Test research on advance abutment pressure caused by coal mining based on optical fiber monitoring

Abstract The advance abutment pressure on the coal mining face of a deep stope plays a decisive role in the surrounding rock instability, rock burst and coal-gas outburst. Based on distributed optical fiber sensing technology and theoretical analysis of the stress state, the distribution characteristics of the advance abutment pressure were tested. Taking the 61103 coal mining face of a mine in Inner Mongolia as an example, downhole measurement research was carried out. Based on the monitoring data, a two-dimensional (2D) geological model for the distribution of the advance abutment pressure during the mining process was developed. To verify the validity of the model, a verification borehole was located on the 61201 coal mining face of the same mining area, the two borehole datasets were comprehensively analysed and the model was corrected. The modified model shows that the influence scope of the advance abutment pressure is 0–26.5 m, the position of the peak stress is 5.1–6.4 m in front of the coal mining face and the peak stress can reach 21.98–23.98 MPa. The stress concentration coefficient is 1.22–1.91 and the vertical influence depth is 13–14 m. Moreover, the advance abutment pressure exhibits obvious zoning in the transverse direction, and the stress at the same position in front of the coal mining face will undergo a process of steady-slow increase-significant increase-peak-decrease. The technical parameters obtained from this study can be used for other coal mining faces in the area. In addition, the testing result of the abutment pressure from the distributed optical fiber sensors is effective and can provide a new research method for mine safety monitoring.

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Motion model and key parameters of overburden strata in longwall filling face

E3S Web of Conferences ◽

10.1051/e3sconf/202130301022 ◽

2021 ◽

Vol 303 ◽

pp. 01022

Author(s):

Zengde Yin ◽

Jinxiao Liu ◽

Feng Zhang ◽

Yongle Liu ◽

Wenxin Li

Keyword(s):

Coal Mining ◽

Water Body ◽

Abutment Pressure ◽

Simulation Method ◽

Karst Water ◽

Motion Model ◽

Filling Rate ◽

Technical Parameters ◽

Working Face ◽

Overburden Strata

When the paste material is filled into the longwall working face of the coal mine, it firstly controls the movement of the overburden strata, thereby limiting the movement of the far field rock layer and reducing the subsidence. With this regard, the paste filling technology of the long-wall mining can address the limitation of “three down, one up” (mining under water body, building and rail, and on karst water body) technology in coal mining, thus improving the extraction rate of coal resource. To control the movement of the overburden strata near the working face, the prerequisite is to clarify the relationship among the parameters, including coal mining thickness, filling body thickness, filling step, filling body strength, etc. On this basis, this paper established an overall mechanical model of the filling body and surrounding rock, and determined the key technical parameters of the overburden movement, i.e., the filling rate, the strength of the filling body, and the filling step. Then, the influence of these parameters on the overburden movement and abutment pressure was analyzed through the numerical simulation method. The results show that at a higher filling rate, the overburden motion can be better controlled; the filling step only had a significant effect on the roof subsidence within the relevant step; as the early strength of the filling body was higher, the overburden subsidence was smaller and the abutment pressure in front of the face was better controlled. The research of overburden motion model and its key parameters have a good guiding significance for paste filling in the longwall face of coal mines.

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The Field Monitoring Experiment of the Roof Strata Movement in Coal Mining Based on DFOS

Sensors ◽

10.3390/s20051318 ◽

2020 ◽

Vol 20 (5) ◽

pp. 1318 ◽

Cited By ~ 3

Author(s):

Tao Hu ◽

Gongyu Hou ◽

Zixiang Li

Keyword(s):

Optical Fiber ◽

Coal Mining ◽

Coal Mine ◽

Shanxi Province ◽

Transfer Performance ◽

Test Results ◽

Strata Movement ◽

Strain Transfer ◽

Study Results ◽

Roof Strata

Mining deformation of roof strata is the main cause of methane explosion, water inrush, and roof collapse accidents amid underground coal mining. To ensure the safety of coal mining, the distributed optical fiber sensor (DFOS) technology has been applied in the 150,313 working face by Yinying Coal Mine in Shanxi Province, north China to monitor the roof strata movement, so as to grasp the movement law of roof strata and make it serve for production. The optical fibers are laid out in the holes drilled through the overlying strata on the roadway roof and BOTDR technique is utilized to carry out the on-site monitoring. Prior to the on-site test, the coupling test of the fiber strain in the concrete anchorage, the calibration test of the fiber strain coefficient of the 5-mm steel strand (SS) fiber, and the test of the strain transfer performance of the SS fiber were carried out in the laboratory. The approaches for fiber laying-out in the holes and fiber’s spatial positioning underground the coal mine have been optimized in the field. The indoor test results show that the high-strength SS optical fiber has a high strain transfer performance, which can be coupled with the concrete anchor with uniform deformation. This demonstrated the feasibility of SS fiber for monitoring strata movement theoretically and experimentally; and the law of roof strata fracturing and collapse is obtained from the field test results. This paper is a trial to study the whole process of dynamic movement of the deformation of roof strata. Eventually the study results will help Yinying Coal Mine to optimize mining design, prevent coal mine accidents, and provide detailed test basis for DFOS monitoring technique of roof strata movement.

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