Numerical Analysis of Support Designs Based on a Case Study of a Longwall Entry
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The stability of the entries of longwall panels is a major concern in underground coal mines. While panel entries have a short service life, they must be well supported to sustain the mining-induced loads during panel extraction. In this paper, a panel-wide numerical model was built with FLAC3D to examine a longwall panel entry with poor stability. The processes of entry development and panel retreat mining are simulated with three different entry support designs: the original design in the field and two newly proposed designs. The ground stability in each support condition was examined and compared in terms of ground deformation and extent of failure. A field test was then conducted to compare the three support designs. An instrumentation program was put in place in the field, and monitoring results were used to validate the numerical models. An optimal support design under the associated geological and geotechnical conditions was obtained. The underlying support mechanism was further analyzed with numerical modeling in the view of support-induced stress distribution in the surrounding rock mass. The results suggest that employing proper support with pre-tension generates a large area of support-induced stress in the surrounding rock mass, thereby improving the ground stability in terms of eliminating rock failure and limiting deformation. The results of this study contribute to the understanding of the role of pre-tensioned supports and can be utilized for support design and optimization under similar geological and geotechnical circumstances.
KeywordsLongwall mining Numerical simulation Roadway stability Rock bolt support Support design
List of Symbols
Plastic strain parameter at the residual strength
The research of this study was sponsored by the National Key R&D Program of China (2018YFC0604703), the National Natural Science Foundation of China (51704182, 51574155), the Natural Science Foundation of Shandong Province (ZR2017BEE050), the State Key Laboratory for GeoMechanics and Deep Underground Engineering (SKLGDUEK1725) and the Shandong University of Science and Technology. The field information from the study site was provided by the Zhaogu No. 2 coal mine, owned by Henan Energy & Chemical Industry Group Co., Ltd. The authors are grateful for their support.
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