Mechanism of Zonal Disintegration Phenomenon (ZDP) Around Deep Roadway Under Dynamic Excavation

Due to the exhaustion of shallow resources, the underground roadway used for coal mining has reached the depth of 1000 m. The zonal disintegration phenomenon (ZDP) in deep rock mass will appear with the increase of depth which is widely different from shallow failure mode.In order to reveal the formation mechanism of ZDP, a new theoretical model is proposed. Based on the strain gradient theory and the deformation theory of plasticity, an elastoplastic damage softening model considering of dynamic excavation is put forward. The dynamic equations and boundary equations are expressed through the Runge–Kutta method. The numerical analysis of rock mass failure induced by blast loading and transient release of in-situ stress after blasting excavation is compiled by Matlab program. Taking the deep tunnel of Dingji coal mine in Huainan mine area as engineering background, the theoretical solutions of radial displacement and stresses present an oscillating mode. The theoretical values are in good agreement with the field measured results in terms of magnitude and change law. The applicability of the elastoplastic damage softening model for ZDP is confirmed and the model can be used to provide theoretical support for the deformation and failure of surrounding rock in deep underground engineering.