scholarly journals Height of the Fractured Zone in Coal Mining under Extra-Thick Coal Seam Geological Conditions

2021 ◽  
Vol 2021 ◽  
pp. 1-9
Author(s):  
Dequan Sun ◽  
Xiaoyan Li ◽  
Zhijie Zhu ◽  
Yang Li ◽  
Fang Cui
Keyword(s):  
Coal Seam ◽  
Coal Mining ◽  
Process Analysis ◽  
Failure Process ◽  
Analysis Method ◽  
Coal Seams ◽  
Fractured Zone ◽  
Seam Mining ◽  
Borehole Televiewer ◽  
Overlying Strata

The height of the fractured zone caused by coal mining is extremely significant for safely mining under water, water conservation, and gas treatment. At present, the common prediction methods of overburden fractured zone height are only applicable to thin and medium-thick coal seams, not suitable for thick and extra-thick coal seams. In order to determine the overburden fractured zone distribution characteristics of extra-thick seam mining, failure process analysis method of overlying strata was proposed based on key strata theory. This method was applied to 15 m coal seam of Tongxin coal mine, and fractured zone height was determined to be 174 m for 8100 panel. EH4 electromagnetic image system and borehole televiewer survey were also conducted to verify the theory results. The distribution of the electrical conductivity showed that the failure height was 150–170 m. Observation through the borehole televiewer showed that the fractured zone height was 171 m. The results of the two field test methods showed that the fractured zone height was 150–171 m, and it was consistent with the theory calculation results. Therefore, this failure process analysis method of overlying strata can be safely used for other coal mines.

scholarly journals A Mechanical Model of the Overlying Rock Masses in Undersea Coal Mining and a Stress-Seepage Coupling Numerical Simulation

2018 ◽  
Vol 2018 ◽  
pp. 1-14 ◽  
Author(s):  
Jie Fang ◽  
Lei Tian ◽  
Yanyan Cai ◽  
Zhiguo Cao ◽  
Jinhao Wen ◽  
...  
Keyword(s):  
Numerical Simulation ◽  
Coal Seam ◽  
Coal Mining ◽  
Water Inrush ◽  
Mining Area ◽  
Analysis Model ◽  
Fractured Zones ◽  
Working Face ◽  
Seam Mining ◽  
Overlying Strata

The water inrush of a working face is the main hidden danger to the safe mining of underwater coal seams. It is known that the development of water-flowing fractured zones in overlying strata is the basic path which causes water inrushes in working faces. In the engineering background of the underwater mining in the Longkou Mining Area, the analysis model and judgment method of crack propagation were created on the basis of the Mohr–Coulomb criterion. Fish language was used to couple the extension model into the FLAC3d software, in order to simulate the mining process of the underwater coal seam, as well as to analyze the initiation evolutionary characteristics and seepage laws of the fractured zones in the overlying strata during the advancing processes of the working face. The results showed that, during the coal seam mining process, the mining fractured zones which had been caused by the compression-shear and tension-shear were mainly concentrated in the overlying strata of the working face. Also, the open-off cut and mining working face were the key sections of the water inrush in the rock mass. The condition of the water disaster was the formation of a water inrush channel. The possible water inrush channels in underwater coal mining are mainly composed of water-flowing fractured zones which are formed during the excavation processes. The numerical simulation results were validated through the practical engineering of field observations on the height of water-flowing fractured zone, which displayed a favorable adaptability.

scholarly journals Influence of Valleys Terrain on Pressure of Fully Mechanized Working Faces in Shallow Coal Seams

2021 ◽  
Vol 2021 ◽  
pp. 1-11
Author(s):  
YingJie Liu ◽  
Qingjie Qi ◽  
Anhu Wang
Keyword(s):  
Coal Seam ◽  
Coal Mining ◽  
Rock Fracture ◽  
Mine Pressure ◽  
Overburden Rock ◽  
Coal Seams ◽  
Valley Bottom ◽  
Key Stratum ◽  
Seam Mining ◽  
The Impact

The absence of a key stratum during overburden rock movement is crucial to the mining pressure of fully mechanized coal mining faces. Using physical and numerical simulations, the 21304 mechanized mining in Daliuta and Huojitu coal mining faces 1−2 appeared twice during a pressure frame accident analysis. The results indicate that a lack of key overlying strata is crucial to the mining of lower coal seams, particularly for the upper sections of a single key stratum of coal. When the key stratum of the upper coal seam is absent, a stable masonry structure is formed after mining. It is easy to form stable stacked strata at the bottom of a coal seam. When developing gullies in deep terrains, the formation of the key stratum will be an upper rock fracture affected by the impact, resulting in a partial absence of the key stratum. When the key stratum is absent, the mining of upslope working faces and the probability of dynamic strata pressure increase with the overburden on the working face and mining of downslope faces. The face mine pressure development laws on the upper and lower coal seam mining were similar, mainly manifesting as “slope section >valley bottom section >back slope section.”

