Analysis Of Void Structure And Numerical Simulation Of Mechanical Properties Of Pervious Concrete

Pervious concrete is an essential pavement material in sponge city construction,There are a large number of pores in the road surface so that the water can flow into the soil to supplement the groundwater resources.many scholars have done a lot of research on the macroscopic physical and mechanical properties of pervious concrete,and many analysis results show that:the internal distribution of a large number of irregular voids has a great effects on the material properties.In order to analyze the influence of pore structure characteristics on pervious concrete.In this paper,the performance of pervious concrete is studied by means of laboratory test and numerical simulation,first of all to aggregate size and porosity as main variables to analyze its physical and mechanical properties,and the second section through the pervious concrete image analysis of void characteristics,finally,the random pore finite element models were established according to the pore characteristics and the mechanical properties of the two-dimensional model of pervious concrete were studied.related research results are as follows:(1)Cubic specimens with G1 and G2 gradation and 100 side length were prepared with different design void ratio as variables.the specimens were used to analyze compressive strength test and porosity measurement test.The compressive test data show that the compressive strength of the specimen with the same aggregate particle size decreases with the increase of porosity,and when the porosity is the same,the compressive strength of the specimen increases with the increase of aggregate particle size.The porosity test shows that there is a quadratic term relationship between the effective porosity and porosity of the specimen,and the larger the aggregate particle size is,the larger the ratio of effective porosity to total porosity is.(2)After longitudinal cutting and grinding of permeable concrete specimens,the area and shape characteristics of plane pores are analyzed by means of PHOTOSHOP,IMAGE PRO PLUS,MINITAB and other software.Firstly,it is found that there is a high linear correlation between the plane porosity and the porosity of the specimen by analyzing the characteristics of the area.Secondly,two parameters,equivalent diameter and roundness,are introduced to characterize the shape characteristics of pores,and the effects of porosity and aggregate particle size on the shape characteristics are discussed.the results show that the larger the aggregate particle size is,the larger the average equivalent diameter of pores is.However,the change of porosity has little effect on the average equivalent diameter,while the aggregate particle size and porosity have little effect on the roundness of the plane pores,and the average roundness changes about 2,indicating that the long axis of the pore is approximately twice as much as the short axis.(3)According to the above analysis,two parameters of plane pore area size and shape characteristics are obtained.the finite element software ANSYS was used to establish the circular and oval two-dimensional random void finite element models with different porosity,and the simulation results showed that the greater the porosity was,the greater the attenuation of the comprehensive modulus of the specimen would be.With the same porosity,the attenuation of modulus is also different for different void shapes.The attenuation of modulus for oval void is greater.With the increase of model porosity,the stress concentration area around the voids in the specimens with high porosity is wider under the same load.The vertical displacement of the specimen decreases gradually from top to bottom under load.Under the same void shape,the vertical displacement of the specimen increases with the increase of porosity,and the vertical displacement of the oval porosity specimen is larger than that of the circular porosity specimen.