Abstract
This study adopts the stress relief method to test the in situ stress in the field to obtain the in situ stress distribution characteristics of no. 2 + 3# coal seam. A three-dimensional model was established with the no. S3012 working face as the engineering background, and the measured in situ stress values were applied to the three-dimensional model, and the spatial-temporal evolution characteristics of coal and rock mass around the stope during coal seam mining were studied. The specific conclusions are as follows: the three-dimensional stress distribution map in front of, behind, and on both sides of the working face in the process of coal mining are obtained. As the working face goes on, the maximum value of the supporting stress formed in front of, behind, and on both sides of the working face shifts to the corner, presenting a “hump-like” distribution. The stress concentration coefficient of front, back, and both sides of stope increases linearly with the increase of the mining size. Under the same mining size, the stress concentration coefficient in front of stope is the smallest, and the stress concentration coefficient on both sides is the largest. The three-dimensional displacement field distribution nephogram of overlying strata in the process of coal mining is obtained. With the continuous advance of the working face, the roof strata of coal seam undergo the continuous dynamic subsidence process, and the roof subsidence increases continuously, showing the shape of “bowl” with sharp bottom. In the process of working face mining, the roof displacement of coal seam showed an “O” shape evolution characteristic. The three-dimensional distribution cloud map of the plastic zone of coal and rock mass in the process of the working face mining was obtained, and the failure volume of the plastic zone gradually increases with the continuous progress of the working face.
Highlights
China is one of the countries with the worst disasters in the world, especially the dynamic disasters generated in the process of coal resource mining, such as coal and gas outburst, rock burst, gas, and other disasters [1], which cause huge losses to people’s lives and property and seriously hinder the society, environment, and safe and efficient mining of coal resources. e occurrence of these disasters is closely related to the stress environment of the coal and rock mass
It is of great significance for the prevention and control of dynamic disasters such as coal and gas outburst to make clear the distribution characteristics of the stress field of the coal and rock mass and the evolution characteristics of the stress field of the surrounding rock mass during the mining process [2, 3]
E in situ stress field refers to the undisturbed natural stress field, known as the original stress field, which consists of the tectonic stress field and the self-weight stress field of coal and rock mass. e tectonic stress field is formed by geological tectonic movement, which is complex and variable with uneven stress distribution. e horizontal stress in the shallow part of the crust is generally larger than the selfweight stress, which is about 1.5–2.0 times of the self-weight stress [4], while the horizontal stress is generated by the structural stress [5]. ere are many in situ stress testing methods, among which the commonly used ones are stress relief and hydraulic fracturing [6]
Summary
China is one of the countries with the worst disasters in the world, especially the dynamic disasters generated in the process of coal resource mining, such as coal and gas outburst, rock burst, gas, and other disasters [1], which cause huge losses to people’s lives and property and seriously hinder the society, environment, and safe and efficient mining of coal resources. e occurrence of these disasters is closely related to the stress environment of the coal and rock mass. E indoor similar simulation test method can effectively study the fracture characteristics of overburden in shallow and large mining height [21, 22], Liu et al [13] analyzed the stress evolution process of the surrounding rock in the pressure relief area when mining in the short distance coal seam and believed that the stress in the floor rock in the working face decreased linearly. Scholars at home and abroad have carried out a series of research studies on the evolution characteristics of stress field of coal and rock mass, most of them are related research studies in the plane state, and most of the models are based on displacement constraints or similar simulation and numerical simulation tests under hydrostatic pressure. The working face is affected by some faults, resulting in roof fracture and coal seam missing, which causes adverse factors to the working face and has a great impact on the coal quality. e lithology of strata near no. 2 + 3# coal seam is given in Table 1, and the physical and mechanical parameters of each rock stratum are from the literature [28]
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