Research on the Overlying Strata in Full-Mechanized Coal Mining of Datong Jurassic Coal Multi-Layer Goaf

2012 ◽  
Vol 616-618 ◽  
pp. 402-405 ◽  
Author(s):  
Hong Chun Xia ◽  
Guo Sheng Gao ◽  
Bin Yu
Keyword(s):  
Coal Seam ◽  
Coal Mining ◽  
Coal Pillar ◽  
Mining Area ◽  
Mechanics Model ◽  
Roof Structure ◽  
Geological Conditions ◽  
Seam Mining ◽  
The Impact ◽  
Overlying Strata

According to the specific geological conditions in themulti-layer worked-out areas of Yongding coal seam, by the methods of integration of theoretic analysis, numerical value calculation and so on, we studied movement law of Overlaying Strata and influence of coal pillar in Coal seam mining, obtained the basic law of the overlying strata movement in multiplayer, provides a theoretical basis for the safe and efficient exploitation of the success of multiplayer. Many mining area in China is mining of closed distance coal seam group, By the impact of coal seam in the overlying, face and the tunnel roof structure will be different injury in sub-coal seam mining, Roof structure has changed greatly, even damage and easily take the roof leakage, When the the goaf communication with the overlying coal seams, caused by the induced secondary disasters such as face air leakage, Therefore, exploitation of the law of motion of the overlying strata in the multiplayer is a pressing problem. Exploitation multiplayer seam few theoretical and technical foundation at home and abroad, affecting the validity of the mining, rationality. although a lot of research on theory and technology of coal mining over the years[1~5], But it was not able to an overall comprehensive analysis of upper goaf adjacent goaf and overlying the coal pillar and present mining face, create a dynamic structural mechanics model, which is likely to cause the occurrence of disasters.

Prediction of Groundwater Inrush into Coal Mines from Aquifers Overlying the First Coal Seam in Eastern Ningxia Coalfield, China

2014 ◽  
Vol 1073-1076 ◽  
pp. 1634-1640
Author(s):  
En Ke Hou ◽  
Jie Feng ◽  
Fan Yang ◽  
Yan Jing Zhang
Keyword(s):  
Coal Seam ◽  
Coal Mining ◽  
Water Flow ◽  
Mining Area ◽  
Observation Data ◽  
Groundwater Inrush ◽  
Fractured Zone ◽  
Mining Areas ◽  
Seam Mining ◽  
Runoff Discharge

In the region where Eastern Ningxia coalfield locates, with the fragile eco-environment and the relative short water resources, it is significant to make clear the influence of coal mining on the groundwater in this region. According to analyses of water-filling factors for the 21 mine fields in the 7 mining areas and 1 independent mine field of Eastern Ningxia coalfield. Firstly, this paper selects the formula in the regulations on the preserving of the coal pillar and coal mining under buildings, water, rail and main shafts (regulations for short) and the Standard on the Exploration of Hydrogeology and Engineering-Geology in the Mining Area (GB12719-91) (standard for short) to calculate the height of water-flow fractured zone in the first coal seam mining, and compares the analysis results of the above formula to the observation data of 3 working faces, and determine the estimated method on the height of water-flow fractured zone, and then use “three maps-two predictions” method to complete the criterion of aquifer water-enrichment and inbreak in safety of the first coal seam. Finally, analyzing the influence of coal mining on the direction of groundwater and recharge-runoff-discharge conditions, the final comprehensive division program on the risk of the groundwater inrush is presented. The research results served as the general guidelines for the mine operations.

scholarly journals Control of the Internal and External Staggered Distance of Coal Mining Face to the Water-Conducting Fissures in the Overlying Strata of the Near Coal

2021 ◽  
Vol 2021 ◽  
pp. 1-12
Author(s):  
Zhiyuan Jin ◽  
Tao Peng
Keyword(s):  
Coal Seam ◽  
Coal Mining ◽  
Coal Mine ◽  
Calculation Formula ◽  
Coal Seams ◽  
Coal Face ◽  
Geological Conditions ◽  
Mining Face ◽  
Seam Mining ◽  
Water Proof

