scholarly journals Stress and deformation analysis of gob-side pre-backfill driving procedure of longwall mining: a case study

2021 ◽  
Author(s):  
Rui Wu ◽  
Penghui Zhang ◽  
Pinnaduwa H. S. W. Kulatilake ◽  
Hao Luo ◽  
Qingyuan He
Keyword(s):  
Rock Mass ◽  
Stress Distribution ◽  
Coal Seam ◽  
Abutment Pressure ◽  
Longwall Mining ◽  
Vertical Stress ◽  
Floor Level ◽  
Working Face ◽  
Floor Heave ◽  
Stress And Deformation

AbstractAt present, non-pillar entry protection in longwall mining is mainly achieved through either the gob-side entry retaining (GER) procedure or the gob-side entry driving (GED) procedure. The GER procedure leads to difficulties in maintaining the roadway in mining both the previous and current panels. A narrow coal pillar about 5–7 m must be left in the GED procedure; therefore, it causes permanent loss of some coal. The gob-side pre-backfill driving (GPD) procedure effectively removes the wasting of coal resources that exists in the GED procedure and finds an alternative way to handle the roadway maintenance problem that exists in the GER procedure. The FLAC3D software was used to numerically investigate the stress and deformation distributions and failure of the rock mass surrounding the previous and current panel roadways during each stage of the GPD procedure which requires "twice excavation and mining". The results show that the stress distribution is slightly asymmetric around the previous panel roadway after the “primary excavation”. The stronger and stiffer backfill compared to the coal turned out to be the main bearing body of the previous panel roadway during the "primary mining". The highest vertical stresses of 32.6 and 23.1 MPa, compared to the in-situ stress of 10.5 MPa, appeared in the backfill wall and coal seam, respectively. After the "primary mining", the peak vertical stress under the coal seam at the floor level was slightly higher (18.1 MPa) than that under the backfill (17.8 MPa). After the "secondary excavation", the peak vertical stress under the coal seam at the floor level was slightly lower (18.7 MPa) than that under the backfill (19.8 MPa); the maximum floor heave and maximum roof sag of the current panel roadway were 252.9 and 322.1 mm, respectively. During the "secondary mining", the stress distribution in the rock mass surrounding the current panel roadway was mainly affected by the superposition of the front abutment pressure from the current panel and the side abutment pressure from the previous panel. The floor heave of the current panel roadway reached a maximum of 321.8 mm at 5 m ahead of the working face; the roof sag increased to 828.4 mm at the working face. The peak abutment pressure appeared alternately in the backfill and the coal seam during the whole procedure of "twice excavation and mining" of the GPD procedure. The backfill provided strong bearing capacity during all stages of the GPD procedure and exhibited reliable support for the roadway. The results provide scientific insight for engineering practice of the GPD procedure.

scholarly journals Stress Distribution in a Coal Seam before and after Bump Initiation

10.14311/260 ◽  
2001 ◽  
Vol 41 (4-5) ◽  
Author(s):  
J. Vacek
Keyword(s):  
Rock Mass ◽  
Stress Distribution ◽  
Coal Seam ◽  
Mathematical Modelling ◽  
Rock Burst ◽  
Open Space ◽  
Longwall Mining ◽  
Time Dependent ◽  
Deep Tunnel ◽  
Before And After

This paper deals with to the behaviour of open rock that occurs, for example, during longwall mining in coal mines, in deep tunnel, or shaft excavation.Longwall instability leads to extrusion of rock mass into an open space. This effect is mostly referred to as a bump, or a rock burst. For bumps to occur, the rock has to possess certain particular rock burst properties leading to accumulation of energy and the potential to release this energy. Such materials may be brittle, or the bumps may arise at the interfacial zones of two parts of the rock, that have principally different material properties.The solution is based on experimental and mathematical modelling. These two methods have to allow the problem to be studied on the basis of three presumptions: – the solution must be time dependent – the solution must allow the creation of crack in the rock mass – the solution must allow an extrusion of rock into an open space (bump effect)

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 Experimental and Numerical Study of Rock Stratum Movement Characteristics in Longwall Mining

2019 ◽  
Vol 2019 ◽  
pp. 1-15 ◽  
Author(s):  
Wan-rong Liu
Keyword(s):  
Stress Concentration ◽  
Coal Seam ◽  
Longwall Mining ◽  
Roof Rock ◽  
Numerical Study ◽  
High Stress ◽  
Engineering Practice ◽  
Rock Stratum ◽  
Working Face ◽  
Coal Wall

