| The study of fatigue damage characteristics of materials has been studied for decades.However,the study on fatigue damage characteristics of rock materials has just started.The fatigue damage law of rocks under cyclic loading is not clear enough,and the theoretical system is not perfect.Based on the need of the analysis of the slope stability of the three gorges reservoir,this article is based on the national science foundation project,which is based on the fact that in chongqing,it has been studied,and it has been studied through the literature,the laboratory,the theoretical analysis,and the numerical simulation and the method systems have studied the fatigue damage characteristics of the sandstone in the cycle of the cycle;It establishes a number of factors that affect the frequency,the stress level and the fatigue life expectancy of the sandstone,and the stiffness attenuation model,and it will be applied to the analysis of the dynamics of the slope and the sensitivity analysis.It is of great significance to study the failure mechanism of rock mass under cyclic dynamic load.The main research work and results are as follows:(1)the fatigue damage test of sandstone shows that the fatigue life of sandstone increases with the decrease of upper limit stress level,which is linear with the logarithm of the upper limit stress,thus establishes the fatigue life estimation model based on s-n curve.The results show that the stress level of fatigue life is very large,and the higher the stress level,the shorter the fatigue life.Also has effect on the fatigue life of rock loading frequency,within the scope of the 1 ~ 3 hz,rock fatigue life increases with the increase of dynamic loading frequency,the fatigue life of logarithmic logarithm linear relationship with the load frequency,its essential reason is the influence of loading rate on rock strength.By considering the influence of frequency on rock strength,the correction coefficient of stress level is introduced,and the estimation model of fatigue life under multi-factor conditions is established.(2)the total stress-strain curve of sandstone is very close to the deformation of the fatigue limit,namely,the control point and the failure point are very close;In the range of 1~3Hz,the limit deformation of sandstone is basically the same,which shows that the loading frequency has less influence on the ultimate deformation of sandstone fatigue failure.(3)dynamic elastic modulus of sandstone and the cyclic loading peak stress and corresponding strain are present the attenuation law of three stages,in the case of only consider the first two stages,using regression analysis,based on fatigue damage evolution rule of residual stiffness sandstone.Combined with the characteristics of the slope engineering of the fatigue residual stiffness of rock damage model by FLAC3 D secondary development,establish a set of applicable analysis and the calculation method of fatigue damage is applied to subsequent numerical analysis.(4)the use of dynamic strength subtraction,it has two groups of random crack on a dynamic stability analysis of rock slope,the main driven load frequency,dynamic load amplitude and duration of dynamic load and dynamic carrier form four aspects,the changing rule of the dynamic stability of slope is discussed.(5)using the orthogonal design test,the four factors and three levels were selected to form 9 orthogonal design calculation schemes,and the dynamic stability and safety coefficients of each group were calculated by using FLAC3 D.Poor as indicators,through the analysis and variance analysis of sensitivity analysis results were obtained: the influence factor of dynamic load duration the highest sensitivity,the sensitivity of the influencing factors of dynamic load acceleration amplitude,the sensitivity of the dynamic load frequency slightly higher than the moving carrier. |
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