Development of a combined mining technique to protect the underground workspace above confined aquifer from water inrush
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ORIGINAL PAPER
Development of a combined mining technique to protect the underground workspace above confined aquifer from water inrush disaster Shengchao Yu 1,2,3 & Jingmin Xu 4 & Weibing Zhu 1,2 & Sihua Wang 2 & Wenbing Liu 2 Received: 26 August 2019 / Accepted: 8 April 2020 # The Author(s) 2020
Abstract One task facing by the geotechnical engineers is to protect the workspace in an underground construction/excavation site from various forms of geological disasters, such as the water inrush, rock burst, and collapse of the surrounding rock/soil. In this paper, a combined controlling measure was proposed based on underground mining and water environment: the method of strip mining has been initially proposed as an effective measure against underground workspace floor failure when mining above confined aquifer in the Bucun coal mine, China, and however, its ability to avoid floor water inrush has yet to be demonstrated; in the next step, field trials using caving zone backfill technology to prevent underground workspace floor failure and excavate retained strip coal pillars were implemented based on the theoretical calculation and numerical simulation results. Engineering practice showed that the failure depth of the underlying strata of the workspace had no growth without the possibility of water inrush, and the safety of the underground space was achieved. Thus, this study represents a successful attempt to develop the combined strip mining and caving zone backfilling technique to ensure the safety of the underground workspace and control surface subsidence when excavating the retained strip coal pillars above confined aquifer. The proposed combined technique can also be used in other underground excavation activities with similar problems. Keywords Underground workspace safety . Floor water inrush . Strata failure depth . Combined technique . Strip mining . Caving zone backfilling
Notationa list Bul (Pa) Bulk modulus of strata CP (m) Failure depth of seam floor after strip mining Coh (Pa) Cohesion of strata d (m) Depth of strata
* Jingmin Xu [email protected]
D1 (m) D2 (m) Den (kg/m3) F (–) Fric (deg) Gro (–) h (m) H (m) M (m) n (–)
1
State Key Laboratory of Coal Resources and Safe Mining, China University of Mining and Technology, Xuzhou 221116, China
2
Key Laboratory of Deep Coal Resource Mining, Ministry of Education of China, School of Mines, China University of Mining and Technology, Xuzhou 221116, China
3
Department of Earth Sciences, The University of Hong Kong, Hong Kong 999077, China
P (MPa)
Department of Civil Engineering, Faculty of Engineering, University of Nottingham, University Park, Nottingham NG7 2RD, UK
Pp (MPa)
4
Depth of each drilling borehole Distance between coal seam and each aquifer Density of strata Safety factor of coal pillar Internal friction angle of strata Layer no. group of strata Mining height of working face Cover depth of coal seam Thickness of aquiclude A constant that depends on the ratio of width to height of the retained coal pillar Water pressure s
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