scholarly journals Quantitative Evaluation of Top Coal Caving Methods at the Working Face of Extra-Thick Coal Seams Based on the Random Medium Theory

2021 ◽  
Vol 2021 ◽  
pp. 1-9
Author(s):  
Shi Jiulin ◽  
Zhang Quntao ◽  
Gao Xiaojin ◽  
Xue Jisheng
Keyword(s):  
Random Media ◽  
Production Efficiency ◽  
Random Medium ◽  
Field Tests ◽  
Coal Seams ◽  
Medium Theory ◽  
Working Face ◽  
Coal Particles ◽  
Geological Conditions ◽  
Coal Rock

Adopting an effective top coal caving method is the key to enhancing coal recovery and reducing gangue content for the fully mechanized top coal caving working face with extra-thick coal seams. In this study, the movement of coal particles generated during top coal caving is considered to follow a normal distribution. Then, the caving body and coal-rock settlement along the working face during the caving process are studied based on both the random media theory and probability theory. Accordingly, the optimal caving interval and caving sequences are determined, and a novel interval symmetrical coal caving method is proposed. The proposed method is systematically verified with results from physical similarity tests, and different caving methods are assessed by field tests. The results show the following: (1) The coal-rock settlement and the caving body demonstrate clear axial symmetrical features along the working face; the size of the caving body increases as the caving height grows and its shape turns progressively from semicircular to semielliptical with a lower foot of the coal-rock settlement. (2) The caving interval is derived using the sum of the radii of the coal-rock settlement curves formed by the two largest caving bodies. (3) The symmetrical caving approach provides a symmetrical space for the subsequent movement of the broken top coal, which enables a uniform development of the caving body. (4) Compared with the traditional sequential coal caving method with the same number of supports, the interval symmetrical caving method results in a 21.7% of coal production increase, 17% caving rate promotion, and a shortened caving time by 23.4%. (5) The interval symmetrical caving method is found to improve the controllability of the caving process at the fully mechanized top coal caving working face. In general, this work presents a theoretical approach to select the optimal caving methods for the fully mechanized caving working face in extra-thick coal seams for an improved production efficiency of the work face. The results of this study can also provide theoretical significance and referencing value for quantitative analyses of the coal caving methods for work faces with similar geological conditions.

scholarly journals Loading Performance of a Novel Shearer Drum Applied to Thin Coal Seams

Energies ◽  
2021 ◽  
Vol 14 (2) ◽  
pp. 358
Author(s):  
Kuidong Gao ◽  
Xiaodi Zhang ◽  
Liqing Sun ◽  
Qingliang Zeng ◽  
Zhihai Liu
Keyword(s):  
Rotational Speed ◽  
Production Efficiency ◽  
Loading Rate ◽  
Positive Impact ◽  
Structural Parameters ◽  
Helix Angle ◽  
Structure Design ◽  
Coal Seams ◽  
Coal Particles ◽  
Relationship Of

The poor loading performance of shearer drums restricts the development and production efficiency of coal in thin coal seams. Changing operation and structural parameters can improve the drum’s loading performance to some extent, but the effect is not obvious. A two-segment differential rotational speed drum (TDRSD) was proposed after analyzing the drum’s influence mechanism on coal particles. To further reveal the drum’s coal loading principle, the velocity, particles distribution, and loading rate were analyzed. The effect of the matching relationship of the rotational speed and helix angle between the front and rear drum are also discussed. The results show that a lower front drum rotational speed had a positive impact on improving the loading performance, and the loading rate first increases and then decreases with the increase in rear drum rotational speed. The optimal loading performance was obtained in the range 60–67.5 rpm. The front drum’s helix angle had no evident effect on loading performance, and the loading rate increase with the increase in the rear drum’s helix angle. The results provide a reference and guidance for operation parameters selection, structure design, and drum optimization.

scholarly journals Optimizing Simulation and Analysis of Automated Top-Coal Drawing Technique in Extra-Thick Coal Seams

Energies ◽  
2020 ◽  
Vol 13 (1) ◽  
pp. 232 ◽  
Author(s):  
Qunlei Zhang ◽  
Ruifu Yuan ◽  
Shen Wang ◽  
Dongyin Li ◽  
Huamin Li ◽  
...  
Keyword(s):  
Numerical Models ◽  
Time Estimation ◽  
Engineering Practice ◽  
Coal Seams ◽  
Control Approach ◽  
Working Face ◽  
Geological Conditions ◽  
Round Number ◽  
Element Approach ◽  
Drawing Technique

