| The ingate is located at the throat of the mine,with large section,complex structure and long service life.During the construction process,the surrounding rock is repeatedly disturbed by the construction,resulting in the deformation and damage of the shaft wall of ingate and its upper and lower connecting sections,which seriously threatens the production safety of the mine.Taking the ingate of the west air shaft of Yuandian No.2 coal mine as the engineering background,this paper carries out the research on the temporal and spatial evolution law of the surrounding rock stress field and the diachronic stability of the surrounding rock during the construction of the ingate of the coal mine shaft by using the methods of indoor test,theoretical analysis,similar model test and numerical simulation,in order to provide theoretical support for the scientific design,safe construction and operation of the ingate of the coal mine shaft in the future.The main research work and achievements of this paper are as follows:(1)Through the indoor physical and mechanical test and conventional triaxial compression test of siltstone,the strength parameters such as peak strength,elastic modulus,cohesion and internal friction angle under different stress states are obtained,which reveals the energy evolution and deformation failure mechanism of siltstone in conventional triaxial compression test.(2)Based on the actual adjustment path of stress in the process of roadway surrounding rock excavation,the test loading mode is set,and the creep test of siltstone under different initial confining pressures is carried out.The creep characteristics of siltstone under different confining pressures are systematically analyzed.The test results show that when the stress level is lower than the long-term strength of siltstone,its creep only shows two creep stages: attenuation and steady-state,and the steady-state creep rate is close to 0;With the gradual removal of confining pressure,the steady-state creep rate gradually increases to a constant greater than 0;When the stress level is higher than its quasi failure stress,the specimen enters the stage of nonlinear accelerated creep and creep failure occurs;The long-term strength of siltstone under three different initial confining pressures is about 70% of its corresponding creep failure strength.(3)Based on the generalized Kelvin model and the fractional order theory,a fractional order viscoelastic plastic creep model which can describe the whole process creep characteristics of siltstone is constructed by introducing the fractional order visco-plastic body with yield limit.According to the correlation flow law,the model is extended to three-dimensional stress state,and a simple and easy parameter identification method is proposed.The model parameters are identified according to the triaxial compression graded unloading creep test curve of siltstone,and the rationality of the model is verified by comparison with Nishihara model and deviation analysis.(4)The three-dimensional similar model test research on the stress response law of surrounding rock during the construction of ingate in coal mine shaft is carried out.The results show that the shallow surrounding rock below the bottom plate of ingate is subjected to tensile stress,the deep surrounding rock is subjected to compressive stress,and the surrounding rock above the top plate of ingate is subjected to compressive stress;The stress of the surrounding rock of the roof and floor of ingate roadway is gradually released during the excavation and support of the vertical shaft and ingate roadway,and the stress release in the surrounding rock of the floor is more obvious.When the stress reduction of the surrounding rock of the floor reaches the load imposed by the upper oil cylinder,it gradually tends to be stable,and the stress release rate of the surrounding rock of the roof is about 25% ～ 40%.(5)The customization process of fractional viscoelastic plastic creep model in FLAC 3D is studied,and the three-dimensional finite difference form of fractional viscoelastic plastic creep model is derived.Based on Visual Studio 2010 platform,the customized creep model is compiled with C + + language,and the dynamic link library file(.DLL)is generated and embedded into the large-scale finite difference software FLAC 3D to complete the secondary development of fractional viscoelastic plastic creep model.Finally,the accuracy of secondary development is verified by an example of triaxial compression graded unloading creep.(6)Taking the ingate of the west air shaft of Yuandian No.2 coal mine as the engineering prototype,the three-dimensional numerical calculation model of the ingate of the coal mine shaft considering the creep effect is established by using FLAC 3D software,and the fractional viscoelastic plastic creep model of siltstone is used for calculation.The diachronic stability of the surrounding rock of the ingate of the coal mine shaft is analyzed,and the displacement field,stress field and plastic zone distribution of the surrounding rock of the ingate are revealed.The numerical calculation shows that the reasonable time of secondary support is about 35 days after the completion of excavation.(7)This paper puts forward the evaluation method of the stability of the surrounding rock of ingate in coal mine shaft.That is,the Lambe stress path method and the principal stress space method are used to analyze the two-dimensional and three-dimensional stress redistribution paths of surrounding rock respectively.According to the two-dimensional and three-dimensional stress redistribution paths of surrounding rock,the two-dimensional and three-dimensional safety factors are established respectively,and then the stability of surrounding rock of ingate is evaluated.Fig.[139] Table [34] Reference [178]... |
PDF Full Text Request