scholarly journals Failure Characteristics and Stability Control of Bolt Support in Thick-Coal-Seam Roadway of Three Typical Coal Mines in China

2021 ◽  
Vol 2021 ◽  
pp. 1-16
Author(s):  
Zhe Xiang ◽  
Nong Zhang ◽  
Deyu Qian ◽  
Zhengzheng Xie ◽  
Chenghao Zhang ◽  
...  
Keyword(s):  
Coal Seam ◽  
Coal Mines ◽  
Stability Control ◽  
Western China ◽  
Thick Coal Seam ◽  
Failure Characteristics ◽  
Safety Control ◽  
Geological Conditions ◽  
Roadway Safety ◽  
Bolt Failure

Roadways in thick coal seams are widely distributed in China. However, due to the relatively developed cracks and brittleness of coal, the support failure of thick-coal-seam roadways frequently occurs. Therefore, the study of bolt failure characteristics and new anchoring technology is very important for the safety control of thick-coal-seam roadways. Based on field observations, the failure mechanism of selected roadway failures under distinct conditions at three representative coal mines in eastern and western China was analyzed. Recommendations are provided for roadway safety control. The results show that the strength and dimension of the anchoring structure in the coal roof of thick-coal-seam roadways are the decisive factors for the resistance of the roadway convergence and stress disturbance. The thick anchoring structure in the roof constructed by flexible long bolts can effectively solve the problem of support failure caused by insufficient support length of traditional rebar bolts under the condition of extra-thick coal roof and thick coal roof with weak interlayers. The concepts and techniques presented in the paper provide a reference for the design of roadway support under similar geological conditions and dynamic load.

scholarly journals Deformation Rules for Surrounding Rock in Directional Weakening of End Roofs of Thin Bedrocks and Ultrathick Seams

2020 ◽  
Vol 2020 ◽  
pp. 1-12
Author(s):  
Fei Liu ◽  
Zhanguo Ma ◽  
Yongsheng Han ◽  
Zhimin Huang
Keyword(s):  
Abutment Pressure ◽  
Main Roof ◽  
Stability Control ◽  
Surrounding Rock ◽  
Western China ◽  
Resource Exploitation ◽  
Failure Characteristics ◽  
Key Strata ◽  
Working Face ◽  
Geological Conditions

With the deployment of China’s energy strategy in the western regions, complex geological mining conditions such as thin bedrock and ultrathick seams in western China have caused a series of problems such as serious deformation of the surrounding rock at the ends of the working face and the increase in the lead abutment pressure of the roadways; the research on end roof deformation in the resource exploitation in western China has become one of the great demands of the industry. Based on the failure characteristics of rock mass, relying on the actual mining geological conditions of a coal mine in Inner Mongolia, the failure characteristics of the overlying rock strata under the influence of mining were simulated and analyzed using similar material simulation experiment, which intuitively reproduced the failure and deformation processes of the immediate roof, main roof, and key strata and revealed the mechanical mechanism of the directional weakening of the end roof. It is of great significance for the stability control of the surrounding rock at the end of the fully mechanized caving face in the thin bedrocks and ultrathick seams, reducing the abutment pressure of gate roadway and controlling the spontaneous combustion of residual coal in the goaf.

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.

scholarly journals Determination of cyclic filling length in gob-side entry retained with roadside filling and its application

2020 ◽  
Author(s):  
Zizheng Zhang ◽  
Jianbiao Bai ◽  
Xianyang Yu ◽  
Weijian Yu ◽  
Min Deng ◽  
...  
Keyword(s):  
Coal Seam ◽  
Coal Mine ◽  
Difference Method ◽  
Suggested Method ◽  
Stress Difference ◽  
Thick Coal Seam ◽  
Mechanics Model ◽  
Working Face ◽  
Geological Conditions ◽  
The Relationship

Abstract Gob-side entry retained with roadside filling (GER-RF) plays a key role in achieving coal mining without pillar and improving the coal resource recovery rate. Since there are few reports on the cyclic filling length of GER-RF, a method based on the stress difference method is proposed to determine the cyclic filling length of GER-RF. Firstly, a stability analysis mechanics model of the immediate roof above roadside filling area in GER was established, then the relationship between the roof stress distribution and the unsupported roof length was obtained by the stress difference method. According to the roof stability above roadside filling area based on the relationship between the roof stress and its tensile strength, the maximum unsupported roof length and rational cyclic filling length of GER-RF. Combined with the geological conditions of the 1103 thin coal seam working face of Heilong Coal Mine and the geological conditions of the 1301 thick coal seam working face of Licun Coal Mine, this suggested method was applied to determine that the rational cyclic filling lengths of GER-RF were 2.4 m and 3.2 m, respectively. Field trial tests show that the suggested method can effectively control the surrounding rock deformation along with rational road-in support and roadside support, and improve the filling and construction speed.

scholarly journals Study of Gob-Side Entry Retaining Technology with Roof Cutting under Upper Roadway Condition

2021 ◽  
Vol 2021 ◽  
pp. 1-16
Author(s):  
Xingen Ma ◽  
Manchao He ◽  
Xuewei Sun ◽  
Jianfeng Li ◽  
Gang He ◽  
...  
Keyword(s):  
Coal Seam ◽  
Surrounding Rock ◽  
Pressure Relief ◽  
Application System ◽  
Thick Coal Seam ◽  
Working Face ◽  
Geological Conditions ◽  
Key Technologies ◽  
Releasing Effect ◽  
System Designs

