| With the gradual transfer of coal resources to deep mining,the complex environment of "three heights and one disturbance" in deep roadway causes the surrounding rock to present nonlinear large deformation phenomena such as large deformation amount,fast deformation rate,long duration,strong destructive force,and serious damage of support body.Roadway maintenance is extremely difficult,and it is difficult to ensure roadway stability by adopting conventional support forms.By studying the mechanical properties and energy evolution analysis methods of rock mass under compression and loading and unloading conditions,based on the energy evolution analysis ideas under rock loading and unloading and compression conditions,this paper explores the analysis methods of energy evolution and aging characteristics of rock mass,and builds a creep damage constitutive model based on energy dissipation.The engineering background is Gaojiejie Mountain in mining area 81 of Xinhu Coal Mine.By using the methods of laboratory test,theoretical analysis,numerical simulation and field industrial test,the damage and deterioration aging characteristics and instability mechanism of the surrounding rock of high-stress roadway are studied,aiming to provide scientific basis for the support of high-stress roadway.Specific conclusions are as follows:(1)Based on the assumption that a small amount of cyclic loading and unloading has little effect on the elastic properties of rock,that is,the elastic properties of uniaxial or triaxial graded loading and unloading are equal to the elastic properties of corresponding compression tests,the correctness of the hypothesis is verified by loading and unloading tests;Through analysis,it is found that uniaxial compression test,conventional triaxial compression test and true triaxial compression test all obey the linear energy storage law.A calculation method of energy evolution under rock compression is proposed based on the linear energy storage law combined with loading and unloading test.The phenomenon that the increase of principal stress in one direction induces the change of energy in other principal stress directions is defined as induced energy,which can be divided into induced elastic energy and induced dissipation energy according to whether it is reversible or not.Rock confining pressure and medium and small principal stress not only improve the energy storage limit of rock,but also affect the energy proportion of rock during loading.The greater the intermediate or minimum principal stress is,the more elastic energy is stored in rock,and the greater the proportion of elastic energy to input energy is.(2)The residual strain of the uniaxial cyclic loading and unloading of the rock gradually decreases until no residual deformation occurs,the nonlinear characteristics of the rock appear as elastomers,and the occurrence times of nonlinear pseudo-elastomers are inversely proportional to the upper limit value of the cycle,and the nonlinear pseudo-elastomers continue to bear the loading and unloading effect after the nonlinear pseudo-elastomer features appear,or the upper limit of the loading and unloading of the nonlinear pseudo-elastomers disappear.Under the same unloading stress path,the higher the unloading rate,the higher the input energy density and the dissipated energy density,but the unloading rate has no effect on the induced elastic energy.The true triaxial unloading stress path has an effect on induced input energy,elastic energy and dissipative energy of rock mass,that is,the induced elastic energy density and dissipative energy density of rock mass that first unloads the intermediate principal stress are higher than that of the first unloading minimum principal stress test.In addition,the larger the induced dissipation energy is,the more easily the rock is destroyed,and the larger the induced elastic energy is,the more severe the rock failure and the smaller the fragmentation degree.A method for calculating rock energy under true triaxial unloading under different stress paths is proposed,which provides a theoretical basis for studying the energy evolution of rock mass under deep complex stress paths.(3)Based on the fact that a small amount of loading and unloading has no effect on the elastic energy of rock mass,a creep loading and unloading test is proposed to analyze the energy during the creep process of rock mass,which provides a new method for the evolution analysis of the creep energy of rock mass.It is found that the growth rate of dissipative energy density decreases with the increase of time in the decay creep stage,the dissipative energy density increases linearly with the increase of time in the constant creep stage,and the dissipative energy density increases with the increase of time in the acceleration creep stage.In the process of uniaxial and triaxial creep of rock mass,the density of elastic energy stored in rock gradually decreases under the action of time effect.It is found that there is a linear relationship between time and elastic energy,which is defined as the linear decay law of elastic energy.Based on the linear dissipation law of rock mass creep,it can be considered that the internal elastic energy of rock in the creep process increases with time and is transformed into dissipative energy.Therefore,it can be considered that the creep process of rock is not only a process of energy dissipation,but also a process of energy conversion.(4)Based on thermodynamics,rheological theory and damage mechanics,a coupled viscoelastic-plastic damage constitutive model of rock was established,the uniaxial creep constitutive equation was obtained by Laplace transform,and the creep model parameters at all levels of the uniaxial fractional creep test were fitted by the rheological curve decomposition method,and the correctness of the constitutive model was verified by comparing with the test data.A three-dimensional viscoelastic-plastic coupled constitutive equation based on energy dissipation is proposed by Laplace transform and elastic theory.The parameters of the constitutive model are identified by the rheological curve decomposition method,and the constitutive model is verified by the theoretical and experimental curves.(5)Based on the coupled viscoelastic-plastic damage constitutive model of rock,the displacement expression of surrounding rock is obtained by Laplace inverse transformation,and the criterion of entry accelerated creep of high-stress roadway is constructed.Through field measurement,theoretical analysis and equivalent theory,the radius of the elastic-plastic zone of the surrounding rock is determined.Based on the geological parameters of Xinhu Coal mine,the primary support scheme was determined by numerical simulation.Combined with the primary support parameters,Flac3 D was used to analyze the deformation at the constant creep stage,combined with the numerical simulation,the secondary support scheme was proposed,combined with the field measurement to verify the feasibility of the support scheme,providing a certain theoretical basis for the support research of high-stress roadway surrounding rock.Figure 144 Table 22 Reference 195... |
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