Study On Pressure Behavior And Roof Creep Characteristics Of A Fully Mechanized Mining In Gansu Province

The roof strata of mine have distinct nonlinear characteristics,and the temporal and spatial transformation of ore pressure in the process of fully mechanized mining is not clear,which needs to be further elucidated.In this thesis,the roof strata flow becomes the breakthrough point,considering the characteristics of roof strata creep and so on,aiming at the long-term unstable state of goaf roof.This thesis mainly carried out engineering geological survey,carried out physical and mechanical tests of coal rock,established the creep mechanics model of rock strata roof,and simulated the pressure developing characteristics of mining face and roof.The main conclusions are as follows.（1）Physical and mechanical parameters of coal rock are obtained.Based on geological data and critical layer theory,the goaf roof is judged and sampled.By means of the conventional uniaxial compressive test,the Brazilian splitting test,variable Angle shear test,the conventional triaxial compression test and the uniaxial creep test of the series of roof stones,the rheological analysis of the roof is prepared.（2）The creep mechanics model of roof is established.Based on the test results,Burgers constitutive model was selected to analyze the roof creep.Based on Matlab and origin drawing tool,combined with the engineering case and Burgers creep parameters,the relationship between the deflection and the time change of goaf roof under two boundary conditions of four fixed sides,three fixed sides and one free side was obtained.The characteristics of goaf roof displacement changing with time are revealed.By comparing the deflection of the four-sided fixed roof with that of the three-sided fixed roof with one simply supported roof over time,it is concluded that under the same load and time,the more boundary constraints,the better the stability of the roof.By deducing the formulas of stress and internal force under two boundary conditions and combining with the corresponding curve analysis,the rock pressure characteristics and fracture rules of goaf roof under different boundary conditions are obtained.（3）The characteristics of ore pressure in fully mechanized mining are expounded.A numerical model was established using FLAC^3D finite difference software,and Moore-Cullen criterion and Burgers criterion were selected to analyze the displacement and stress of the roof.Considering the creep characteristics of the roof,the roof stress is closer to the field monitoring data,which also reflects the rationality of using Burgers to simulate roof creep.In this thesis,the results of theoretical derivation,numerical simulation and field monitoring confirm each other,and the Burgers body creep model is adopted to be reasonable and correct.At the same time,it provides theoretical support for the safe mining of coal mines,and has important practical significance.