Study On Attenuation Of Dynamic Elastic Modulus Of Concrete Under Wind-sand Environment

The northwest region of China belongs to the Sandstorm region of Central Asia.Sandstorm disasters occur frequently.The concrete structures such as houses,roads and Bridges in the northwest region suffer from sandstorm erosion for a long time,which will bring severe tests to the safety and durability of these concrete structures.It is of great significance to study the wind-sand pressure,wind-erosion damage law and wind-erosion mechanism of concrete structures under the action of wind-sand to ensure the safe service of concrete structures under the environment of wind sand.Under the action of aeolian sand,the impact of sand particles on concrete makes the cement mortar on the concrete surface crack,the surface material spalling,and the elastic modulus of the material decreases accordingly.Under the action of continuous wind-sand,the continuous impact of sand particles makes the cracks gradually expand and extend,and the elastic modulus of the surface also decreases continuously,which is the process of wind erosion.Therefore,in order to analyze the mechanism of wind erosion of concrete,it is necessary to deeply study the attenuation of dynamic elastic modulus of concrete under the action of wind-sand,establish attenuation model,which can provide reference for the durability design of concrete structures in sand-dust frequent areas.The main research contents of this paper are as follows:(1)Conduct numerical simulation on the impact process of sand particles on concrete under the action of wind-sand,and analyze the impact times of sand particles on concrete surface and the change of wind-sand pressure on concrete surface under different aeolian sand action time,different sand transport rates,different sand velocity and different particle sizes.(2)The wind erosion test of concrete under the action of wind sand was carried out,and the mass loss rate and the relative dynamic elastic modulus were selected as the test contents to represent the quality loss degree of concrete and the attenuation degree of dynamic elastic modulus respectively.The mass loss and dynamic elastic modulus attenuation of concrete under different sand velocity,transport rate and particle size were analyzed.The results show that the mass loss of concrete test block increases with the increase of wind speed,sand transport rate and particle size when the action time of wind-sand is constant.The relative dynamic elastic modulus of concrete test block decreases exponentially with the cumulative time of aeolian sand.(3)The relationship between dynamic elastic modulus of concrete and impact times of sand particles is established.On the basis of concrete wind erosion test and numerical simulation,the attenuation model of dynamic elastic modulus of concrete is established,and the relationship between the number of sand impact and the parameters of sand flow is established,and then the relationship between the number of sand impact and the dynamic elastic modulus of concrete under the action of wind-sand is obtained.The dynamic elastic modulus of concrete decays exponentially with the increase of the number of sand impacts,so the wind erosion process of concrete can be analyzed,which indicates that the wind erosion of concrete is the result of repeated sand particles impacts.(4)Based on weibull distribution theory,wind erosion life prediction of concrete is carried out,the dynamic elastic modulus is selected to measure the damage degree of concrete,and the prediction model of concrete wind erosion life under the action of wind sand is established,and then the critical aeolian action time of concrete specimen damage failure is calculated under different wind speed,sand transport rate and particle size.Introduce similitude theory,on the basis of the life of concrete test block calculated by wind erosion test,the service life of concrete structures in the actual wind-sand environment is deduced,and the damage failure life of concrete structures with the change of wind speed,sand transport rate and particle size is obtained,and the life prediction model of concrete structures in the actual environment is established.