Study on Failure of Soft Overburden of Fully Mechanized Top Coal Caving

2012 ◽  
Vol 446-449 ◽  
pp. 2192-2195
Author(s):  
Jin Shan Wang ◽  
Zhong Chang Wang
Keyword(s):  
Abutment Pressure ◽  
Main Roof ◽  
Material Model ◽  
Stress And Strain ◽  
Similar Material ◽  
Coal Face ◽  
Coal Wall ◽  
Internal Stress Field ◽  
Seam Mining ◽  
Step Distance

The similar material model experiment takes the NO.S2S9 coal face in DaPing coal mine as a prototype to research the characteristics of movement and failure of the soft overburden under fully mechanized top coal caving conditions. The abutment pressure distribution and periodic weighting, caving span are given by monitoring the stress and strain in the similar material model. The results show that rocks fracture extended from button with the advance of workface. The first caving step distance of main roof is 34m. The periodic caving step distance of main roof is 10m. The internal stress field is 10m and the peak abutment pressure point is 80m far away from the coal wall, while the disturbance range in anterior coal wall is 200m. Some cracks are closed in the later stage. The advance of around 300m is the distance that the water flowing fractured zone’s height reaches the highest value. The biggest height of water- flowing fractured zone is 140m. The soft overburden has strong plastic deformation capability. The synchronism of failure and movement of overburden is strong. The failured overburden is compacted and the cracks keep close with the advance of workface. The simulation experiment provides a reference bases for the application and promotion of thick seam mining technology.

Study on Movement Law of Overlying Strata during Shallow Thinner Seam Mining in Shendong Mining Area

2011 ◽  
Vol 361-363 ◽  
pp. 188-192
Author(s):  
Xi Cheng Zhang ◽  
Zhong Cheng Qin ◽  
Qing Hai Li ◽  
Ning Zhang
Keyword(s):  
Abutment Pressure ◽  
Initial Pressure ◽  
Mining Area ◽  
Shell Morphology ◽  
Coal Face ◽  
Pressure Step ◽  
Powered Support ◽  
Seam Mining ◽  
First Time ◽  
Overlying Strata

Given the particularity and the first time for shallow thinner seam mining in Shendong mining area, the overlying strata movement law during shallow thinner coal seam mining has been studied in this paper based on the fully mechanized thinner coal face of NO.71301 in Shi Getai coal mine, resorting to observation on spot, numerical simulation and other methods. Through research, the important laws and features had been obtained, such as, initial pressure step, periodical pressure step, the obvious partition of periodical weighting, the unitary elasticity distribution of front abutment pressure, and the stress shell morphology over the mining rock, which provides important characteristic for roof control and foundation for the powered support selection.

Experimental Investigation of Simulating Similar Materials of Multi-Seam Mining in Steep

2011 ◽  
Vol 255-260 ◽  
pp. 3765-3769
Author(s):  
Kui Xing Liu ◽  
Xiao Gang Wei ◽  
Shu Xian Liu ◽  
Li Ping Lv
Keyword(s):  
Similarity Index ◽  
Physical And Mechanical Properties ◽  
Material Model ◽  
Prototype Model ◽  
Similar Material ◽  
Initial State ◽  
Deformation And Failure ◽  
Model Method ◽  
Movement And Deformation ◽  
Seam Mining

The similar material model method is used to simulate to the movement of cover rock and ground which is caused by mining underground coal, the substance of deformation and failure law of similar material model method is that artificial materials which are used in the experiment have similar physical and mechanical properties as archetype, affinity constants of geometry, movement and force are used as similarity index and criteria in the simulation experiment as the most important factors. The prototype model is made into a certain proportion model in reduction, and the initial state and boundary conditions of model must be similar as archetype. Then exploit the simulating model, the regular patterns of fault destruction, curve, movement and deformation of cover rock can be discovered in the process of exploiting the simulating model, and the movement and deformation of the surface and its sphere of influence can also be got. Finally the observations of model can be calculated and projections up to the prototype by the similarity index, so the most important regular pattern of the prototype can be got.

