Application of the complex variable function method in solving the floor heave problem of a coal mine entry
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ORIGINAL PAPER
Application of the complex variable function method in solving the floor heave problem of a coal mine entry Jing-Hu Yang 1,2 & Gao-Feng Song 3
&
Yi Yang 1 & Zeng-Qiang Yang 1
Received: 23 July 2017 / Accepted: 24 August 2018 # Saudi Society for Geosciences 2018
Abstract With the increase of mining depth in Chinese coal mines, the entry floor heave becomes one of the major engineering problems. This paper has studied the stress and displacement distribution around an entry in Buertai coal mine, China. The mechanism of floor heave is analyzed using the method of complex variable function. The influences of floor mechanical properties, longwall face advance, and mine water on the stability of the floor are then identified. The results show that (1) the floor moves towards the center under the concentration of the tangential stress, resulting in floor heave; (2) the floor stability is mainly influenced by the mechanical properties of the floor and the confining stress from the surrounding rock; and (3) the unnoticeable movement of the floor may be enlarged by the mining activity (face advance) and mine water. The proposed theoretical model is validated by the numerical modeling and the in situ. Good agreements are found between the theoretical analysis and the numerical modeling results and the in situ. It is thus believed that the complex variable function method can be used for analyzing the floor heave problem. Based on the mechanism of floor heave, we divide the control techniques into two categories: creation of a stress-relief entry and floor reinforcement. The techniques were practiced at two Chinese coal mines with good ground control effects. Keywords Floor heave . Complex variable function . Numerical modeling . Control technique
Introduction After the use up of the coal resources in the shallow coal mines, China will have to mine those at the deep. In recent years, the mining depth of Chinese coal mines is increasing at a rate of 8–12 m/year. Some of the coal mines have reached the depth of 1000–1500 m. However, one of the major ground control issues in a deep coal mine is the deformation and maintenance of the entries. The roof-floor convergence is commonly used as an important parameter to describe the damage of the entry. Floor heave, however, may account for
* Gao-Feng Song [email protected] 1
School of Resource and Safety Engineering, China University of Mining and Technology (Beijing), Beijing 100083, China
2
Beijing Key Laboratory for Precise Mining of Intergrowth Energy and Resources, China University of Mining and Technology (Beijing), Beijing 100083, China
3
School of Civil Engineering, North China University of Technology, Beijing 100144, China
66.7–75% of the total amount of the convergence (Jiang et al., 2004). The floor heave has a negative impact on the transportation of coal and other materials and the mine ventilation. In some cases, the floor heave may lead to the functional failure of the entry or even casualties. The problem of the floor heave has been e
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