Experimental study on deformation characteristics of rock and coal under stress-fluid interactions in coal mine underground water reservoir

Abstract

ABSTRACT Deformation response of rock and coal under long-term stress-fluid interactions not only directly affects the storage capacity of coal mine underground water reservoir but also seriously threatens its stability. In this paper, sandstone, mudstone, and coal fragments collected from the goaf of panel 22616 proposed underground reservoir in Daliuta coal mine were prepared to conduct experiments and to measure rock and coal bulking and compaction properties under stress-fluid interactions. Results show that the bulking factor of sandstone, mudstone, and coal fragments at loose state in order is 1.587–1.828, 1.561–1.787, and 1.435–1.753, respectively. The bulking factor of rock and coal fragments increases with the size of lumps, and that of mixed lumps is between the values of different single lumps. In addition, the bulking factor of same lumpiness rock and coal fragments with different strength is evidently different: the bulking factor of coal is the smallest, followed by that of mudstone and sandstone, respectively. Compared with natural rock and coal fragments, the bulking factor range of saturated sandstone, mudstone, and coal is 0.382–0.53, 0.41–0.627, and 0.506–0.807 with an average increase of 9.45%, 16.67%, and 13.34%, respectively. Certainly, bulking factor and axial stress of rock and coal basically satisfy the logarithmic relationship, regardless of strength, lumpiness, and water-bearing state. Mineral compositions and mesostructure characteristics of rock and coal were observed, meanwhile, quality and chemical composition of mine water were examined to clarify the relationship between internal composition, structure, and external deformation under stress-fluid interactions. These provide a theoretical basis for storage capacity estimation and stability control of coal mine underground water reservoir.