The Change Regularity of Abutment Pressure under Various Propulsive Distance in Coal Face

2012 ◽  
Vol 524-527 ◽  
pp. 769-775
Author(s):  
Jin Dai ◽  
Xin Jie Liu
Keyword(s):  
High Pressure ◽  
Rock Pressure ◽  
Concentration Factor ◽  
Abutment Pressure ◽  
Main Roof ◽  
Low Pressure ◽  
Coal Face ◽  
Change Trend ◽  
Stability Area

The application of UDEC software helps to simulate the changing regularity of the front and posterior abutment pressure and the pressure in the goaf within the scope of propulsive distance 220m in the coal face. Incorporating the Origin software the simulation analyzed the changes and correlation of the three kinds of pressure. We can see that when the propulsive distance is within 60m the change of the front and pressure is the same to the change of the back abutment and with the increasing of the pressure the posterior abutment pressure reaches its peak first. When the propulsive distance exceeds 60m the pressure of caving gangue in the goaf begins to increase and share some of abutment pressure. Each time the main roof collapses the concentration factor and the location of the peak of the front abutment pressure will fluctuate. The concentration factor fluctuates between 2.04~2.41 and the location of peak fluctuate between 7m to 10m. With the propulsive distance increasing, the posterior abutment pressure will tend towards stability when the propulsive distance is 140 m. The goaf which experiences the change trend of low pressure -high pressure -reducing to raw rock pressure has three areas: depressor area, pressurization area and stability area. The stress depressor area which is in the range of 10 to 20 m exists every 20 to 30m in the cut-hole and the gangue compacting area.

Effective Filling Rate in Filling Mining’s Influence on Overlying Strata’s Movement

2013 ◽  
Vol 734-737 ◽  
pp. 741-745
Author(s):  
Jian Hao ◽  
Yong Kui Shi ◽  
Min Hua Qi ◽  
Lei Zhang
Keyword(s):  
Abutment Pressure ◽  
Main Roof ◽  
Pressure Control ◽  
Mine Pressure ◽  
Pressure Curve ◽  
Filling Rate ◽  
A Value ◽  
Admissible Condition ◽  
Coal Wall ◽  
Supporting Degree

Similarities and differences of overlying strata movement rule and abutment pressure distribution between filling stope and traditional strope was analysied guided by “practical mine pressure control theory ”. The admissible condition of strata’s depending from bending failure to caving was put forward, and caving zone’s height was analysied on the basis of this. Results showed that caving zone’s height and resistant force required by hydraulic pillar would decrease leapingly ,until the lowest strata transfer into the main roof, and when pressure was stable main roof’s maximum subsidence would become smaller. With the increase of the effective filling rate, filling body’s supporting degree to overlying would increase, when the filling rate reaches to a value, Coal wall’s edge would not appear the plastic zone, the abutment pressure curve is monotone decline with the peak near coal wall edge .

Relationship between Methane Emission and Strata Behavior at Island Coal Face

2012 ◽  
Vol 524-527 ◽  
pp. 662-667
Author(s):  
Xin Xian Zhai ◽  
Fu Lin Wang
Keyword(s):  
Coal Mine ◽  
Methane Emission ◽  
Emission Rate ◽  
Main Roof ◽  
Control Measures ◽  
Emission Rates ◽  
Coal Face ◽  
Coal Wall ◽  
Strata Behavior ◽  
Methane Emission Rate

According to the practical conditions of the island coal face in No.2 Coal Mine of Pingdingshan Coal Company Ltd., China, the strata behaviors and methane emission were monitored and their two relationships were analyzed. The results indicate that strata behavior at coal face affects its methane emission rates at coal wall and goaf，which the quantity of methane emission rate at coal face is largely increasing after main roof weighting. So through the monitor of periodic roof weighting time, larger methane emission rate at coal face can be predicted. Then the related methane control measures can be taken timely.

scholarly journals Inorganic Cement Grouting for Reinforcing Triangular Zone of Highly Gassy Coal Face with Large Mining Height

Energies ◽  
2018 ◽  
Vol 11 (10) ◽  
pp. 2549 ◽  
Author(s):  
Bin Song ◽  
Shuai Zhang ◽  
Dongsheng Zhang ◽  
Gangwei Fan ◽  
Wei Yu ◽  
...  
Keyword(s):  
Abutment Pressure ◽  
Setting Time ◽  
Simulation Software ◽  
Coal Face ◽  
Cement Grouting ◽  
Geological Conditions ◽  
Fracture Development ◽  
Coal Wall ◽  
Grouting Reinforcement ◽  
Triangular Zone

