Height of the Water-Flowing Fractured Zone of the Jurassic Coal Seam in Northwestern China

摘要

Research on the height of the water-flowing fractured zone (HWFFZ) is important for mine safety and regional eco-environmental conservation in the Jurassic coal field of northwestern China. Using the Cuimu coal mine as a case study, on-site measurement, mechanical theory calculation, and numerical simulation were used to analyze the regularity of the HWFFZ in this area. A television borehole wall imaging system with a light source allowed us to examine the size and shape of fissures intuitively, allowing the top boundary of the HWFFZ to be determined. Per mechanical theory, the overlying strata in the decreasing stress zone was simplified as a clamped rectangular plate and the formula for calculating HWFFZ was obtained by comparing the value of the ultimate deflection of the thin plate and the height of the free space in the lower part of the stratum. In addition, the dynamic development of the HWFFZ was simulated using realistic failure process analysis software. The unusual characteristics of the HWFFZ were analyzed from two aspects: the inapplicability of the traditional empirical formula and the difference of the overlying strata structure of the Jurassic and the Carboniferous Permian coalfields. These strata can be divided into layered and integrated strata in the Jurassic coalfield.