Occurrence Characteristic and Mining Technology of Ultra-thick Coal Seam in Xinjiang, China

The scientific and efficient mining of ultra-thick coal seam in Xinjiang, China is faced with the problems of low exploration level and lack of theoretical research on underground mining. This paper studied occurrence characteristic of ultra-thick coal seams in Xinjiang, using field investigation and drilling exploration. Based on the variation law of support load under different roof bearing structure form and development height in multi-layer mining, classification method and mining technology selection of ultra-thick coal seam were put forward. The results indicate that: 1) The ultra-thick coal seams in Xinjiang have a distribution characteristic of more north and less south, more east and less west, mainly concentrate in East Junggar and Turpan-Harmi coalfields. The form of the ultra-thick coal seam has the remarkable characteristic of coal seams merging and bifurcating. 2) The mechanical model of the relationship between the support and surrounding rock under different roof bearing structures is established. At the early stage of multi-layer mining, the support load includes the load caused by rotary subsidence of the blocks that formed the near-stope roof bearing structure and the gravity load of rock blocks under roof bearing structure. At the later stage, the support load is mainly gravity load of loose blocks below the far-stope roof bearing structure. 3) According the roof bearing structure form, ultra-thick coal seam can be divided into three types: no stable bearing structure, (higher) beam bearing structure and arch bearing structure. In order to ensure the stability of near-stope roof bearing structure, backfill mining, longwall mining, and longwall mining early and backfill mining later should be adopted in three types ultra-thick coal seams mining respectively.

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The Study of Key Stratum Location and Characteristics on the Mining of Extremely Thick Coal Seam under Goaf

Advances in Civil Engineering ◽

10.1155/2021/8833822 ◽

2021 ◽

Vol 2021 ◽

pp. 1-9

Author(s):

Gaochuan Guo ◽

Yongkang Yang

Keyword(s):

Coal Seam ◽

Longwall Mining ◽

Maximum Principal Stress ◽

Engineering Practice ◽

Coal Seams ◽

Thick Coal Seam ◽

Key Strata ◽

Key Stratum ◽

Arch Structure ◽

Overlying Strata

The basis of traditional ground pressure and strata control techniques is the key strata theory, wherein the position of the key stratum can easily be determined for coal seams with regular thickness and without goaf. However, in the case of mining ultrathick coal seams underneath goaf, the traditional methods used for the calculation of key stratum position need to be improved in order to account for the additional coal seam thickness and the presence of an upper goaf. This study analyzed the failure height and collapse characteristics of overlying strata during excavation for determining the structure of the failed overlying strata. The results indicate that the intercalation and overlying strata gradually evolve into a large “arch structure” and a small “arch structure” during longwall mining, respectively. A mechanical model of the bearing characteristics of the interlayer key strata structure was established according to the structure of the intercalation rock layer, which is a hinged block structure. The results of the model indicate that the maximum principal stress occurs when the key strata portion of the arch structure bears the overlying load. Consequently, the movement and position of the interlayer key strata can be evaluated throughout the mining process of the ultrathick coal seams underneath goaf. This method was used to determine the position of interlayer key stratum of overlying strata in Xiegou coal mine. And the results agree with that of the engineering practice. The results are significant to determine the key strata position during ultrathick coal seam underneath goaf longwall mining.

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Cooperative Control Mechanism of Long Flexible Bolts and Blasting Pressure Relief in Hard Roof Roadways of Extra-Thick Coal Seams: A Case Study

Applied Sciences ◽

10.3390/app11094125 ◽

2021 ◽

Vol 11 (9) ◽

pp. 4125

Author(s):

Zhe Xiang ◽

Nong Zhang ◽

Zhengzheng Xie ◽

Feng Guo ◽

Chenghao Zhang

Keyword(s):