Gob-side entry retaining technology with roof cutting (GERRC) has been widely used in flat and near-flat coal seam conditions, but its application under inclined coal seam is still very deficient. In order to further improve the application system of GERRC and overcome the application difficulties under special geological conditions, this paper takes the 43073 working face of Yixin coal mine as an example to research the GERRC with upper roadway under gently inclined thick coal seam. Firstly, the difficulties in the upper entry retaining with inclined coal seam are analyzed and the corresponding key technologies and system designs are put forward. Subsequently, the roof cutting and upper entry retaining are designed in detail according to geological conditions of test working face, and the roof cutting and pressure releasing effect is analyzed by numerical simulation to expound the stress distribution and pressure releasing mechanism of surrounding rock. Finally, the upper entry retaining field test is carried out to verify the feasibility and applicability of the technology and related designs. Through field monitoring, it is found that the weighting step increases significantly, the weighting strength decreases effectively on the roof cutting side, and the pressure relief effect is obvious. Meanwhile, the maximum roof to floor convergence is 361 mm and the maximum shrinkage of both sides is 280 mm, so the retained entry can meet the reuse requirement of adjacent working face.

scholarly journals Analysis of Stress Asymmetric Distribution Law of Surrounding Rock of Roadway in Inclined Coal Seam: A Case Study of Shitanjing No. 2 Coal Seam

2020 ◽  
Vol 2020 ◽  
pp. 1-14
Author(s):  
Xianyu Xiong ◽  
Jun Dai ◽  
Xinnian Chen
Keyword(s):  
Coal Seam ◽  
Stability Control ◽  
Surrounding Rock ◽  
Laboratory Model ◽  
Asymmetric Distribution ◽  
Stress Concentrations ◽  
Distribution Law ◽  
Left Wall ◽  
Failure Characteristics ◽  
Sharp Corners

Asymmetrical deformation and failure characteristics of the surrounding rock at the right-angled trapezoidal roadway in the Shitanjing No. 2 mining area has created great difficulties in the stability control and support of the roadway. First, numerical simulations were applied to systematically analyze the distribution rules for vertical stress, horizontal stress, and failure characteristics of the roadway. Furthermore, verifications were conducted via laboratory model tests and practical engineering application. The results show that the two walls of the roadway, the roof, and the sharp corners demonstrate obvious asymmetric stress concentrations. The peak value of stress concentration in the low side (right wall) is significantly greater than that in the high side (left wall), and the distances from high and low sides of roadway to both walls of the roadway are obviously different. The two sharp corners, which are symmetrical along the same direction of the coal seam inclination, show obvious compressive stresses, while the opposite directions show obvious tensile stress regions at both sharp corners; further, maximum values of the compressive and tensile stresses appear at the two corners of the roadway roof, and their magnitudes vary with the change in inclination and ground stress.

Study on Risk Evaluation of Sand Inrush of Thick Coal Seam under Water-Bearing Unconsolidated Strata

2012 ◽  
Vol 599 ◽  
pp. 769-772
Author(s):  
Hui Fu ◽  
Rui Min Feng ◽  
Hui Yu
Keyword(s):  
Coal Seam ◽  
Risk Evaluation ◽  
Water Yield ◽  
Mining Method ◽  
Thick Coal Seam ◽  
Multiple Factors ◽  
Scientific Analysis ◽  
Geological Conditions ◽  
Caving Zone ◽  
Mining Projects

For the difficulties of sand inrush of thick coal seam under water-bearing unconsolidated strata in mining projects, we carried out scientific analysis of hydro-geological conditions, including the lithology, thickness, and water yield property of water-bearing unconsolidated strata, On the basis, the heights of caving zone and water conducted zone were predicted, mining method was decided, the reasonable size of safety pillars was discussed under the condition of thick coal seam slicing mining. Based on the powerful data processing capabilities of GIS, the risk of sand inrush caused by multiple factors are analyzed quantitatively, and sand inrush risk zoning map was also analyzed eventually.

scholarly journals A case study of floor failure characteristics under fully mechanised caving mining conditions in extra-thick coal seams

2020 ◽  
Vol 17 (5) ◽  
pp. 813-826
Author(s):  
Pingsong Zhang ◽  
Yuanchao Ou ◽  
Binyang Sun ◽  
Chang Liu
Keyword(s):  
Stress Distribution ◽  
Western China ◽  
Monitoring Method ◽  
Thick Coal Seam ◽  
Failure Characteristics ◽  
Engineering Research ◽  
Object A ◽  
Working Face ◽  
Floor Failure ◽  
Inclined Boreholes

Abstract To determine the failure characteristics and evolution regularity of the floor strata during fully mechanised top-coal cave mining in typical deep and extra-thick seams in western China, the 61303 working face of an Ordos mine was selected as the engineering research object. A comprehensive monitoring method combining a BOTDR (Brillouin Optical Time-Domain Reflection) distributed fiber strain test and a borehole resistivity CT (Computerised Tomography) test was adopted. The results show that floor stress distribution of the deep-buried and extra-thick coal seam is significantly affected by the different depths of rock lithology. At the interface of the rock strata with a large difference in the elastic modulus, phenomena such as the asynchronism of strata movement and obvious differences in failure easily occur. The failure depth of the floor strata in the 61303 working face is approximately 15.90 m, and the influence depth of the floor disturbance is approximately 32.70 m. Under the influence of the mining pressure, floor stress distribution and crack evolution have obvious spatial and temporal effects. In different inclined boreholes, the data captured by the cable have different values and the fracture locations of the cable also differ. Compared with a single borehole, multiple boreholes with different inclinations, directions and locations can provide more comprehensive and reliable data trends. The knowledge obtained by this monitoring can provide reference information for the study of floor damage under similar conditions and the formulation of technical measures such as those that prevent mine water disasters.

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