Fracture mechanics solution of confined water progressive intrusion height of mining fracture floor

In order to obtain the value of confined water progressive intrusion height of mining fracture floor, the analysis equation was deduced based on the fracture extension theory of the fracture mechanics. Furthermore, the influence of some parameters (e.g., advancing distance of working face, water pressure, initial fracture length and its angle) on confined water progressive intrusion height were analyzed. The results indicate that tension-shearing fracture of floor is extended more easily than compression-shearing fracture under the same conditions. When floor fracture dip angle is less than 90°, tension-shearing extension occurs more easily on the left edge of the goaf. If fracture dip angle is larger than 90°, it occurs more easily on the right edge of the goaf. The longer the advancing distance of working face is, the greater initial fracture length goes; or the larger water pressure is, the greater possibility of tension-shearing extension occurs. The confined water progressive intrusion height reaches the maximum on the edge of the goaf. Field in situ test is consistent with the theoretical analysis result.