Abstract
In order to provide a theoretical basis for the design of underground shaft coal pocket and support parameters in coal mines, a mechanical model and a dynamic analysis of the silo wall are established based on the engineering background of Ganhe Coal Mine. The numerical calculation is carried out by using the new model. The back analysis of the silo wall damage in the actual project is carried out, and the deformation law and fracture mechanism of the silo wall affected by different lateral pressure coefficients are analyzed and studied research. Based on the Mohr–Coulomb strength criterion, five sets of orthogonal simulation experiments were carried out for lateral pressure coefficients of 0.6, 0.8, 1.0, 1.2, and 1.4, respectively. The results show that the lateral pressure coefficient is the main factor affecting the deformation of the silo wall, the radial displacement of the silo wall increases gradually with the increase of the lateral pressure coefficient, and the displacement follows the quadratic polynomial function distribution. The maximum tensile stress area of the silo wall is located in the middle and lower part of the shaft coal pocket, which better explains the engineering phenomenon that the actual fracture location of the silo wall is mostly concentrated in the middle and lower part of the underground shaft coal pocket. The targeted repair technology can be used for reference in engineering.
Highlights
Background e Ganhe CoalMine is located in the north of Huozhou mining area in Huoxi coalfield, Shanxi Province, and its administrative division is under the jurisdiction of Hongtong County, Linfen City. e shape of the minefield is NESW long strip distribution. e length of NE-SW is about 9 km, and the width of NW-SE is about 4 km, with an area of 35.559 km2.Ganhe Coal Mine shaft coal pocket is the only one in this mine
It is located at 24.5 m West by north of the main shaft, with a net diameter of Φ 7 m and a height of 47.39 m. e level of the upper coal bunker opening is +79.8 m and the Earth’s surface level is +546.4 m. e silo wall is made of C20 plain concrete arch with a supporting thickness of 450 mm and a capacity of 1700 m3, which is a high-capacity shaft coal pocket. e construction of the shaft coal pocket began in December 2007 and was completed in February 2008. e bunker body was damaged for the first time in 2011, collapsed gradually, and became serious from the end of 2015 to April 2016
According to the observations on May 25, 2016, and June 2, 2016, the damaged section is located at the level of +44.8 m to +62.8 m, with the maximum collapsed areas depth of 5 m and height of 7-8 m. e damage and collapse direction are mainly in the south side and some extend to the east and west sides of the shaft coal pocket. e serious collapse area accounts for two-thirds of the section perimeter, and the surrounding rock collapsed areas volume reaches about 1000 m3
Summary
Based on the actual engineering practice of Ganhe mine, the rock mechanical model can be constructed as Figures 1(a) and 1(b). e size and end effect of the coal bunker upper end was ignored to highlight the stress state of the silo wall. Based on the actual engineering practice of Ganhe mine, the rock mechanical model can be constructed as Figures 1(a) and 1(b). E overlying strata which are not simulated here are simplified as uniformly distributed loads applied on the upper boundary of the model. Is can be classified into three cases: (1) perfect contact, (2) hinged contact between upper and lower ends, and (3) partial contact between silo wall and surrounding rocks, where case 2 was the most unfavorable and prone to deformation and damage. Underground sha coal pocket p p Unconformity contact between silo wall and surrounding rock. Model of the silo wall and inclusion of the surrounding rocks are depicted in Figures 1(c) and 1(d), respectively. Based on the novel established model, the mechanical analysis is conducted via the theoretical research and numerical experiment
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