excessive pressure on the fully mechanized mining hydraulic support was prevented. The gas extraction volume of high-level boreholes was maintained at 6–8 m3/min; the extraction concentration was stable at approximately 35%; and the gas concentration in the upper corner of the coal face was lessened from 7% to <1%, which ensured normal mining in the coal face. The current results can provide data reference and a theoretical basis for roof management and gas control of the same type of coal face.

scholarly journals A Novel Hydraulic Mode to Promote Gas Extraction: Pressure Relief Technologies for Tectonic Regions and Fracturing Technologies for Nontectonic Regions

2019 ◽  
Vol 9 (7) ◽  
pp. 1404 ◽  
Author(s):  
Shaojie Zuo ◽  
Zhaolong Ge ◽  
Zhe Zhou ◽  
Li Wang ◽  
Hanyun Zhao
Keyword(s):  
High Efficiency ◽  
Coal Mines ◽  
Clean Energy ◽  
Extraction Time ◽  
Efficient Production ◽  
Gas Extraction ◽  
Coal Seams ◽  
Pressure Relief ◽  
Gas Concentration ◽  
Coal Roadway

Extraction of gas (coalbed methane) produces clean energy and can ensure that coal mines maintain high-efficiency production. The currently available coal seam permeability enhancing technologies and modes have certain application restrictions. Therefore, a novel mode is proposed to promote gas extraction. This mode divides complex coal seams into tectonic regions and nontectonic regions based on geological structures. Then, the characteristics of different regions are matched with the advantages of different hydraulic technologies; thus, pressure relief technologies are proposed for tectonic regions, and fracturing technologies are proposed for nontectonic regions. The permeability of coal seams will be sharply increased without leaving unfractured areas. This mode will promote the effectiveness of gas extraction, shorten the extraction time, and ensure safe and efficient production in coal mines. A field application shows that this mode has a better effect than slotted directional hydraulic fracturing technology (SDHFT). The gas concentration and pure gas flow were increased by 47.1% (up to 24.94%) and 44.6% (up to 6.13 m3/min), respectively, compared to SDHFT over 9 months. The extraction time was reduced by 4 months. This mode reduced the number of times that gas concentration exceeded government standards during coal roadway excavation, and the coal roadway excavation speed was increased by 16% (up to 158 m/month).

scholarly journals Controlling mine pressure by subjecting high-level hard rock strata to ground fracturing

2021 ◽  
Author(s):  
Rui Gao ◽  
Tiejun Kuang ◽  
Yanqun Zhang ◽  
Wenyang Zhang ◽  
Chunyang Quan
Keyword(s):  
Energy Release ◽  
Physical Simulation ◽  
Hard Rock ◽  
Structural Characteristics ◽  
Effective Control ◽  
Mine Pressure ◽  
Control Effect ◽  
Propagation Length ◽  
Ground Pressure ◽  
High Level

AbstractWhen mining extra-thick coal seams, the main cause of strong ground pressure are the high-level thick and hard strata, but as yet there is no active and effective control technology. This paper proposes the method of subjecting hard roofs to ground fracturing, and physical simulation is used to study the control effect of ground fracturing on the strata structure and energy release. The results show that ground fracturing changes the structural characteristics of the strata and reduces the energy release intensity and the spatial extent of overburden movement, thereby exerting significant control on the ground pressure. The Datong mining area in China is selected as the engineering background. An engineering test was conducted on site by ground horizontal well fracturing, and a 20-m-thick hard rock layer located 110 m vertically above the coal seam was targeted as the fracturing layer. On-site microseismic monitoring shows that the crack propagation length is up to 216 m and the height is up to 50 m. On-site mine pressure monitoring shows that (1) the roadway deformation is reduced to 100 mm, (2) the periodic weighting characteristics of the hydraulic supports are not obvious, and (3) the ground pressure in the working face is controlled significantly, thereby showing that the ground fracturing is successful. Ground fracturing changed the breaking characteristics of the high-level hard strata, thereby helping to ameliorate the stress concentration in the stope and providing an effective control approach for hard rock.

scholarly journals Roadway Surrounding Rock under Multi-Coal-Seam Mining: Deviatoric Stress Evolution and Control Technology

2020 ◽  
Vol 2020 ◽  
pp. 1-18
Author(s):  
Dongdong Chen ◽  
En Wang ◽  
Shengrong Xie ◽  
Fulian He ◽  
Long Wang ◽  
...  
Keyword(s):  
Plastic Zone ◽  
Coal Seam ◽  
Coal Pillar ◽  
Surrounding Rock ◽  
Deviatoric Stress ◽  
Mine Pressure ◽  
Coal Face ◽  
Surrounding Rock Control ◽  
Seam Mining ◽  
Peak Value