The roof fracture is the main cause of coal mine roof accidents. To analyze the law of movement and caving of the roof rock stratum, the roof subsidence displacement, rock stratum stress, and the rock stratum movement law were analyzed by using the methods of the particle discrete element and similar material simulation test. The results show that (1) as the working face advances, regular movement and subsidence appears in the roof rock strata, and the roof subsidence curve forms a typical “U” shape. As the coal seam continues to advance, the maximum subsidence displacement remains basically constant, and the subsidence displacement curves present an asymmetric flat-bottomed distribution. (2) After the coal seam is mined, the overburden forms an arched shape force chain, and the arched strong chain is the path of the overburden transmission force. The farther away from the coal seam, the smaller the stress concentration coefficient is, but it is still in a high stress area, and the stress concentration position moves toward the middle area of the goaf. The stress concentration in front of the coal wall is the source of force that forms the abutment pressure. (3) Above the coal wall towards the goaf, a stepped fracture was formed in the roof rock stratum. The periodic fracture of the rock stratum is the main cause of the periodic weighting of the working face. Understanding the laws of rock movement and stress distribution is of great significance for guiding engineering practice and preventing the roof accidents.

scholarly journals The effects of dynamic pressure on the stability of prepared drifts near the working surface areas

2021 ◽  
Vol 62 (1) ◽  
pp. 85-92
Author(s):  
Nhan Thi Pham ◽  
Nghia Viet Nguyen ◽  
Keyword(s):  
Rock Mass ◽  
Stress Distribution ◽  
Dynamic Pressure ◽  
Coal Pillar ◽  
Side Wall ◽  
Stability Loss ◽  
Surface Areas ◽  
Working Face ◽  
Deformation Stress ◽  
The Right

Due to the effects of dynamic pressure, the stress distribution of rock mass is very complex. The reason for this could be a risk of stability loss for an auxiliary tunnel system constructed within the study area. In this article by using Flac3D software the author simulated two adjacent working faces with the thickness of 5 m natural coal pillar. Three factors: the upper working face excavation process, auxiliary tunnel mining process, and the location of lower working face, affected by deformation, stress distribution, safety of lower floor area and surrounding rock mass of tunnel. The research results show that during the excavation, the mechanical behavior of the rock mass surrounding the auxiliary tunnel showed displacements, volatility, and phase characteristic. The displacement on the auxiliary tunnel boundary in both excavation and working face cases showed that the roof and the left side wall displacement was greater than the right side wall and the bottom. Therefore, the distance between the auxiliary tunnel and the empty mining space needs to be computed to meet technical and economic requirements.

scholarly journals Mining Stress Distribution and Fault-Slip Behavior: A Case Study of Fault-Influenced Longwall Coal Mining

Energies ◽  
2019 ◽  
Vol 12 (13) ◽  
pp. 2494 ◽  
Author(s):  
Peng Kong ◽  
Lishuai Jiang ◽  
Jiaming Shu ◽  
Lu Wang
Keyword(s):  
Shear Stress ◽  
Stress Distribution ◽  
Coal Seam ◽  
Normal Stress ◽  
Longwall Mining ◽  
Hanging Wall ◽  
Fault Slip ◽  
Lagrangian Analysis ◽  
Slip Mechanism ◽  
3 Dimensional

It is well accepted that faults have significant impacts on the safe production of underground coal mines; however, the fault-slip mechanism during longwall mining through a fault still needs to be investigated. In this study, the distribution of microseismicity events during panel mining through a fault is analyzed, and 3-dimensional fast Lagrangian analysis of continua was used to study the mining stress distribution and fault-slip behavior under the two different mining directions, i.e., mining the panel through the fault from the footwall, or mining the panel through the fault from the hanging wall. The research shows that when the panel is mined through the fault from the footwall, the shear displacement of the fault is significantly greater than those created by mining the panel through the fault from the hanging wall. Under the two mining directions, the variation behaviors of the normal stress and shear stress on the fault are quite different, and fault-slips mainly occur in fault areas where the normal stress decreases. When mining the panel through the fault from the footwall, the slip mainly occurs in the coal-seam roof fault, and when mining the panel through the fault from the hanging wall, the slip mainly occurs in the coal-seam floor fault. According to the variations in the normal stress and shear stress of the fault during the period of mining the panel through the fault, the mechanism of the fault slip can be divided into three categories. 1: Normal stress and shear stress decrease abruptly, but the reduction of the normal stress is greater than that of the shear stress. 2: The normal stress is continuously reduced, the shear strength of the fault is decreased, and the shear stress is suddenly increased. 3: Both the normal stress and the shear stress increase, but the increase in the shear stress is greater than that of the normal stress. These research results can provide a reference for the layout of panels and for fault-slip-induced disaster prevention under similar conditions.

