Study On Damage Constitutive Model Of Rock Based On Three Dimensional Griffith Strength Criterion

In geotechnical engineering,most rock materials are under complex and variable stress conditions and exhibit significant non-linear mechanical properties.In order to ensure the stability and safety of geotechnical engineering,it is important to study the deformation processes and damage mechanisms of rocks under different stress conditions and to establish mature and applicable rock damage intrinsic structure models and damage evolution models.In view of this,this paper interconnects fine-scale damage mechanics,statistical probability and continuous medium damage mechanics theories,adopts the three-dimensional Griffith strength criterion as a new criterion for measuring the strength of rock microelements,assumes that the rock microelements strength distribution obeys the two-parameter Weibull probability function,introduces damage correction coefficients,establishes a rock damage evolution model and a statistical damage intrinsic model applicable to uniaxial,triaxial and various other complex stress fields,and uses the regression method and the peak point method to determine the values of the distribution parameters.On this basis,the deformation pattern and strength characteristics of rocks under different stress conditions were analysed by means of measured data from uniaxial compression,uniaxial cyclic addition-unloading and conventional triaxial compression tests,and the connection between the damage variable D and strain and stress in rocks was discussed,verifying the validity and correctness of the theoretical statistical damage model at each stage of the test curve.In addition,sensitivity analyses and studies on the effects of the distribution parameters and damage correction coefficients on the shape of the present structural model curve are carried out for two working conditions of uniaxial cyclic addition-unloading and triaxial compression of the rock,and the mathematical and physical significance of the distribution parameters is clarified.Finally,the distribution parameters are reasonably corrected based on the law between the distribution parameters and the peak strain and surrounding pressure.The results of the study show that.(1)The damage of rock materials is gradually accumulated and unrecoverable,and its macroscopic damage is caused by damage accumulation.(2)Under the condition of uniaxial compression of rock,the statistical damage constitutive model is in good agreement with the experimental data as a whole,and further research is carried out under uniaxial cyclic loading and unloading.The results show that the correlation coefficient R~2between the loading and unloading theoretical curves and the experimental data of each grade is above 0.98913,which proves the rationality and reliability of the constitutive model.(3)Under the triaxial compression conditions with different circumferential pressures,the correlation coefficient R~2between the theoretical curves of the damage principal structure model and the experimental curves was found to be above 0.9375,which indicates that the principal structure model is applicable to the engineering conditions under the action of triaxial stress.(4)Through the study of the parameters of the principal structure model under uniaxial cyclic loading-unloading and triaxial compression conditions of the rock,it is found that the distribution parameters reflect the deformation characteristics of the rock,and the magnitude of its value has a direct influence on the change of the shape of the theoretical curve.(5)Damage correction coefficient is introduced intoα,so that the derived statistical damage intrinsic model of rock is more consistent with the real rock damage law.The anisotropy and inhomogeneity of the rock material and the residual strength of the rock after damage are better reflected.(6)By combining damage mechanics with fracture strength theory,the statistical damage constitutive model of rock based on three-dimensional Griffith criterion has the advantages of simple parameter form,clear physical meaning and more consistent with the actual situation of engineering.It provides a new perspective for the study of damage evolution and damage constitutive model of rock materials.Figure[forty-one]Table[four]Reference[eighty-five]...