A particle element approach based on continuum-discontinuum element method (CDEM) is applied to optimize the automated top-coal drawing techniques in extra-thick coal seams. Numerical models with 100 drawing openings are created according to the field engineering geological conditions of Tongxin coal mine in China. An automated coal drawing control approach in numerical modelling based on time criterion is proposed. The rock mixed rate, top-coal recovery rate and the variance of the drawn top coal amount are counted and set as the statistical indicators to evaluate the top-coal drawing techniques. The traditional top-coal drawing criterion, “rocks appear, close the opening”, leads to low recovery of top coal and waste of coal resources in extra-thick coal seams, significantly weakening the transport stability and efficiency of the scraper conveyer. A three-round unequal time top-coal drawing technique is proposed for automated top-coal drawing. Three drawing openings, corresponding to the three top-coal drawing rounds respectively, are working at the same time; in each round, the top-coal drawing sequence is from the first drawing opening at one end of the working face to last drawing opening at another end; the drawing time of each round is not equal and increases with the round number. The numerical inversion approach of iteration steps can be used for real top-coal drawing time estimation and automated drawing process design to achieve a better top coal drawing effect, while the exact time for each drawing round still needs to be corrected by engineering practice.

scholarly journals Strata Movement of the Thick Loose Layer under Strip-Filling Mining Method: A Case Study

2021 ◽  
Vol 11 (24) ◽  
pp. 11717
Author(s):  
Qingliang Chang ◽  
Xingjie Yao ◽  
Qiang Leng ◽  
Hao Cheng ◽  
Fengfeng Wu ◽  
...  
Keyword(s):  
Tensile Stress ◽  
Field Tests ◽  
Control Factor ◽  
Working Face ◽  
Body Strength ◽  
Geological Conditions ◽  
Thin Bedrock ◽  
Loose Layer ◽  
Fourth Round

Filling mining plays an important role in controlling surface subsidence. To study the movement of overburdened rock in filling mining under thick loose layers, a numerical simulation combing field measurement in CT30101 working face in the Mahuangliang coal mine was tested. The results show that different filling rates and filling body strength have different influences on roof and surface movement. The filling rate has a greater impact, which is the main control factor. The filling stress and roof tensile stress decrease gradually with roadway filling. The filling body stress and roof tensile stress in the first and second rounds are far greater than in the fourth round. After the completion of filling, the first and second round of filling bodies mainly bear the overburden, and the total deformation of the surrounding rock of the main transport roadway is very small, and therefore the displacement of the overburdened rock is controllable. The field monitoring results also show that the overburdened rock became stable after several fillings rounds. Combing the numerical modeling and field tests results, this study can be a guideline for similar geological conditions especially for coal mining under thick loose layers and thin bedrock.

scholarly journals Study on the Influence of Snow Melt Water in Tianshan Mountains on the Water Filling of Yili No. 1 Mine and the Prevention of Water Hazards

2021 ◽  
Author(s):  
Lin Feng ◽  
Yajun Sun ◽  
Chenghang Zhang ◽  
Zhimin Xu ◽  
Zewen Yuan ◽  
...  
Keyword(s):  
Treatment Plan ◽  
Water Discharge ◽  
Water Inrush ◽  
Tianshan Mountains ◽  
Tianshan Mountain ◽  
Coal Seams ◽  
Water Release ◽  
Working Face ◽  
Geological Conditions ◽  
Water Filling

Abstract Yili No.1 Mine locates opposite Tianshan Mountain in Yili Prefecture, Xinjiang. The main coal seams are No.3 and No.5 coal seams. The alluvial strata cover the surface of the minefield in the piedmont of the Tianshan Mountains. Snowmelt in the Tianshan Mountains is an essential source of replenishment for surface water and alluvial strata in the basin. Due to the particular diagenetic environment and geological conditions, coal mining is mainly affected by weakly cemented sandstone aquifers on the roof and floor. To solve the water hazard problems of the No.3 coal roof and the No.5 coal floor faced by the mine, we take the 1520w first mining face of Yili No.1 Mine as the research object. And through drilling and on-site water release tests, the threat of water inrush from the working face of the study area and the treatment plan are analyzed. The results show that the Quaternary aquifer in the study area is thin in thickness and fast in velocity. Therefore, it mainly flows through the site in the form of “slope transit flow”, which has little impact on the roof water filling of the No.3 coal seams. In addition, the floor water discharge test proved that the sandstone aquifer of the No.5 coal seam floor has the characteristics of dredging. To eliminate the threat of water inrush during the next mining step in the mine, we proposed arranging an “L”-shaped drainage project in the first working face. And the dredging effect was pronounced and can ensure the safety of mining. At the same time, it has essential reference significance for the mining work of other similar mines in the western region.

