Analysis on the Breaking Law of Soft and Thick Roof of Fully Mechanized Top-Coal Caving Face
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ORIGINAL PAPER
Analysis on the Breaking Law of Soft and Thick Roof of Fully Mechanized Top-Coal Caving Face Dezhong Kong . Qiang Li
. Nan Wang . Guiyi Wu
Received: 22 February 2020 / Accepted: 2 June 2020 Ó Springer Nature Switzerland AG 2020
Abstract The study of roof breaking law is very important for the behavior of the underground pressure in fully mechanized top-coal caving face under the condition of weak roof. In this paper, the research is to study the soft and thick roof breaking law in the fully mechanized top-coal caving face 2–100 in coal seam 2#. The theoretical analysis, numerical simulation and field measurement methods are used to analyze the breaking law of the weak thick layer roof in the fully mechanized top-coal caving face. First, the mining conditions of the working face are introduced systematically, the mechanical properties of the weak roof are analyzed, the mechanical model of the immediate roof caving structure and the mechanical model of the main roof fracture structure are established, and the instability characteristics of the immediate roof and the main roof are analyzed. Through UDEC numerical simulation, the failure structure of the soft and thick roof in fully mechanized caving face, the plastic zone and stress distribution of the roof under different propulsive lengths, and the roof subsidence of the basic roof are obtained. It is found that the immediate D. Kong Q. Li (&) G. Wu Mining College of Guizhou University, Guiyang 550025, China e-mail: [email protected] D. Kong N. Wang Faculty of Resources and Safety Engineering, China University of Mining and Technology (Beijing), Beijing 100083, China
roof caving will form an ‘‘arch’’ structure, and the main roof fracture will form a ‘‘three hinge arches’’ structure. Under this mine condition, the initial roof caving step is 17.8 m, and the main roof initial fracture step is 41.3 m, the periodic fracture step distance is 16.7 m. Under the condition of instability of immediate roof ‘‘arch’’ structure, when the displacement distance of the vault reaches 5.1 m, the ‘‘arch’’ structure will be unstable. Conditions of sliding instability of main roof ‘‘three hinge arches’’ structure: the ratio of coal seam thickness to the span of main roof is less than 0.2, and when the back angle is less than 8°, it is not easy to slip and lose stability. Through the observation of the field measurement results of fully mechanized top-coal caving face 2–100, the breaking rule of the soft and thick roof in fully mechanized top-coal caving face is verified. Keywords Fully mechanized top-coal caving face Soft and thick roof Numerical simulation Breaking law
1 Introduction Fully mechanized top-coal caving mining technology is the development direction of mining technology in thick coal seam mining area (Wang 2005, 2013; Cheng et al.2019a; Wu 1999). The low recovery rate
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Geotech Geol Eng
of top coal is a big problem in top coal caving mining. In addition, roof breaking law is also a key pr
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