Utilizing concrete pillars as an environmental mining practice in underground mines

Ground control is an integral element of mine design and worker safety. The use of concrete pillars for underground mines is of paramount importance to maintaining the economic and operational security of structures. This paper deals with the use of fiber-reinforced concrete (FRC) as pillars via laboratory and field tests. The strength performance of prepared concrete reinforced with glass, polypropylene and polyacrylonitrile fibers was researched by a mechanical press and a computed tomography (CT) tool. Samples were tested for fiber volume fractions of 0, 0.4, 0.8 and 1.2 wt%, respectively. Results have indicated that, with the addition of fibers, the strength was improved first due to a bridging effect and then decreased due to a pull-out effect. Compared to the reference sample, the absorbed energy prevents FRC from deterioration by mechanisms of matrix cracking, fiber-matrix interface debonding and fiber rupture. The peak strains of FRC linearly rise with increasing fiber. The gray value distribution curves have also good correspondence with 2D CT pore and crack distributions, which reveal that gray value processing could depict the structural behavior of concretes reinforced with or without fiber. Theoretical analyses show that the pillar remains stable for sustainable mining. Besides, the location and size of FRC pillars are suitable for numerical calculations of the trial stope. The findings of this study can offer a key reference for the orebody pillar recovery in underground mines. © 2020 Elsevier LtdLNM202009 National Natural Science Foundation of China: 51974012, 51804017 Fundamental Research Funds for the Central UniversitiesThis work was financially supported by the National Natural Science Foundation of China (grant numbers: 51804017 and 51974012 ), the Open Fund of State Key Laboratory of Nonlinear Mechanics (grant number: LNM202009 ) and Fundamental Research Funds for the Central Universities (Grant No. FRF-TP-20-001A2 and FRF-BD-19-005A )