Recent Patents on Thin Coal Seam Mining Equipment

2020 ◽  
Vol 13 (2) ◽  
pp. 99-108
Author(s):  
Yanxiang Wang ◽  
Daolong Yang ◽  
Bangsheng Xing ◽  
Tingting Zhao ◽  
Zhiyi Sun ◽  
...  
Keyword(s):  
Coal Seam ◽  
Underground Space ◽  
Mining Method ◽  
Mining Equipment ◽  
Coal Seams ◽  
Thin Coal Seam ◽  
Recoverable Reserves ◽  
Working Face ◽  
Geological Conditions ◽  
Seam Mining

Background:: China's thin and extremely thin coal seam resources are widely distributed and rich in reserves. These coal seams account for 20% of the recoverable reserves, with 9.83 billion tons of industrial reserves and 6.15 billion tons of recoverable reserves. Objective: Due to the complex geological conditions of the thin coal seam, the plow mining method cannot be effectively popularized, and the drum mining method is difficult to be popularized and applied in small and medium-sized coal mines, so it is necessary to find other more advantageous alternative mining methods. Methods: The equipment integrates mining operations, conveying operations, and supporting operations, and is suitable for mining short and extremely thin coal seam with a height of 0.35m-0.8m and width of 2m-20m. It has the advantages of the low body of the shearer, no additional support on the working face, and small underground space. The mining efficiency of thin coal seam and very thin coal seam can be improved and the mining cost can be reduced. Results: Thin coal seam shear mining combines mining, conveying, and supporting processes together and has the advantages of a low fuselage, no extra support required for the working face, and feasibility in a small underground space. Conclusion: The summarized mining method can improve the mining efficiency of thin and extremely thin coal seams, reduce mining costs, and incorporate green mining practices, which take both mining economy and safety into account.

scholarly journals Justification of Spatially-Planned Solutions and Determination of the Dimension Block in the Working of the Medium Thick Inclined Coal Seams with the Room and Pillar System

2018 ◽  
Vol 41 ◽  
pp. 01024
Author(s):  
Thang Pham Duc ◽  
Anh Phan Tuan ◽  
Viktor Vitcalov ◽  
Phuc Le Quang
Keyword(s):  
Technological Parameters ◽  
Coal Seams ◽  
Coal Basin ◽  
Working Face ◽  
Geological Conditions ◽  
Rational Length ◽  
Working Out ◽  
Quang Ninh ◽  
Excavation Area

Technological parameters for working out of the medium thick inclined coal seams with a diagonal arrangement of a line of a working face. An analysis of the constraints that apply the technology and the complexities of the mining and geological conditions of the Quang Ninh coal basin. The possibility and expediency of using the foreign experience of working out of the medium thick inclined coal seams in the mines of Vietnam and justification of spatially-planned solutions for working. The scheme of preparation and working out of the excavation area is given in view of the technological features in difficult mining and geological conditions, using the room and pillar system and determination of the rational length of the block along the strike.

scholarly journals A Case Study of Cyclic Top Coal Weakening Process Based on Highly Tough Coal Seam with Partings

2021 ◽  
Vol 2021 ◽  
pp. 1-17
Author(s):  
Zhaopeng Wu ◽  
Junhui Wang ◽  
Zhijun Wan ◽  
Jingyi Cheng ◽  
Luchang Xiong ◽  
...  
Keyword(s):  
Water Injection ◽  
Performance Testing ◽  
Engineering Practice ◽  
Coal Seams ◽  
The Sustainable Development ◽  
Mine Fire ◽  
Working Face ◽  
Geological Conditions ◽  
Coal Resource ◽  
Special Complex

The top coal weakening process is an effective mean to increase the coal output, reduce the coal resource waste, and promote the sustainable development in a mine. The conventional blast weakening process and water injection weakening process are more widely applied in fully mechanized caving mining of hard thick coal seams, but under some special complex geological conditions, no desirable performance has been achieved in top coal weakening by one weakening process alone after substantial investment in capital and equipment. In the context of highly tough top coal with partings at working face 110501 for fully mechanized top coal caving mining in Yushutian Coal Mine, effects of parting band and high toughness on top coal breaking were studied in terms of mechanism and extent, a multifunctional compound drilling field integrating blast weakening, water injection weakening, and gas extraction was purposefully designed, and a cyclic top coal weakening process for highly tough coal seams with partings was proposed. Engineering practice and performance testing show that degree of fragmentation and mobility of top coal was improved, mean top coal recovery ratio at the working face increased by about 35%, coal resource waste decreased, and potential risks of gas explosion and mine fire were eliminated, which provides reference for top coal weakening process under similarly complex engineering conditions.

scholarly journals Gob-Side Entry Retained with Soft Roof, Floor, and Seam in Thin Coal Seams: A Case Study

2020 ◽  
Vol 12 (3) ◽  
pp. 1197 ◽  
Author(s):  
Zhijun Tian ◽  
Zizheng Zhang ◽  
Min Deng ◽  
Shuai Yan ◽  
Jianbiao Bai
Keyword(s):  
Mining Industry ◽  
Coal Pillar ◽  
Surrounding Rock ◽  
Engineering Practice ◽  
Mine Pressure ◽  
Coal Seams ◽  
Rock Stability ◽  
Working Face ◽  
Geological Conditions ◽  
Surrounding Rock Control

