Research On Creep Damage Coupling Model Of Concrete Face Based On Statistical Damage Theory

As the main anti-seepage structure of concrete face rockfill dam,the concrete face is an uneven composite material composed of aggregates with different particle sizes,cementitious mortar materials and water.Its mechanical properties are very complicated.During the operation period of the concrete face rockfill dam,the concrete face will produce creep deformation due to long-term effects of various loads,which will change the mechanical properties of concrete face and threaten the safety of the entire dam.The related researches have shown that the creep deformation of concrete is closely related to the load level it bears.The main reason is that the long-term stress-deformation characteristics of concrete are the result of the interaction of external load,concrete creep and damage.Therefore,it is of great scientific significance to carry out the research on the coupling characteristics of concrete creep and damage in order to accurately grasping stress-deformation characteristics of concrete face during the operation period.The main research contents of this paper are as follows:(1)Based on the elastic creep theory and the statistical damage theory,established the concrete creep damage coupling model,deduced the calculation formula of statistical damage parameters,and compiled the UMAT material subroutine of concrete creep damage couplingmodel;Carried out The creep test of concrete under uniaxial compression with different sustained loads,and monitored the creep deformation of concrete within 30 days under sustained loads;Based on the same constraint conditions and material properties as the creep test,two groups of numerical simulation calculations of concrete with creep damage coupling and without creep damage coupling are carried out.Finally,compared the test results with the simulation results of two groups.The results show that:the calculation result considering the coupling effect of creep damage is closer to the test result,and the maximum relative error is only 6.83%.The results verified the rationality of the concrete creep damage coupling model and the applicability of the subroutine.(2)Carried out the creep damage calculation of concrete under different sustained load levels,compared and analyzed the development law of creep damage of concrete considering the coupling effect of creep damage and not considering the coupling effect of creep damage.The results show that:under the action of the lower sustained load level,the accumulation of strain energy is slow,and the internal crack of concrete is difficult to expand.At this time,the coupling phenomenon of creep and damage of concrete is not obvious,and the creep deformation behavior of concrete tends to be stable.With the increase of c sustained load level,the coupling phenomenon of creep and damage becomes more and more obvious.The interaction between creep and damage accelerates the deformation of concrete,and eventually lead to the destruction of concrete.The failure time of concrete is positively correlated with the load level.(3)Based on the subroutine of the concrete creep damage coupling model,researched he long-term stress and deformation characteristics of the concrete slab during the operation period of the rockfill dam.Compared and analyzed the deflection value,slope stress and damage value of concrete face slab in storage period,one-year after operation period,three-years after operation period and five-years after operation period.The results show that:With the sustained action of water load,the deflection value,tensile and compressive slope stress and damage of concrete face will continue to increase,but the distribution law in different periods is basically the same.In the initial stage of water storage,the growth rate of each characteristic value is faster.With the development of time,the growth rate of each characteristic value gradually slows down,and finally tends to be stable.However,the development of creep and damage of concrete is a mutually reinforcing coupling relationship.Therefore,once the damage of concrete face accumulates to a certain extent,it will also lead to the ultimate destruction of concrete face,amd threatening the safety of the whole dam.The research results of this paper can provide a new idea for the study of long-term performance of concrete face,and provide theoretical support for its durability and safety evaluation.