Research on Reasonable Position of Roadway for close Multi-Seam and its Application

2013 ◽  
Vol 807-809 ◽  
pp. 2393-2397
Author(s):  
Ai Qing Liu
Keyword(s):  
Stress Concentration ◽  
Coal Seam ◽  
Abutment Pressure ◽  
Dynamic Pressure ◽  
Coal Pillar ◽  
Stress Zone ◽  
Concentration Degree ◽  
Residual Coal

The principle of roadway layout is in the low stress zone. Roadway will be difficult to support due to the lower seam face in the close multi-seam is affected by dynamic pressure of the upper seam face mining. The distribution of abutment pressure after the upper seam face mining were analyzed,concluded that: The layout of lower seam roadway should avoid the stress concentration area of residual coal pillar; Stress concentration of the coal pillar is related with mining order, and stress concentration degree is higher in the first mining side of the coal pillar; when the upper coal seam is gob, the layout of the roadway in the lower coal seam with the pattern of homodromous alternate interior layout will be easy to support.

scholarly journals Evolution Law of Coal Seam Abutment Pressure under the Influence of Shallow Buried Complex Strata: A Case Study

2021 ◽  
Vol 2021 ◽  
pp. 1-13
Author(s):  
Buchu Zhang ◽  
Dequan Sun ◽  
Ruiliang Zheng
Keyword(s):  
Stress Concentration ◽  
Plastic Zone ◽  
Coal Seam ◽  
Dynamic Load ◽  
Abutment Pressure ◽  
Physical Simulation ◽  
Limit Equilibrium ◽  
Coal Pillar ◽  
Evolution Law ◽  
Coal Wall

The evolution law of lateral abutment pressure under the condition of fully mechanized mining in shallow coal seam is studied using the change process of coal pillar stress in disturbed section as the research object. The results of physical simulation experiment show that, after coal mining, due to the collapse of coal seam roof, the overlying strata of key layer will disturb the section coal pillar to different degrees, and the sudden change of degrees of abutment pressure near the coal wall reaches the maximum. Affected by the energy released by the fracture of key stratum, the stress mutation area shifts to the coal wall at a deeper level and the range of plastic zone increases. From the perspective of the numerical simulation, according to the change characteristics of coal pillar abutment pressure in the mining process, the dynamic load process of complex roof strata is divided into three stages: the stage not affected by mining, the stage of dynamic load action, and the stage of static load. In the first stage, the lateral abutment pressure is only affected by the roadway mining, causing stress concentration in the coal body. The stress concentration coefficient is small, and the supporting stress is stable. In the second stage, with the advance of the working face, the coal seam load changes continuously owing to the movement of overlying rock in the goaf, and the lateral abutment pressure changes evidently under the influence of dynamic load. In the third stage, the overlying load forms stress concentration in the coal seam and continuously transfers to the coal wall at a deeper level, which increases the limit equilibrium area of coal body. During this period, the range of plastic zone still increases at a certain rate for a period of time and finally tends to be stable.

scholarly journals Study on the Rheological Failure Mechanism of Weakly Cemented Soft Rock Roadway during the Mining of Close-Distance Coal Seams: A Case Study

2020 ◽  
Vol 2020 ◽  
pp. 1-20
Author(s):  
Wenkai Ru ◽  
Shanchao Hu ◽  
Jianguo Ning ◽  
Jun Wang ◽  
Qingheng Gu ◽  
...  
Keyword(s):  
Coal Seam ◽  
Failure Mechanism ◽  
Coal Pillar ◽  
Soft Rock ◽  
Western China ◽  
Creep Failure ◽  
Mining Areas ◽  
Geological Conditions ◽  
Residual Coal ◽  
Close Distance

During the mining of the shallow-buried and close-distance multiple coal seam, the rheological failure of the surrounding weakly cemented soft rock of the roadway in the lower coal seam under the concentrated stress is very rare. However, the stress on the roof of the upper coal seam is transmitted down through the residual pillar, resulting in this situation. Taking the Gaojialiang coal mine which is located in the mining areas of western China as the research object, the failure mechanism of the roadway roof under the residual coal pillar in the shallow-buried and close-distance multiple seam is studied in combination with field monitoring and numerical simulation. Furthermore, suggestions on the roadway support under such geological conditions are proposed. The results show that the residual coal pillar in the working face of the lower coal seam gradually collapses during the mining of the shallow-buried and close-distance multiple coal seam. The concentrated stress transferred by the coal pillar increases further, which makes the roof stress of the lower coal seam roadway to increase continuously. In addition, the stress of the roadway roof also increases further due to the rotation of the broken rock above the goaf, and the peek region of stress moves to the nongoaf area. Combining the heavy concentrated stress and weakly cemented property, the shallow-buried surrounding rock shows rheological behavior and failure. Therefore, we must pay more attention on the creep failure of the roadway roof under the action of the residual coal pillar even in the shallow-buried coal seam.