In Northwest China, rainfall is low, water resources are scarce, and the ecological environment is fragile. For shallow-buried and close-spaced coal seams with a thickness of upper coal bed >60∼70 m, the water-conducting fissures of the overlying rock will not penetrate the water-isolating layer after the upper coal seam is mined; the internal and external gap angles of the water-conducting fissures are not generated from the water-isolating layer. We set out to explore the critical internal and external dislocations for the second significant development of water-conducting fissures in the overlying rock after coal mining under control. A calculation model for the critical internal and external staggered distances of coal mining face in shallow-buried and close-spaced coal seams is established, the calculation formula is given, and the calculation formula for the critical seam mining ratio under the condition of internal staggered mining mode is given. Numerical simulation performed by UDEC methods: taking the overburden strata in the shallow-buried and close-spaced coal seam mining area of Shigetai Coal Mine as a prototype, it was verified that the critical internal and external offsets of the coal mining face in shallow-buried and close-spaced coal seams have a significant effect on the overlying water flow cracks in the mining of the lower coal seam. For the feasibility of developmental control, according to the engineering geological conditions of Shigetai, through the calculation method of external staggered distance, it is concluded that the distance of the open cut of the lower coal face and the upper coal face is only 21∼27 m, which is much smaller than the water barrier. It does not produce the critical distance of the water-conducting cracks. Therefore, in the process of mining the lower coal seam, the water-proof layer will produce water-conducting cracks, lose its water-proof performance, and cause water loss. This is also the cause of the water inrush accident in Shigetai Coal Mine.

The Seepage Risk Analysis of Surface Runoff Caused by the Shallow Thick Coal Seam Mining

2012 ◽  
Vol 170-173 ◽  
pp. 1353-1358
Author(s):  
Shun Feng Zhang ◽  
Rui Lin Hu ◽  
Xiong Wu
Keyword(s):  
Coal Seam ◽  
Surface Runoff ◽  
Ground Deformation ◽  
Ground Subsidence ◽  
Water Drainage ◽  
Thick Coal Seam ◽  
Mine Area ◽  
Fractured Zone ◽  
Seam Mining ◽  
Overlying Strata

As for shallow thick coal seam, the overlying strata can not form steady structure and will break down until reach the surface ground, which will induced large ground deformation and fractures in the overlying strata during the mining. Under the condition of strong rainfall, surface runoff will influx to the collapse pit or supply to other aquifers, and inrush into the roadway through water flowing fractured zone. This paper takes the 4201、4301、4302、4303 and 4401 coal faces of JingDong mine area in PingShuo for example, predicts the range of ground subsidence、settlement and the height of water flowing fractured zone dynamically after coal face mining, with the Flac3D numerical modeling software. On the base of result above and combined with geomorphic characteristics and hydrologic geology of the mine area, the author analyses risk of surface runoff seepage and put forward a dynamic water drainage design to prevent mine water bursting, which offers scientific foundation and data for safety production of the mine .

Distribution of Underground Pressure Law and Fracture Zone Prediction Research of Overburden in Steep and Multiple Coal Seams Mining

2013 ◽  
Vol 448-453 ◽  
pp. 3888-3892
Author(s):  
Ke Min Wei ◽  
Mao Sen Zhao ◽  
Ze Kang Wen ◽  
You Ling Fang
Keyword(s):  
Stress Concentration ◽  
Coal Mining ◽  
Fracture Zone ◽  
Coal Pillar ◽  
Steep Seam ◽  
Coal Seams ◽  
Level 1 ◽  
Mining Work ◽  
Seam Mining ◽  
Protection Pillar

Use Taiping coal mines second horizontal (+1100m~+900 m level ) 1#, 3# and 5# coal seam in Panzhihua Baoding as the research object, apply the problem solving nonlinear large deformation finite difference method (FLAC), to research the steep multi-seam mining of pressure distribution and characteristics of fracture zone. The results show that: (1)During the course of three coal mining extraction, the stress of goaf surrounding rocks will be changed. (2)When the nearby coal is mining, the coal pillar come into being stress concentration near the area. when the mining work continues, the goaf will have an effect on the protection pillar, which is similar to the "liberate". the effect of coal pillar and stress concentration nearby will be eased; (3)After the coal mining, plastic failure has occurred over the protection pillar, forming a water guide channel. Research results can be as a reference for similar steep seam mining.