Coal Seam ◽

Cooperative Control ◽

Field Tests ◽

Surrounding Rock ◽

Deep Hole ◽

Coal Seams ◽

Thick Coal Seam ◽

Structure Damage ◽

Hard Roof

The higher strength of a hard roof leads to higher coal pressure during coal mining, especially under extra-thick coal seam conditions. This study addresses the hard roof control problem for extra-thick coal seams using the air return roadway 4106 (AR 4106) of the Wenjiapo Coal Mine as a case study. A new surrounding rock control strategy is proposed, which mainly includes 44 m deep-hole pre-splitting blasting for stress releasing and flexible 4-m-long bolt for roof supporting. Based on the new support scheme, field tests were performed. The results show that roadway support failure in traditional scenarios is caused by insufficient bolt length and extensive rotary subsidence of the long cantilever beam of the hard roof. In the new proposed scheme, flexible 4-m-long bolts are shown to effectively restrain the initial expansion deformation of the top coal. The deflection of the rock beam anchored by the roof foundation are improved. Deep-hole pre-splitting blasting effectively reduces the cantilever distance of the “block B” of the voussoir beam structure. The stress environment of the roadway surrounding rock is optimized and anchorage structure damage is inhibited. The results provide insights regarding the safe control of roadway roofs under extra-thick coal seam conditions.

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Research on mining technology of extra-thick coal seam under rich water aquifers in a bitter cold steppe region

Land Reclamation in Ecological Fragile Areas ◽

10.1201/9781315166582-63 ◽

2017 ◽

pp. 333-343

Author(s):

J. Fang ◽

D.Z. Gu ◽

Q.S. Li ◽

Z.G. Cao

Keyword(s):

Coal Seam ◽

Mining Technology ◽

Thick Coal Seam ◽

Steppe Region

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Automatic Roadway Backfilling of Caving Gangue for Cutting Roofs by Combined Support on Gob-Side Entry Retaining with No-Pillars: A Case Study

Advances in Materials Science and Engineering ◽

10.1155/2019/8736103 ◽

2019 ◽

Vol 2019 ◽

pp. 1-13

Author(s):

Shengrong Xie ◽

Xiaoyu Wu ◽

Dongdong Chen ◽

Yaohui Sun ◽

Junchao Zeng ◽

...

Keyword(s):

Longwall Mining ◽

Control Process ◽

Coal Pillar ◽

Main Roof ◽

Control Effect ◽

Mining Technology ◽

Thick Coal Seam ◽

Immediate Roof ◽

Seam Mining ◽

And Control

Automatic roadways on gob-side entry retaining with no-pillars are used for longwall mining technology. The mining technology with no-pillars can recover coal pillar resources and reduce the amount and cost of roadway excavations. Automatic roadway technology for cutting roofs by combined support on gob-side entry retaining with no-pillars is adopted for the condition of thick immediate roof and medium-thick coal seam mining, cutting off the immediate roof and the main roof on the gob by combined support. The fractured roof forms gangue blocks to fill the gob and loads the overlying strata. The gangue control system is placed on the roadside, which controls the caving gangue to form a gangue rib. In this paper, the viewpoints and key technologies (the roof-cutting technology, the reinforcement and support technology, the gangue rib control technology, and the auxiliary support technology) of automatic roadway technology for cutting roofs by combined support on the gob-side entry retaining with no-pillars are introduced. Furthermore, the formation and control process are explained. The numerical simulation is used to simulate and analyze the roof hanging and the roof cutting structures. In addition, a field engineering test is performed. The field test shows that automatic roadway technology for cutting roofs by combined support on gob-side entry retaining with no-pillars is feasible. This process uses construction techniques and technologies to meet on-site production needs. The combined support has high resistance strength and is shrinkable. In engineering applications, the combined support has a low damage rate. The deformation of the automatic roadway with gob-side entry retaining is small, and the control effect is significant.

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Surrounding Rock Movement of Steeply Dipping Coal Seam Using Backfill Mining

Shock and Vibration ◽

10.1155/2021/5574563 ◽

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.

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Monitoring strata behavior due to multi-slicing top coal caving longwall mining in steeply dipping extra thick coal seam

International Journal of Mining Science and Technology ◽

10.1016/j.ijmst.2016.11.002 ◽

2017 ◽

Vol 27 (1) ◽

pp. 179-184 ◽

Cited By ~ 16

Author(s):

Dongfeng Yun ◽

Zhu Liu ◽

Wendong Cheng ◽

Zhendong Fan ◽

Dongfang Wang ◽

...

