Effect on Top-Coal Mass Failure under Load–Unload Induced by Shield Support

Author:

Ding Pengchu1ORCID,Wang Hao2ORCID,Zhao Jianjian34,Yan Shiheng1,Chang Liwu1,Li Zhen1,Zhou Changtai5,Han Dong6,Yang Jie7

Affiliation:

1. College of Intelligent Construction and Civil Engineering, Zhongyuan University of Technology, Zhengzhou 450007, China

2. School of Civil Engineering, Zhengzhou University of Technology, Zhengzhou 450044, China

3. Zimasco Private Limited, Harare 00263, Zimbabwe

4. College of Energy and Mining Engineering, China University of Mining and Technology (Beijing), Beijing 100083, China

5. Department of Architecture and Civil Engineering, City University of Hong Kong, Hong Kong 999077, China

6. Department of Northwest Geological Exploration Institute, China Metallurgical Geology Bureau, Xi’an 710119, China

7. Institutes of Science and Development, Chinese Academy of Sciences, Beijing 100190, China

Abstract

Prior to being released, the top coal of a fully mechanized caving face typically experiences the effects of mining-induced pressure and disturbances from the hydraulic support’s canopy. To investigate the promoting effect of canopy disturbances in the support-controlled area on the damage of top coal during fully mechanized top-coal caving mining, block instability theory and discrete block numerical simulation methods were employed. The instability modes during the initial support and cyclic disturbance stages were analyzed. The fracture evolution and displacement distribution curves were studied for coal bodies with strengths of 3.1 MPa, 15.0 MPa, and 29.5 MPa under the mining influence and support strengths of 0.5 MPa, 1.0 MPa, and 1.5 MPa during the initial support and cyclic disturbance processes. The results showed that during the initial support stage, the instability of the block-structured coal body exhibited four modes as follows: inter-block breakage, inter-block delamination, intra-block fracture expansion, and inter-block sliding. During the cyclic disturbance stage, the coal body instability showed three modes as follows: inter-block sliding, intra-block fracture expansion, and inter-block rotation. The disturbance from the support had little impact on the fragmentation of both low-strength and high-strength coal bodies. However, small support forces combined with multiple cycles of disturbance had an enhancing effect on the instability of medium-strength block-structured top coal.

Funder

National Natural Science Foundation of China

Key Scientific and Technological Projects of Henan Province

Basic Research Fund of Zhongyuan University of Technology

Publisher

MDPI AG

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