scholarly journals The Key Stratum Structure Morphology of Longwall Mechanized Top Coal Caving Mining in Extra-Thick Coal Seams: A Typical Case Study

2020 ◽  
Vol 2020 ◽  
pp. 1-13 ◽  
Author(s):  
Fulian He ◽  
Xiaobin Li ◽  
Wenrui He ◽  
Yongqiang Zhao ◽  
Zhuhe Xu ◽  
...  
Keyword(s):  
Coal Seam ◽  
Cantilever Beam ◽  
Coal Seams ◽  
Key Strata ◽  
Key Stratum ◽  
Structure Morphology ◽  
Coal Wall ◽  
Coal Seam Thickness ◽  
Longitudinal Cracks ◽  
Overlying Strata

Longwall mechanized top coal caving mining (LMTCCM) in extra-thick coal seams has its own characteristics. The law of mining pressure and overlying strata failure height in extra-thick coal seams are much larger than those of medium-thick and thick coal seams. The key stratum structure morphology also has an important influence on the law of overlying strata movement and stability of surrounding rock. Based on the engineering geological conditions, this paper used the method of theoretical analysis and numerical simulation to study the key stratum structure morphology of LMTCCM in extra-thick coal seams. The results show that under the condition of LMTCCM in extra-thick coal seams, the key stratum forms the structure of low cantilever beam and high hinged rock beam. With the increase of coal seam thickness, the breaking position of cantilever beam is closer to the coal wall. Through theoretical calculation, it is obtained that the breaking length of cantilever beam is 31.5 m and the breaking position of cantilever beam is 15.4 m away from coal wall. With the increase of cycle, key strata will undergo the evolution law from the generation of longitudinal cracks to the hinged structure and then to the cantilever beam structure. The breakage of key strata will cause the expansion of longitudinal cracks and the overall synchronous movement of overlying strata. With the increase of coal seam thickness, the distribution of longitudinal cracks will gradually transfer from the upper part of goaf to the deep part of coal body in space and increase in quantity. This research is of great significance for improving the stability of overlying strata and ensuring the safe and efficient mining of extra-thick coal seams.

scholarly journals Failure Mechanism and Control Technology of Thick and Soft Coal Fully Mechanized Caving Roadway under Double Gobs in Close Coal Seams

2020 ◽  
Vol 2020 ◽  
pp. 1-23
Author(s):  
Shengrong Xie ◽  
Xiaoyu Wu ◽  
Dongdong Chen ◽  
Yaohui Sun ◽  
En Wang ◽  
...  
Keyword(s):  
Numerical Simulation ◽  
Coal Seam ◽  
Field Distribution ◽  
Control Technology ◽  
Coal Seams ◽  
Anchor Bolt ◽  
Anchor Cable ◽  
Coal Pillars ◽  
Seam Mining ◽  
And Control

The surrounding rock of the roadway under double gobs in the lower coal seams is partially damaged by the mining of the upper coal seam and the stress superimposition of the stepped coal pillars. What is worse, the upper layer of the roof is collapse gangue in double gobs, which makes the anchor cable unable to anchor the reliable bearing layer, so the anchoring performance is weakened. The actual drawing forces of the anchor bolt and anchor cable are only approximately 50 kN and 80 kN, respectively. The roadway develops cracks and large deformations with increasing difficulty in achieving safe ventilation. In view of the above problems, taking the close coal seam mining in the Zhengwen Coal Mine as the engineering background, a theoretical calculation is used to obtain the loading of the step coal pillars and the slip line field distribution of the floor depth. The numerical simulation monitors the stress superimposition of stepped coal pillars and the distribution of elastoplastic areas to effectively evaluate the layout of mining roadways. The numerical simulation also analyzes the effective prestress field distribution of the broken roof and grouting roof anchor cable. A laboratory test was used to monitor the strength of the grouting test block of the broken coal body. Then, we proposed that grouting anchor cable be used to strengthen the weak surface of the roof and block the roof cracks. From on-site measurement, the roadway was seen to be arranged in the lateral stress stabilization area of the stepped coal pillars, the combined support technology of the grouting anchor cable (bolt) + U type steel + a single prop was adopted, the roadway deformation was small, the gas influx was reduced, and the drawing force of the anchor bolt and the anchor cable was increased to approximately 160 kN and 350 kN, respectively. The overall design and control technology of the roadway can meet the site safety and efficient production requirements.

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