Numerical Analysis for the Influence of Mining Deep Coal Seam on Oversize Normal Fault

2014 ◽  
Vol 1073-1076 ◽  
pp. 2112-2116
Author(s):  
Xin Xian Zhai ◽  
Shi Wei Zhang ◽  
She Jun Ma ◽  
Guang Sen Li
Keyword(s):  
Coal Seam ◽  
Abutment Pressure ◽  
Water Inrush ◽  
Coal Pillar ◽  
Normal Fault ◽  
Mine Safety ◽  
Coal Face ◽  
Safety Production ◽  
Floor Water Inrush ◽  
The Stability

The F2 fault Guo in Tianyu Coal Mine belongs to the oversize normal fault, and mining deep coal seam has an influence on the floor water-inrush. Therefore, study the reasonable width of the fault protected coal pillar is a great significance for the mine safety production. With different advance distances of coal face into the fault hangingwall, the authors, by FLAC numerical calculation, studied the characteristics of plastic zone and stress field in front of the coal face. The results show that influence zone scope of moving abutment pressure is about 70~ 80m. The fault is still in the pressure-relief area when it is in the moving abutment pressure zone. The conclusion is conducive to the stability of F2 fault Guo, to prevent the floor from water-inrush, when the reasonable coal pillar width of the fault is wider than 80m.

scholarly journals Identification for Abutment Stress by Drilling Cuttings

2021 ◽  
Vol 11 (20) ◽  
pp. 9467
Author(s):  
Jian Tan ◽  
Yunliang Tan ◽  
Zihui Wang ◽  
Yubao Zhang
Keyword(s):  
Stress Concentration ◽  
Coal Seam ◽  
Rock Burst ◽  
Abutment Pressure ◽  
High Stress ◽  
Coal Seams ◽  
Cutting Test ◽  
Key Factor ◽  
Distribution Of Stress ◽  
The Relationship

The concentration of abutment pressure acting on coal seams induced by mining is a key factor to trigger rock burst. Understanding of abutment pressure or stress concentration is fundamental in preventing and controlling rock burst. The influence on abutment pressure fluctuation caused by the inhomogeneity of coal seams needs to be considered, but it is difficult to obtain by the present usual ways such as acoustic transmission, electromagnetic wave transmission, etc. In this article, the relationship between the amount of cuttings drilled in a coal seam and stress level was analyzed by considering the effect of drilling cutting expansion, and the drilling cutting test was carried out in Xinglongzhuang Coal Mine, Shandong Energy Ltd. It is found that the amount of cuttings drilled is positively related to the degree of stress concentration in both the plastic fracture zone and elastic zone. The amount of drilling cuttings is closely related to the roof weighting. In addition, the irregular fluctuation of drilling cuttings is an approximate map of distribution of stress concentration because of the non-uniformity of cracks and other defects in the coal seam. In order to meet the need of rock burst prevention by accurate pressure relief in high-stress zones, enough boreholes are needed.

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 Ground Stress Distribution and Dynamic Pressure Development of Shallow Buried Coal Seam Underlying Adjacent Room Gobs

2021 ◽  
Vol 2021 ◽  
pp. 1-11
Author(s):  
Ming Zhang ◽  
Chen Cao ◽  
Bingjie Huo
Keyword(s):  
Stress Distribution ◽  
Theoretical Analysis ◽  
Coal Seam ◽  
Dynamic Pressure ◽  
Coal Pillar ◽  
Horizontal Stress ◽  
Working Face ◽  
Ground Stress ◽  
Stress Environment ◽  
Coal Pillars

The condition of the coal pillars remained in the room-and-pillar gobs is complicated. The stresses loaded on the pillar floor may be transmitted and overlapped. It changes the stress environment of the lower coal seam roof, leading abnormal periodic weighting. In the procedure of coal seam 3−1 mining in the Huoluowan Coal Mine, the ground stress is high while the working face passing through the room pillars of overlying coal seam 2−2, leading to hydraulic shield being broken. In this paper, theoretical analysis, numerical calculation, and similar material simulation were used to analyse the stress environment of lower seam and the effect of coal pillars remained in close-distanced upper seam. The stress transfer model was established for the room pillars of coal seam 2−2, and the stress distribution of underlying strata was obtained based on theoretical analysis. The joint action of dynamic pressure of high stress-coal pillar with movement of overlying rock strata in the working face 3−1 under the coal pillar was revealed. The results showed that the horizontal stress and vertical stress under the large coal pillar of the room gob in coal seam 2−2 were high, being from 9.7 to 15.3 MPa. The influencing depth of vertical stress ranged from 42 m to 58 m. The influencing depth of horizontal stress ranged from 10 to 23 m. The influencing range of the shear stress was from 25 to 50 m. When the working face 3−1 was mined below the coal pillar of 20 m or 50 m, abutment pressure was relatively high. The stress concentration coefficient reached 4.44–5.00. The dynamic pressure of the working face was induced by the stress overlying of the upper and lower coal seams, instability of the inverted trapezoid rock pillar above the coal pillar, and collapsing movement of the roof. The studying results were beneficial for guiding the safety mining of the coal seam 3−1 in the Huoluowan Coal Mine.

