The Mechanism Study of Cracks Propagation of Different Floor Strata Combinations Under Mining

Abstract

To obtain the water resistance performance of floor strata under different rock layers and fracture combination, the two cracks’ propagation path under different situations was given by using minimum plastic zone theory according to the change of the fracture factor and the plastic strain of different strata combination cracks under the influence of fault, water pressure and mining. The shortest distance of the rock bridge between the two cracks after bursting in different strata combination was obtained. And the water resistance performance of every strata combination was analyzed. The conclusion was that the water resistance performance of the floor strata under the 3214 combination of soft–soft–hard–hard was the worst. While the 1243 combination of soft rock, hard rock, soft rock, hard rock was the best. The fracture factor combination and the plastic strain of the crack would reach maximum under mining condition. And the crack was mostly easy to destroy. The distance of the rock bridge between the two cracks after bursting was the shortest under the 3214 combination of soft–soft–hard–hard strata. The distance of the rock bridge between the two cracks after bursting was the longest under the 1243 combination of soft rock, hard rock, soft rock, hard rock strata. And the distance of the rock bridge between the two cracks after bursting would be shorten when considering the water pressure inside the crack and fault, which resulted in the decrease of rock water resistance performance.