Structural Characteristics of the Overlying Strata in a Fully Mechanized Longwall Face with the Low-Position Thick-Hard
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ORIGINAL PAPER
Structural Characteristics of the Overlying Strata in a Fully Mechanized Longwall Face with the Low-Position Thick-Hard Roof Xinshuai Shi . Hongwen Jing . Zhenlong Zhao
Received: 20 February 2020 / Accepted: 27 April 2020 Ó Springer Nature Switzerland AG 2020
Abstract Strata activity is enhanced in the condition of the thick seam and large mining height, which increases the difficulties in roof management. A detailed understanding of roof structure characteristics and its movement law is a key to control the strata behavior. Since the existing formula hardly applies to some specific cases of geological conditions, such as the condition of a fully-mechanized longwall face with the low-position thick-hard roof in Suancigou Mine, a new formula of distinguishing structural characteristics of key strata based on a mechanical model of rock beam in periodic motion was proposed. Considering the relationship between the allowed rotating space of key strata and its limited rotation, the judgment criterion whether a cantilever beam can be formed was established. Also, a method for calculating the reasonable working resistance of hydraulic supports under these special roof structure was deduced from the angle of preventing rotating instability of the main roof. A field application was performed at 6-105-2 working face, and the proposed judgment criterion indicated that the LPTHR would break in the form of a voussoir beam structure at the Z1 drilling area, while at Z2 and Z3 drilling area, the broken LPTHR would
X. Shi H. Jing (&) Z. Zhao State Key Laboratory for Geomechanics and Deep Underground Engineering, China University of Mining and Technology, Xuzhou 221116, People’s Republic of China e-mail: [email protected]
behave as the cantilever structures. Field monitoring results showed that the limit-rotation-based cantilever structure criterion could accurately discriminate the structural characteristics of LPTHR. According to the calculation formula of support resistance of hydraulic support, the reasonable working resistance of hydraulic supports in 6-105-2 working face was determined to be 16,245 kN. Keywords Roof structure characteristics Key strata Cantilever beam Working resistance of hydraulic support
1 Introduction Currently, fully mechanized caving coal mining technology with large mining height has been widely used in China (Gong and Jin 2004; Li et al. 2014; Guo et al. 2017; Xie et al. 2018; Xue et al. 2020), which significantly promotes the productivity and efficiency. However, with the increase of the mining height, the damage areas of mining-induced strata are enlarged. The strata behaviors are significantly different from the conventional fully mechanized coal faces, leading to a series of new issues, such as support crushing, rib spalling, roof caving, etc. Therefore, it is of considerable significance to have a deep understanding of the roof structural characteristics of the fully-mechanized
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Geotech Geol Eng
caving face
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