Multi-coal-seam mining creates surrounding rock control difficulties, because the mining of a coal face in one seam can affect coal faces in another. We examine the effects of multi-coal-seam mining on the evolution of the deviatoric stress distribution and plastic zone in the roadway surrounding rock. In particular, we use numerical simulation, theoretical calculation, drilling detection, and mine pressure observation to study the distribution and evolution characteristics of deviatoric stress on Tailgate 8709 in No. 11 coal seam in Jinhuagong mine when the N8707 and N8709 coal faces in No. 7-4 coal seam and the N8707 and N8709 coal faces in No. 11 coal seam are mined. The evolution laws of deviatoric stress and the plastic zone of roadway surrounding rock in the advance and behind sections of the coal face are studied, and a corresponding control technology is proposed. The results show that the peak value of deviatoric stress increases with the advance of the coal face, and the positions of the peak value of deviatoric stress and the plastic zone become deeper. The deflection angle of the peak stress after mining at each coal face and the characteristics of the peak zone of deviatoric stress and the plastic zone of the roadway surrounding rock under the disturbance of multi-coal-seam mining are determined. In conclusion, the damage range in the roadway roof in the solid-coal side and coal pillar is large and must be controlled. A combined support technology based on high-strength and high pretension anchor cables and truss anchor cables is proposed; long anchor cables are used to strengthen the support of the roadway roof in the solid-coal side and coal pillar. The accuracy of the calculated plastic zone range and the reliability of the combined support technology are verified through drilling detection and mine pressure observation on site. This research can provide a point of reference for roadway surrounding rock control under similar conditions.

scholarly journals Study on Borehole Arrangement Methods for Gas Extraction by Hydraulic Slotting in Long-Distance Through-Coal Seam Tunnel

Geofluids ◽  
2020 ◽  
Vol 2020 ◽  
pp. 1-8
Author(s):  
Cunfang Zhu ◽  
Shuang Cai
Keyword(s):  
Numerical Simulation ◽  
Coal Seam ◽  
Simulation Models ◽  
Gas Production ◽  
Gas Extraction ◽  
Long Distance ◽  
Pressure Relief ◽  
Coal Deposits ◽  
Geological Conditions ◽  
Rapid Pressure

How to quickly eliminate outburst in long-distance through-coal seam tunnels is one of the major challenges faced by the tunnel industry in mountainous areas. Compared with coal mine rock crosscut coal uncovering, the work surrounding the rock of through-coal seam tunnels has a high degree of breakage, large cross-section of coal uncovering, and tight time and space. In this paper, a method of networked slotting in long-distance through-coal seam tunnels for rapid pressure relief and outburst elimination is proposed. Based on this method, the corresponding mathematical governing equations and numerical simulation models have been established. The optimal borehole arrangement spacing and the slot arrangement spacing obtained by numerical optimization are 2.85 m and 3.1 m, respectively. Field gas production data of through-coal seam tunnels show that compared with the traditional dense-borehole gas extraction, the method of networked slotting in long-distance through-coal seam tunnels for rapid pressure relief and outburst elimination can shorten the extraction time by about 66%, the net quantity of peak extraction is increased by 3.55 times, and the total quantity of gas extraction when reaching the outburst prevention index is increased by 1.26 times, which verifies the feasibility of this method and the reliability of numerical simulation results. This study could be used as a valuable example for other coal deposits being mined under similar geological conditions.

Experimental Study on Deep Borehole Pre-Cracking Blasting of Drilling through Strata at Low Permeability Seam

2013 ◽  
Vol 868 ◽  
pp. 339-342
Author(s):  
Jian Liu ◽  
Qian Le
Keyword(s):  
Coal Seam ◽  
Control Area ◽  
Low Permeability ◽  
Gas Extraction ◽  
Test Results ◽  
Deep Borehole ◽  
Coal Seam Gas ◽  
Gas Concentration ◽  
Working Face ◽  
Outburst Coal Seam

In the process of roadway excavation in the low permeability outburst coal seam, with drilling through strata in the bottom drainage roadway extracting coal seam gas of control area. In order to improve extraction effect, the method that deep borehole pre-cracking blasting is used to increase the permeability of coal in the drilling through strata seam segment is proposed. The calculation formula on crushing circle and crack circle radius of deep borehole pre-cracking blasting are derived, and the effective loosening radius of blasting is calculated in theory, the research achievements are applied to field test, the test results show that deep borehole pre-cracking blasting permeability improvement technology is carried out in the drilling through strata of the low permeability outburst coal seam, the permeability of coal seam is improved by 180 times, the gas extraction scalar is raised by 8-10 tomes, during the process of roadway excavation, gas concentration of the working face is 0.2%-0.3%, and tunneling footage is increased by 2 times.