Keyword(s):

Coal Seam ◽

Longwall Mining ◽

Thick Coal Seam ◽

Strata Behavior

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Study on Roof-Coal Caving Characteristics with Complicated Structure by Fully Mechanized Caving Mining

Shock and Vibration ◽

10.1155/2019/6519213 ◽

2019 ◽

Vol 2019 ◽

pp. 1-20 ◽

Cited By ~ 4

Author(s):

Yunpei Liang ◽

Lei Li ◽

Xuelong Li ◽

Kequan Wang ◽

Jinhua Chen ◽

...

Keyword(s):

Coal Seam ◽

Coal Mine ◽

Research Work ◽

Maximum Principal Stress ◽

Complicated Structure ◽

Mining Technology ◽

Thick Coal Seam ◽

Soft Coal ◽

Mining Depth ◽

Arch Forms

With mining technology and mechanization degree being improving, fully mechanized caving mining technology (FCM) has become a main method for thick coal seam extraction in China. However, roof-coal caving characteristics in turn restrict its recovery efficiency, especially for the coal seam with complicated structure (CCS), that is, the coal seam comprises hard or soft coal and gangue. In order to explore the key factors influencing the roof-coal caving and recovery characteristics, related research work has been conducted as follows: firstly, a mechanical model of CCS has been established, which indicates the strength of the coal and gangue will directly affect the roof-coal recovery. Meanwhile, based on the geological settings of Qinyuan coal mine, numerical simulation on roof-coal caving law under different thicknesses of hard or soft coal and gangue has been performed using UDEC software. The results show that the maximum principal stress will increase with the increase of mining depth, making the roof-coal to break easily. Furthermore, the range of the plastic zone of the top coal and the damage degree of the top coal increase with the increase of mining depth. Physical modeling results show that when an extraction-caving ratio is 1, the number of times the coal arch forms is 0.43 at every caving, up to a maximum of 3; the number of times coal arch forms with an extraction-caving ratio of 2 is 4.65 times larger than that with an extraction-caving ratio of 1. The probability of coal arch formation with an extraction-caving ratio of 3 is minimal, about 0.4, which is due to that the arch span is large and the curvature is small, so it is difficult to form a stable arch structure. According to the mechanical characteristics of roof-coal in Qinyuan coal mine, deep-hole blasting technique has been used to reduce the fragments of roof-coal crushed. The results show that this technique can effectively improve the recovery of roof-coal.

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Huge thick conglomerate movement induced by full thick longwall mining huge thick coal seam

International Journal of Mining Science and Technology ◽

10.1016/j.ijmst.2011.12.001 ◽

2012 ◽

Vol 22 (3) ◽

pp. 399-404 ◽

Cited By ~ 4

Author(s):

Liqiang Ma ◽

Xiaoxiang Qiu ◽

Tao Dong ◽

Jixiong Zhang ◽

Yanli Huang

Keyword(s):

Coal Seam ◽

Longwall Mining ◽

Thick Coal Seam

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Study on Overburden Strata Rupture Development Height Rules in Repeated Mining of Thick Coal Seams

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.170-173.279 ◽

2012 ◽

Vol 170-173 ◽

pp. 279-282

Author(s):

Nan Nan Zhao ◽

Yong Jie Yang ◽

Chang Qing Wang

Keyword(s):

Coal Seam ◽

Field Measurement ◽

Development Time ◽

Lower Layer ◽

Coal Seams ◽

Thick Coal Seam ◽

Upper Limit ◽

Mining Conditions ◽

Overburden Strata

Take 3 coal repeated mining of Luxi colliery as research background, overburden strata rupture development rules in repeated mining of thick coal seam were studied by using the methods of field measurement. The results indicate that the height of overburden crack belt reduced along with the increase of goaf development time; the crack belt height of upper layer is 34.73m, the ratio of crack height and mining thickness is 15.1, the crack belt height of lower layer increased to 41.51m, but the increased trend declined, the ratio is only 12.14, the development height after up-layer was excavated is 83.6% of the height after two coalface were excavated. The results have important guiding sense for predicting overburden rupture rules in the similar mining conditions and improving the upper limit.

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