Basic Study on the Layer-crack Structure Instability of Deep Roadway Surrounding Rock and Energy Release
Author:Guo Wei Yao
Supervisor:tan yun liang zhao tong bin
As the mining depth increases,lots of field investigations have proven that layer-crack structures exsit around the roadway surrounding rock,and that layer-carck structures are related to rock bursts.Current researches about the layer-crack structure instability of roadway surrounding rock,however,are not enough.Thus,the methods of field investigation,laboratory test numerical simulation,and theoretical analysis were used for researching the formation process,deformation rule,damage characteristics,instability mechanism and energy release of layer-crack structure of roadway surrounding rock in this thesis,which is based on the careful study of typical cases of rock bursts related to layer-crack structures of brittle coal in two coal mines.At last,field practice was done.The main research contents and achievements are as follows:(1)Layer-crack structures were found before rock burst occurrence through the deep analysis of several typical rock bursts in three deep mining areas in two coal mines.Then,the damage characteristics of layer-crack structure of roadway surrounding rock were researched.Four typical failue types were got,i.e.coal cinder drop,rib heave/looseness,rib spalling and whole rib displacement.These failure types of layer-crack structure of roadway surrounding rock were quantitatively described from the two points of failue depth and damage characteristic.(2)Biaxial loading tests were done for four rock types(red sandstone,coal,gypsum and sand-gypsum)using the self-developed biaxial loading device.The strength and failure characteristics of these four rock types were got.Besides,the formation mechanism of marco-fracture surface was analyzed under different laertal pressures through the SEM test results.Then,the mechanical formation mechanism of layer-crack strcutre of roadway surrounding road was studied.(3)Uniaxial compression and brizilian split tests were done for different types of layer-crack specimens.The mechanical behavior,AE evolution characteritscs and deformation filed evolution law were got.The failure process of layer-crack body under compression condition includes three stages,i.e.compatible support,incompatible support and post-peak instable failure.The formulas used for calculating the bearing capacity of layer-crack body in the compatible support and incompatible suppor stages were derived.Then,the failure model of layer-crack body was established,and the failure mechanism was revealed.(4)Unixial cyclic loading and unloading tests were done for differernt layer-crack specimens.The mechanical behavior and AE evolution characteristics were got.The energy and damage evolution laws of layer-crack body during its deformation failure process were researched.Then,the influences of homogeneity,element strength and critical energy dissipation value on the energy dissipation of layer-crack body were analyzed.(5)Based on the combination charactertistics of layer-crack structure of roadway surrounding rock,the failure process and energy evolution law of "coal body" and "coal body+roof" combination structures were researched through layboratory test and numerical simulation.Two types of instable failure model for the layer-crack strucutere of roadway surrounding rock were established.In addition,the method for calculating burst energy was given.Then,the engery criterion of burst instability was proposed.The dynamic instability mechancism of layer-crack structure of roadway surrounding rock was revealed.At last,the question "energy release for dynamic instability of layer-crack structure of roadway surrounding rock"was answered.(6)Control concenpts for dynamic instability of layer-crack strcutre of roadway surrounding rock were proposed based on the four stages of its failure process.From the two aspects,including increasing the engeryg used for the failure of layer-crack coal and decreasing the engery released from the intact coal and roof,the related control methods were given.