The Research Progress of Coal and Gas Co-Mining

2012 ◽  
Vol 524-527 ◽  
pp. 489-493 ◽  
Author(s):  
Li Ming Ying ◽  
Jie Chen ◽  
Chao Du ◽  
Lin Xiang Pang ◽  
Yong Jiang Wen
Keyword(s):  
Coal Mine ◽  
Greenhouse Gas Emission ◽  
Research Progress ◽  
Coal Bed ◽  
Gas Extraction ◽  
Gas Emission ◽  
Extraction Technology ◽  
Pressure Relief ◽  
Adjacent Layer ◽  
Improve Energy Efficiency

The coal bed methane is an important part of the Chinese energy. To finding some effect ways to collect gas during the coal mining process will increasing the using rate of coal mine and reducing greenhouse gas emission. The most effective way is coal and gas co-mining, and the main technology of the coal and gas co-mining are gas pre-extraction before mining, gas extraction of pressure relief, gas extraction of adjacent layer, gas extraction of goaf and top fractured zone, Gas extraction of excavation roadway and so on. Based on the technique system of coal and gas co-mining and the key problems existing in coal and gas extraction technology, to improve energy efficiency and reduce coal mine disaster.

scholarly journals RESULTS OF NEW STUDIES OF EARLY NEOLITHIC LAYERS AT RAKUSHECHNYY YAR (ROSTOV REGION)

2021 ◽  
pp. 27-43
Author(s):  
А. Н. Мазуркевич ◽  
Е. В. Долбунова ◽  
В. В. Цыбрий ◽  
А. В. Цыбрий ◽  
Я. Шманда ◽  
...  
Keyword(s):  
Thick Layer ◽  
Lake Basin ◽  
Buried Soils ◽  
Early Neolithic ◽  
Human Occupation ◽  
Rostov Region ◽  
Short Period ◽  
High Level ◽  
Littoral Area ◽  
Insight Into

Ракушечный Яр - уникальный стратифицированный памятник VII/VI тыс. до н. э. - раннего Средневековья - характеризуется сложной стратиграфией и палеорельефом, наличием погребенных почв и культурных слоев. Планомерные раскопки памятника проводились в 1960-1970 гг. и возобновлены в 2008 г. В результате комплексных археологических и геологических исследований выявлены особенности культурных слоев, позволившие выстроить микрохронологию этого памятника, где отдельные слои формировались за очень короткое время. Ракушечный Яр представляет свидетельства разновременного и последовательного заселения человеком прибрежной зоны. Раскопанные части стоянок, возможно, были специализированными местами использования водных ресурсов. Ранненеолитическое поселение в непосредственной близости от озера, возникшего примерно в сер. VIII тыс. до н. э., появилось около 5600 л. до н. э. В рамках отдельных горизонтов отмечены платформы и/или кучи раковин Unio и Viviparus, перекрытые тонкими (1-3 см) прослойками песка и суглинка и мощным слоем белого стерильного аллювиального песка. Такая последовательность отложений могла возникнуть в прибрежной озерной зоне во время трансгрессий и регрессий. Датировки отдельных слоев указывают на узкий хронологический интервал их сложения, что позволяет предполагать высокий уровень минеральных отложений в озерной котловине. По всей видимости, накопление (около 2 м) ранненеолитических слоев происходило в течение нескольких десятилетий. В статье будут рассмотрены особенности образования культурных и литологических слоев для временного среза раннего неолита. Rakushechnyy Yar is a unique stratified site dating to 7000-6000 BC characterized by complex stratigraphy, presence of buried soils and occupation layers. Consistent excavations of the site were first carried out in 1960-1970 and were then resumed in 2008. Comprehensive geoarchaeological studies helped examine specific traits of its occupation layers providing insight into microchronology of the site where some layers were formed during a very short period of time. Rakushechnyy Yar contains evidence of consistent human occupation of the littoral area in different periods of time. Most likely, the excavated sections of the sites were specialized places where water resources were used. The Early Eneolithic settlement near the lake that had been formed around mid-8th mill. BC appeared around 5600 BC. Platforms and/or bunches of Unio and Viviparus shells overlain with thin (1-3 cm) sand and loam layers and a thick layer of white sterile alluvial sand were recorded in some horizons. This sequence of deposits could occur in the littoral lacustrine area during transgressions and regressions. Dating of several layers point to a narrow chronological interval of their formation suggesting a high level of minerogenetic deposits in the lake basin. Apparently, it took several decades of these minerogenetic deposits of the Early Neolithic layers (around 2 m thick) to form.

scholarly journals Prediction of Coal Face Gas Concentration by Multi - Scale Selective Ensemble Hybrid Modeling

2014 ◽  
Vol 7 (2) ◽  
pp. 53-59 ◽  
Author(s):  
WU Xiang ◽  
◽  
YANG Zhong - ru ◽  
Zhang Li ◽  
Pilati Silvia ◽  
...  
Keyword(s):  
Hybrid Modeling ◽  
Coal Face ◽  
Gas Concentration ◽  
Multi Scale ◽  
Selective Ensemble
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