Gob-side entry retained technology is of great significance to develop coal mining industry sustainably, which can improve the coal recovery rate by mining without the coal pillar. However, scholars and researchers pay little attention to the gob-side entry retained with soft roof, floor, and seam in thin coal seams. In this study, the difficulties and key points of surrounding rock control for gob-side entry retained with soft roof, floor, and seam in thin coal seams were firstly proposed. Secondly, the mechanical model of the interaction between the roadside backfill body and the roof for gob-side entry retained with soft roof, floor, and seam in thin coal seams was established, and the relevant parameters were designed. Finally, the above results were verified by the engineering practice of gob-side entry retained technology and the monitoring of mine pressure on the 1103 working face of the Heilong Coal Mine. Moreover, the effect factors of surrounding rock stability for gob-side entry retained with soft roof, floor, and seam in thin coal seams were discussed using the discrete element method. The results could provide guidance for gob-side entry retained with soft roof, floor, and seam in thin coal seams under similar geological conditions.

scholarly journals Study on the Characteristics of Top-Coal Caving and Optimization of Recovery Ratio in Steeply Inclined Residual High Sectional Coal Pillar

Geofluids ◽  
2020 ◽  
Vol 2020 ◽  
pp. 1-10
Author(s):  
Wenhua Yang ◽  
Xingping Lai ◽  
Pengfei Shan ◽  
Feng Cui ◽  
Yiran Yang
Keyword(s):  
Bulk Density ◽  
Coal Pillar ◽  
Engineering Practice ◽  
Recovery Ratio ◽  
Coal Seams ◽  
Balance System ◽  
Coal Recovery ◽  
Working Face ◽  
Coal Rock ◽  
Arch Structure

This paper is aimed at solving the technical problems such as low recovery ratio and frequent disasters in steeply inclined and extrathick coal seams at residual high sectional coal pillar. It takes the Wudong Coal Mine as an engineering background, a typical mine of steeply inclined and extrathick coal seams; the structural features of the top-coal caving at the steeply inclined residual high sectional coal pillar were analyzed using methods such as field monitoring and numerical simulation; a mechanical model of the top-coal arch structure was constructed, and the calculation method of top-coal caving height and related influencing factors was obtained. The results showed that the top-coal caving in the steeply inclined residual high sectional coal pillar was characterized as arch. Due to the existence of arch structure, the smooth caving of the top coal was hindered, resulting in a low top-coal recovery ratio, low support pressure at the working face, and differences detected by borehole television on the distribution of the top-coal cracks. With the advancement of the working face, the top-coal arch structure was in the process of dynamic evolution, as the old arch balance system was continuously replaced by the new arch balance system, and it continuously moved towards the upper top coal. The top-coal caving height was affected by factors such as length of the working face, bulk density of overlying coal rock, and cohesion of the top coal. The top-coal caving height increased with the length of the working face and the bulk density of the overlying coal rock mass but was inversely proportional to the cohesion of the top coal. Under the current mining conditions, the top-coal caving height was 39.8 m, which was much lower than the residual high sectional coal pillar height (71 m); the top coal cannot collapse completely. Based on the characteristics of the top-coal caving structure, the technology of sublevel advanced presplitting blasting was adopted to weaken the top coal in engineering practice, so that the top-coal caving structure moved up naturally. The daily coal production in the working face has increased by an average of 2419.6 tons, which has significantly improved the top-coal recovery ratio and production efficiency. The result provided a theoretical basis and application reference for similar residual high sectional coal pillar recovery.

Study on Pressure Observation of Fully Mechanized Caving Faces in Coal Seams with Rock Burst Danger in Xiagou Coal Mine

2014 ◽  
Vol 580-583 ◽  
pp. 1331-1334 ◽  
Author(s):  
Zhi Chao Tian ◽  
Ye Jiao Liu ◽  
Wen Cai Wang ◽  
Yu Hui Ren
Keyword(s):  
Rock Burst ◽  
Coal Mine ◽  
Practical Significance ◽  
Rock Stress ◽  
Coal Seams ◽  
Pressure Shock ◽  
Research Results ◽  
Roof Structure ◽  
Geological Conditions ◽  
Coal Rock

Taking the first fully mechanized caving face in Xiagou coal mine as research background, through the pressure observation on the scene field of fully mechanized caving face with rock burst danger, this essay reveals the pressure appearance law of coal seams rock burst danger and concludes that the field roof structure of fully roof mining is more conducive to the release of coal rock stress compared to layered mining structure and this method plays a mitigation role on moving pressure shock of coal rock. The fully mechanized caving faces can be explored fast under safety conditions. The research results are of great theoretical and practical significance to the mining production with similar geological conditions.

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