Study on Energy and Stress of Irregular Failure Zone of Upper Layered in Slice Mining

2013 ◽  
Vol 734-737 ◽  
pp. 828-832
Author(s):  
Xiao Biao Zhang ◽  
Kun Zhou ◽  
Hai Tao Li ◽  
Jiao Xia Liu ◽  
Yun Yi Zhang
Keyword(s):  
Numerical Simulation ◽  
Stress Concentration ◽  
Coal Pillar ◽  
Simulation Software ◽  
Failure Zone ◽  
Surrounding Environment ◽  
Production Safety ◽  
Residual Coal ◽  
Delamination Area ◽  
Slice Mining

Under the condition of the top layered have irregular zone , due to the stress concentration caused by the upper leaf residual coal pillar , lower leaf will increase recovery difficult. This article reappear the scene of irregular top delamination area and the surrounding environment by FLAC3D numerical simulation software, receive the distribution condition of stress, displacement and the elastic energy of media under this condition, provide abundant basis for develop highly targeted production safety measuresa, solve the problem of data range is smaller,because the restriction of the detection equipment and other technical reasons detection equipment under the scene.

scholarly journals Study on Pressure Relief Technology of High-Pressure Water Jet of Residual Coal Pillar in Overlying Goaf in Close Seam Mining

2022 ◽  
Vol 2022 ◽  
pp. 1-19
Author(s):  
Shang Yang ◽  
Xuehui Li ◽  
Jun Wang ◽  
Shuhao Yang ◽  
Zhen Shen ◽  
...  
Keyword(s):  
High Pressure ◽  
Coal Seam ◽  
Coal Pillar ◽  
Water Jet ◽  
Hydraulic Support ◽  
Working Face ◽  
Pressure Water ◽  
High Pressure Water Jet ◽  
Residual Coal ◽  
Close Distance

To solve the problem of strong ground pressure behaviour under a residual coal pillar in the overlying goaf of a close-distance coal seam, this paper proposes the technology of weakening and relieving the residual coal pillar in the overlying goaf by a high-pressure water jet. Based on the geological occurrence of the No. 3 coal seam and mountain No. 4 coal seam in the Yanzishan coal mine, the high-pressure water jet pressure relief technology of residual coal pillars in the overlying goaf of close-distance coal seams was studied by theoretical analysis and field industrial tests. First, the elastic-plastic zone of the residual coal pillar and the stress distribution law of the floor are obtained by theoretical analysis, and the influence degree of the residual coal pillar on the support of the lower coal seam working face is revealed. Then, a high-pressure water jet combined with mine pressure is proposed to weaken the residual coal pillar. Finally, through the residual coal pillar hydraulic cutting mechanical model and “double-drilling double-slot” model, the high-pressure water jet drilling layout parameters are determined, and an industrial field test is carried out. The single knife cutting coal output and 38216 working face hydraulic support monitoring data show that high-pressure hydraulic slotting can weaken the strength of the coal body to a certain extent, destroy the integrity of the residual coal pillar, cut off the load transmission path of the overlying strata, and reduce the working resistance of the hydraulic support under the residual coal pillar to a certain extent, which is beneficial to the safe mining of the working face.

scholarly journals A Method for Determining Feasibility of Mining Residual Coal above Out-Fashioned Goaf under Variable Load: A Case Study

2020 ◽  
Vol 2020 ◽  
pp. 1-12
Author(s):  
Yuxia Guo ◽  
Honghui Yuan ◽  
Xiaogang Deng ◽  
Yujiang Zhang ◽  
Yunlou Du ◽  
...  
Keyword(s):  
Coal Seam ◽  
Coal Mine ◽  
Coal Pillar ◽  
New Method ◽  
System Model ◽  
Variable Load ◽  
Residual Coal ◽  
Seam Mining ◽  
Suspended Roof ◽  
Upward Mining

Out-fashioned goaf is the protective structure for mining the upper residual coal, and its stability is the core problem in mining the upper residual coal. According to the upward mining demand for No. 5 coal seam above the out-fashioned goaf in Baizi Coal Mine, a new method is proposed to determine the upward mining safety. According to the analysis of the actual situation of the mine, the coal pillar and suspended roof in the out-fashioned goaf are taken as the objects. Furthermore, a “coal pillar-suspended roof” system model based on the variable load induced by abutment pressure of upper coal seam mining is established. After the mechanical model was solved, the parameter acquisition method of the model was established. The basic parameters of Baizi Coal Mine were considered to determine the feasibility of mining residual coal above out-fashioned goaf. And the effects of variable load on the coal pillar and suspended roof stability were analyzed. The results show that the upper No. 5 coal seam in Baizi Coal Mine can be mined safely. Compared to the traditional method, which simplifies all the upper loads to uniform loads, the new method is safer. The system stability of the suspended roof and coal pillar is influenced by “a/L” and “L.” Axial stress curves of the coal pillar and suspended roof appear nearly parabolic with “a/L” varying. Their maximum values are obtained when the “a/L” value is around 0.5∼0.6. In this situation, the combination structure is most easy to to be damaged. The ratio q′/q has a linear relationship with all stresses of the system model. The failure sequence of the system model is determined by analyzing the relationship between the tensile strength of the suspended roof and compressive strength of the coal pillar. This study provides a reference case for coal resources upward mining under similar conditions.

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