Stress Shell Mechanical Mechanism of Fully-Mechanized Face Enhancing the Upper Limit for Coal Mining and Risk Analysis of Support Break-Off

2012 ◽  
Vol 524-527 ◽  
pp. 466-470
Author(s):  
Jun Ling Hou ◽  
Yan Sun
Keyword(s):  
Stress Distribution ◽  
Coal Seam ◽  
Coal Mining ◽  
Surrounding Rock ◽  
Mechanical Environment ◽  
Upper Limit ◽  
Working Face ◽  
Distribution Rule ◽  
Geological Conditions ◽  
Mining Face

Based on the geological conditions and specific mining technology conditions of the 11014 mining face of Panbei mine in HuaiNan mining group ,using the FLAC3D software, simulate the stress distribution rule and disruption field distribution rule of surrounding rock of Fully-Mechanized face enhancing the upper limit for coal mining along the tendency and trend of coal seam by different mining speed of 6 m/d, 4 m/d and 2 m/d. draw the conclusion that enhancing the mining speed can alleviate the pressure of the working face ,improve the working face mechanical environment,and reduce the extent of the failure field.It provides the theory basis and reference for Fully-Mechanized face enhancing the upper limit for coal mining under similar conditions.

The Research on Abutment Stress Distribution and Fracture Characteristics of Coal Seam in Longwall Face

2011 ◽  
Vol 361-363 ◽  
pp. 103-107
Author(s):  
Chuan Ming Li
Keyword(s):  
Stress Distribution ◽  
Coal Seam ◽  
Surrounding Rock ◽  
Geometrical Shape ◽  
Horizontal Distance ◽  
Site Testing ◽  
Fracture Characteristics ◽  
Working Face ◽  
Coal Wall ◽  
Overlying Strata

The abutment stress results from the load coming from overlying strata above the influence range of abutment stress and the load which coming from overlying strata above the stress shell passed by the shell. Through the mechanical calculation,this paper analyzed abutment stress distribution and fracture characteristics of coal seam resulted from the load of overlying strata passed by stress shell which exists in surrounding rock of working face, and obtained the laws of abutment stress distribution and fracture in coal seam in combination with numerical simulation and site testing. The characteristics of abutment stress distribution and fracture are related to the geometrical shape of the stress shell, such as height of the stress shell, horizontal distance between top of stress shell and coal wall,and width of stress shell skewback.

scholarly journals Analysis on Rock Burst Risks and Prevention of a 54 m-Wide Coal Pillar for Roadway Protection in a Fully Mechanized Top-Coal Caving Face

2021 ◽  
Vol 2021 ◽  
pp. 1-7
Author(s):  
Zhihua Li ◽  
Ke Yang ◽  
Jianshuai Ji ◽  
Biao Jiao ◽  
Xiaobing Tian
Keyword(s):  
Coal Seam ◽  
Rock Burst ◽  
Influencing Factors ◽  
Abutment Pressure ◽  
Large Diameter ◽  
Coal Pillar ◽  
Distribution Characteristics ◽  
Pressure Relief ◽  
Working Face ◽  
Coal Pillars

A case study based on the 401103 fully mechanized caving face in the Hujiahe Coal Mine was carried out in this research to analyze the rock burst risks in a 54 m-wide coal pillar for roadway protection. Influencing factors of rock burst risks on the working face were analyzed. Stress distribution characteristics on the working face of the wide coal pillar for roadway protection were discussed using FLAC3D numerical simulation software. Spatial distribution characteristics of historical impact events on the working face were also investigated using the microseismic monitoring method. Results show that mining depth, geological structure, outburst proneness of coal strata, roof strata structure, adjacent mining area, and mining influence of the current working face are the main influencing factors of rock burst on the working face. Owing to the collaborative effects of front abutment pressure of the working face and lateral abutment pressure in the goaf, the coal pillar is in the ultimate equilibrium state and microseismic events mainly concentrate in places surrounding the coal pillars. Hence, wide coal pillars become the regions with rock burst risks on the working face. The working face adopts some local prevention technologies, such as pressure relief through presplitting blasting in roof, pressure relief through large-diameter pores in coal seam, coal seam water injection, pressure relief through large-diameter pores at bottom corners, and pressure relief through blasting at bottom corners. Moreover, some regional prevention technologies were proposed for narrow coal pillar for roadway protection, including gob-side entry, layer mining, and fully mechanized top-coal caving face with premining top layer.

