Butterfly leaf type roof falling mechanism and control technology of mining gateway

LI Ji; MA Nianjie; ZHAO Zhiqiang

doi:10.13199/j.cnki.cst.2017.12.009

Abstract：According to the stress environment and surrounding rock condition complicated in the mining gateway,when the roof falling mechanism of the available gateway was not suitable applied to explain the roof falling mechanism of the mining gateway,based on the conveying gateway of No.81305 coal mining face in Baode Mine as the engineering background,the theoretical analysis,numerical simulation and site test and other method were applied to study the formation mechanism of the butterfly leaf shaped plastic zone in the surrounding rock of the mining gateway and the evolution law of the butterfly leaf shaped plastic zone in the mining gateway.Based on the circumstances,the paper revealed the butterfly leaf shaped roof falling mechanism of the mining gateway.The study showed that due to the butterfly leaf,the four butterfly leaf at the butterfly leaf shaped boundary of the plastic zone in the round type mining gateway with homogenous rocks would cause the degradation and disappearance,deflection and expansion and then would form the butterfly leaf shaped plastic zone.The butterfly leaf size in the butterfly leaf shaped plastic zone were mainly affected by the side pressure coefficient,the cohesion force of the surrounding rock,internal friction angle and the radius of the gateway.When the butterfly leaf of the butterfly leaf shaped plastic zone was located above the roof,the plastic failure strata within the butterfly leaf would cause serious deformation.When the extension value of the anchor could not suit the large deformation of the roof,the anchor cable would be broken and thus the support failure occurred,the plastic zone would cause a serious extension and the roof falling accident would be occurred.Based on the butterfly leaf shaped roof falling mechanism of the mining gateway,a bolt extended length and anchor coordinated support technology as well as the extended length bolt and conventional bolt coordinated support technology were provided and the technology was applied to the industrial trial of the conveying gateway in No.81305 coal mining face.During the mining period of the coal mining face,the broken rate of the anchor was reduced from 64.5％ to 12.5％ and the roof falling accident occurred was precluded.