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ABSTRACT
A large area of underground spaces form after the extraction of underground mineral resources, in which coal mining leads to billions of cubic meters of underground spaces every year. In China, there are 2,469 coal mines exist within 50 km (straight line distance) of the cities, and the annual volume of the goaf in the coal mines is 442 million m3. However, most of these spaces are filled caved rock fragmentation and can hardly be retained and used. To fill this research gap, an innovative scientific conception is proposed in this paper. High-water and quick-setting materials (HWQSMs) are used to build backfill bodies rapidly in mined-out spaces during longwall mining to retain a large amount of underground spaces. Three different methods of building cubic or cylindrical backfill bodies in the mining goaf are introduced. An integration craft and the potential backfilling materials for the construction of the underground space are described in detail. Technical and economical rationality of the proposed conception is evaluated. Further research prospects and the problems that need to be overcome to achieve this goal are discussed. The results shows that compressive strength reaches 10.5 MPa when the HWQSM specimen has a water to HWQSM ratio of 1.5 and the specimen sustains an obvious residual load-bearing capacity. Hence the backfill body will not fail instantaneously in the process of roof supporting. The average unitary underground space value is estimated to be 2,838.89 Yuan per m3, which has great economic value.
Competing interest
The authors declare no conflict of interest.
Data and materials availability
All data are available in the main text at https://github.com/UESO1747574/15567036.2020.
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Notes on contributors
Wenda Wu
Wenda Wu Ph.D candidate in China University of Mining and Technology. He received the B.Sc. and M.Sc. degrees in mining engineering from the Liaoning Technical University, Fuxin, China, in 2013 and 2016, respectively. His research interests mainly about mining pressure and ground improvement, and development of underground space construction.
Jianbiao Bai
Jianbiao Bai Professor in School of mines, China University of Mining and Technology (CUMT). He received the B.Sc., M.Sc. and Ph.D. degrees in mining engineering from the CUMT, Xuzhou, China, in 1989, 1992 and 2002, respectively. His research interests mainly about mining pressure and ground improvement, the technology of gob-side entry retained and pillar design.
Shuai Yan
Shuai Yan Associate Professor inSchool of mines, China University of Mining and Technology (CUMT). He received the B.Sc., M.Sc. and Ph.D. degrees in mining engineering from the CUMT, Xuzhou, China, in 2007, 2009 and 2013, respectively. His research interests are Rock Mechanics and Mining Technology.
Xiangyu Wang
Xiangyu Wang Professor in School of mines, China University of Mining and Technology (CUMT). He received the B.Sc., M.Sc. and Ph.D. degrees in mining engineering from the CUMT, Xuzhou, China, in 2002, 2005 and 2008, respectively. His research interests mainly about development of underground space course design and teaching methods for the knowledge of underground traffic, underground storage relating to underground space development significance, design, construction, management, property rights using classroom teaching, group discussion and video presentation.
Bowen Wu
Bowen Wu Ph.D candidate in China University of Mining and Technology (CUMT). He received the B.Sc. degree from the Anhui University of Science and Technology, Huainan, China, in 2015 and M.Sc. degree in mining engineering from the CUMT, in 2015. His research interests mainly about support technology for gob-side entry and hydraulic fracturing.