scholarly journals Study on Stress Distribution Law of High-Efficiency Paste Backfilling Working Face with Solid Waste in Thick Coal Seam

2020 ◽  
Vol 2020 ◽  
pp. 1-13
Author(s):  
Meng Zhang ◽  
Dan Fang
Keyword(s):  
Sustainable Development ◽  
Stress Distribution ◽  
Coal Seam ◽  
Solid Waste ◽  
Research Methods ◽  
High Efficiency ◽  
Distribution Law ◽  
Thick Coal Seam ◽  
The Sustainable Development ◽  
Working Face

The high-efficiency paste backfilling mining technology of solid waste in thick coal seam above 6 m is a complex system engineering, which involves mining, backfilling, supporting, subsidence, safety, and other aspects, so it is of great strategic significance to study the technology. In this paper, on the basis of comprehensive research methods such as laboratory experiments, theoretical analysis, computer programming, and other comprehensive research methods, aiming at the problems of low production capacity and high paste backfilling cost, taking the mining of No. 3 Coal Seam under buildings in Lu’an area as the research object, the stress distribution law of high-efficiency paste backfilling working face with solid waste in more than 6-meter-thick coal seam was carried out. The main achievements are as follows: On the basis of the theoretical establishment of the program method for the instability discriminant analysis of roof rock beam failure with the change of backfilling body unit strength with time, a numerical calculation model considering the change process of backfilling body strength is established. The stress distribution analysis of the E1302 working face before and during the mining process plays a guiding role in the actual production of the whole working face and roadway. The research results support the sustainable development of coal mining enterprises from technology, which has great economic, social, and environmental benefits, and can promote the industrialization of green mining high-tech in Shanxi Province and even the whole country and can promote the green mining technology progress of paste backfilling in coal mines in China, which is of great significance to the sustainable development of mining production and environmental construction.

scholarly journals Stability of "Support-Surrounding Rock" System for Fully Mechanized Longwall Mining in Steeply Dipping Coal Seams

2021 ◽  
Author(s):  
Luo Shenghu ◽  
tong wang ◽  
Wu Yongping ◽  
Huangfu Jingyu ◽  
Zhao Huatao
Keyword(s):  
Coal Seam ◽  
Longwall Mining ◽  
Stability Control ◽  
Surrounding Rock ◽  
Coal Seams ◽  
Physical Test ◽  
Rock System ◽  
Working Face ◽  
The Stability ◽  
Mining Height

Abstract The key to the safe and efficient longwall mining of steeply dipping seams lies in the stability control of the "support-surrounding rock" system. This paper analyzes the difficulty of controlling the stability of the support during the longwall mining process of steeply dipping coal seams in terms of the characteristics of the non-uniform filled-in gob using a combination of physical test, theoretical analysis and field measurements. Considering the floor as an elastic foundation, we built a "support-surrounding rock" mechanical model based on data obtained on "support-surrounding rock" systems in different regions and the laws of support motion under different load conditions. Our findings are summarized as follows. First, depending on the angle of the coal seam, the caving gangue will roll (slide) downward along the incline, resulting in the formation of a non-uniform filling zone in the deep gob in which the lower, middle, and upper sections are filled, half-filled, and empty, respectively. In addition, an inverted triangular hollow surface is formed on the floor of the gob in the middle and upper sections behind the support. Furthermore, as the angle of the coal seam, length of the working face, and mining height increase, the characteristics of the non-uniform filled-in gob are enhanced. Second, we found that, as a result of support by the gangue, the "support-surrounding rock" system is relatively stable in the lower part of the working face while, in the middle and upper sections of the working face, the contact method and loading characteristics of the support are more complicated, making stability control difficult. Third, the magnitude and direction of the load, action point, and mining height all affect the stability of the support to varying degrees, with the tangential load and action position of the roof load having the most significant impacts on the stability of the support. Under loading by the roof, rotation and subsidence of the support inevitably occur, with gradually increasing amplitude and effects on the inter-support and sliding forces. Finally, we found that it is advisable in the process of moving the support to adopt "sliding advance of support" measures and to apply a "down-up" removal order to ensure overall stability. These research results provide reference and guidance of significance to field practice production.

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