Simulation Study On Static And Dynamic Mechanical Properties Of Dry And Saturated Concrete

Many concrete structures have long served in water environments and reach saturation under water confining pressure.Compared with dry concrete,the mechanical properties of saturated concrete will undergo significant changes.Hydraulic concrete structures may be subjected to dynamic loads such as earthquakes and impacts during service.Conducting simulation research on the static and dynamic mechanical properties of dry and saturated concrete under different stress states is of great significance for the reliability and safety of hydraulic concrete structures during load service.Therefore,this article conducts simulation research on the static and dynamic mechanical properties of dry and saturated concrete under uniaxial compression,uniaxial tension,biaxial compression,and biaxial tension compression stress states.（1）In this thesis,concrete is regarded as a four phase composite material composed of aggregate,mortar,pores and interface layer.Based on the Monte Carlo method and the Wallace formula,a two-dimensional random aggregate model of concrete is generated using MATLAB.Then,a plastic damage model was used to describe the mechanical behavior of mortar and interface layer.Based on this,pore water was characterized,and the rate effect of various materials in concrete under dynamic strain rate and the viscous effect generated by pore water were considered.Finally,numerical models of dry and saturated concrete were constructed and validated.（2）A simulation study was conducted on the uniaxial compressive and uniaxial tensile properties of dry and saturated concrete with different porosity（1%,2%,3%,4%）and different strain rates(10^-5s^-1,10^-4s^-1,10^-3s^-1,10^-2s^-1).The effects of porosity and strain rate on the peak stress,elastic modulus,stress-strain curve,and failure morphology of the two types of concrete were compared and analyzed.The results indicate that the uniaxial compressive and tensile strength of dry and saturated concrete decreases continuously with the increase of porosity,and increases continuously with the increase of strain rate.Among them,the compressive and tensile strength of saturated concrete shows higher rate sensitivity.Under uniaxial compressive load,the damage zone develops diagonally in the triangular area at the top and bottom of the concrete model,ultimately presenting a"hourglass"shaped failure pattern.The uniaxial tensile failure mode of concrete under different strain rates shows fracture failure.（3）A simulation study was conducted on the biaxial compressive performance of dry and saturated concrete under different lateral compressive stresses（0MPa,4MPa,8MPa,12MPa）and different strain rates(10^-5s^-1,10^-4s^-1,10^-3s^-1,10^-2s^-1).Analyzed the effects of lateral compressive stress and strain rate on the biaxial compressive strength,elastic modulus,stress-strain curve,and failure mode of two types of concrete.The results indicate that both strain rate and lateral compressive stress can improve the biaxial compressive strength and elastic modulus of concrete.As the lateral compressive stress increases,the sensitivity of the biaxial compressive strength rate of concrete gradually decreases;As the strain rate increases,the effect of lateral compressive stress on the biaxial compressive strength of concrete gradually weakens.The stress-strain curve of concrete shows an outward expansion trend with the increase of strain rate.As the lateral compressive stress increases,the number of damage zones in concrete increases significantly,and the area of the damage area gradually increases.（4）A simulation study was conducted on the biaxial tensile and compressive properties of dry and saturated concrete under different lateral tensile stresses（0MPa,0.3MPa,0.6MPa,0.9MPa,1.2MPa）and different strain rates(10^-5s^-1,10^-4s^-1,10^-3s^-1,10^-2s^-1).The effects of lateral tensile stress and strain rate on the biaxial tensile and compressive strength,peak strain,stress-strain curves,and failure modes of two types of concrete were analyzed.The results indicate that as the strain rate increases,the biaxial tensile and compressive strength and peak strain of the two types of concrete gradually increase,with saturated concrete being more sensitive to strength rate.As the lateral tensile stress increases,the biaxial tensile and compressive strength and peak strain of concrete show a phased downward trend.The stress-strain curve gradually converges inward with the increase of lateral tensile stress.The greater the lateral tensile stress,the more obvious the brittle characteristics of concrete.Under the action of high lateral tensile stress,the biaxial tensile and compressive failure mode of concrete shows tensile failure.