Aiming to address the serious problem of coal wall spalling in the triangular zone of the coal face end under high-intensity mining, this paper introduces inorganic cement grouting reinforcement technology for medium-depth holes based on the specific geological conditions of the Sihe coal mine in China. Firstly, the effects of different water-to-material ratios and various accelerators on setting time and uniaxial compressive strength (UCS) of grouting materials and consolidation coal are studied. The results show that the combination of 2% accelerator I, 0.3% accelerator II, and 3.0% accelerator III was the most effective. Then, FLAC3D numerical simulation software was used to analyze the distribution laws of the plastic zone, the lateral abutment pressure, and abutment stresses in the face ends during repeated mining. The results indicate that the zone within 25–65 m of the front of the coal face was initially affected by the front abutment pressure. In this area, the stress value decreased slowly and fracture development was relatively intense. Grouting with high pressure and a large flow rate should be used in this scenario as the industrial experiment results indicated that the proposed inorganic cement grouting reinforcement technology could effectively control coal wall spalling and provide technical support for safe and efficient mining.

scholarly journals Water Inrush and Failure Characteristics of Coal Seam Floor Over A Confined Aquifer

2021 ◽  
Author(s):  
Min Cao ◽  
Shangxian Yin ◽  
Bin Xu
Keyword(s):  
Coal Seam ◽  
Abutment Pressure ◽  
Water Pressure ◽  
Shear Stresses ◽  
Confined Aquifer ◽  
Working Face ◽  
Stress Coefficient ◽  
Coal Wall ◽  
Failure Depth ◽  
Seam Mining

Abstract Failure behaviors of the floor rocks under coal seam mining in the conditions of hard magma rock roof and confined aquifer are studied. Based on the theory of rock stresses and elasticity mechanics, the combined effects of the abutment pressure induced by the hard roof and by the water pressure under the thin aquicludes of the floor rocks were considered, and a mechanical model was constructed along the strike of the working face. An analytical solution of stress distribution was derived in the floor rocks, the distributions of vertical, horizontal and shear stresses were calculated. In combination with the in-situ measurement, the results show that: 1) when the periodic pressure caused by the roof collapse occurs on the working face, and the maximum stress concentration in the floor appears at the elastic-plastic junction in the direction of the strike of the working face. With the increase of the depth of the floor, the horizontal stress coefficient tends to decrease, and the corresponding shear stress coefficient isoline shows a “symmetric spiral” distribution and propagates downward to the floor at a certain angle with the vertical direction. This causes the floor rocks to generate compression and shear or tension and shear failure. 2) when the immediate roof of coal seam is the magma rock, the abutment pressure shows a trend of a slow increase initially and then a rapid increase later. The peak value of abutment pressure appears at the location of 4 - 6 meters from the coal wall of the working face, and the concentration coefficient of the abutment pressure is between 1.4 and 1.8. 3) according to the measurement and calculation of the failure depths of the floor at different positions under the same coal seam, it is found that the maximum failure depth appears near the coal wall of the working face. The failure depth reduces by 11.6% after the floor goes through “the roof caving and re-compaction”, which causes the fractures in the floor to close and the thickness of the effective aquiclude increases. In the un-mined area of the working face, the failure depth is 55% of the maximum failure depth. 4) both the theoretical calculation and the numerical simulation show that the failure depth of the floor increases obviously under the combined action of high vertical stress and the water pressure. Under the condition that the thickness of the aquiclude is relatively thin, the water pressure of the floor and pressure intensity of the roof are the sensitive factors to affect the maximum failure depth of the floor.

Reasonable Entry Layout of Lower Seam in Multi-Seam Mining Based on Numerical Simulation

2013 ◽  
Vol 295-298 ◽  
pp. 2980-2984
Author(s):  
Xiang Qian Wang ◽  
Da Fa Yin ◽  
Zhao Ning Gao ◽  
Qi Feng Zhao
Keyword(s):  
Numerical Simulation ◽  
Stress Distribution ◽  
Coal Seam ◽  
Coal Mine ◽  
Abutment Pressure ◽  
Surrounding Rock ◽  
Geological Conditions ◽  
Seam Mining

Based on the geological conditions of 6# coal seam and 8# coal seam in Xieqiao Coal Mine, to determine reasonable entry layout of lower seam in multi-seam mining, alternate internal entry layout, alternate exterior entry layout and overlapping entry layout were put forward and simulated by FLAC3D. Then stress distribution and displacement characteristics of surrounding rock were analyzed in the three ways of entry layout, leading to the conclusion that alternate internal entry layout is a better choice for multi-seam mining, for which makes the entry located in stress reduce zone and reduces the influence of abutment pressure of upper coal seam mining to a certain extent,. And the mining practice of Xieqiao Coal Mine tested the results, which will offer a beneficial reference for entry layout with similar geological conditions in multi-seam mining.

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

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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