Research On The Influence Of Permeable Paving Material’s Porosity Characteristics On Its Permeability

With the accelerated development of urbanization in my country,there are more and more hardened roofs and hardened pavements in cities.As a result,a large amount of rainwater cannot penetrate into the ground during the raining process,which not only easily forms road runoff,but also affects the circulation of rainwater under natural conditions.Cause damage.To solve this problem,the construction of sponge cities with the design concept of "seepage,retention,storage,purification,use,and drainage" will be a development trend.On the other hand,the process of recycling construction waste in my country needs to be promoted.The problem of large output of construction waste but insufficient utilization has gradually affected the harmonious living environment,and the treatment and recycling of construction waste is imperative.Recycled brick-concrete aggregate has the characteristics of high water absorption.It can be used as a permeable paving material in the construction of sponge cities.It can absorb water under the condition of ensuring a certain water permeability.It can hold rainwater for the ground structure and promote natural rainwater circulation.Significance.This project starts with the seepage characteristics of recycled materials and the seepage behavior of permeable pavement facilities,and experimentally studies the effects of aggregate types,particle size and other factors on the void characteristics and seepage performance of the recycled material structure layer,and establishes the parameters of the recycled materials.And the prediction model of the structural layer infiltration performance index;the existing rainfall permeation model of the class III pavement is revised into a rainfall infiltration model suitable for recycled brick-concrete aggregates,and the model is used to design the working conditions of different structural layers The simulation and comparison of the material’s seepage behavior provide a reference for the design of sponge city permeable paving materials.The main conclusions of this paper are as follows:(1)The impregnation performance of recycled graded crushed stone materials is measured,and the test puts forward the impregnation performance index that can characterize the different void characteristics of the material.Among them,the volumetric adsorption rate can represent the proportion of the volume of some water-absorbing pores and some small water-storing pores in the rain infiltration stage,and the volume retention rate can represent the proportion of the volume of the small water-storing pores and the large water-permeable pores during the rainfall process,and the volumetric water storage rate It can be used to characterize the volume ratio of particle water absorption holes and small water storage gaps after rainfall.(2)The effects of aggregate particle characteristics and structural layer filler characteristics on the material’s impregnation performance were studied through the impregnation test.Among them,the filler characteristics of the structural layer have a small effect on the impregnation performance,and the aggregate particle characteristics have a greater effect.The smaller the particle size of the recycled aggregate,the stronger the water storage capacity.The volumetric water storage rate of recycled sand can reach about 26%,which is 1.8～2.6 times that of recycled coarse aggregate;The storage performance has a greater impact.The water storage performance of the material increases with the increase in the volume of the reclaimed sand layer.The content of the recycled aggregate and the volume water storage rate of the material have a linear relationship.Changing the structural layer thickness and other factors to study the material’s impregnation performance index,it is found that the volumetric water storage rate is an index that can characterize the material’s impregnation characteristic.(3)Establish the relationship between material parameters and volumetric water storage rate through two methods of superposition principle and BP neural network model,and form a prediction model for the permeability and storage characteristics of recycled graded gravel layer materials.The accuracy of the model reaches 88.8%..Based on the experimental research results,the parameters of the existing type Ⅲ permeable pavement rainfall permeation model were revised,and the water adhesion rate parameter in the original model was revised to the volume storage rate parameter,and a rainfall infiltration model suitable for recycled aggregates was established.(4)According to the prediction model of the material seepage characteristic index of recycled graded crushed stone layer,design the void structure parameters and seepage characteristic index of different working conditions,and compare and evaluate the seepage behavior of the graded gravel material layer of permeable pavement under different working conditions.The results show that adding recycled aggregate or using multi-grain mixed fillers is an effective means to improve the seepage effect of the graded crushed stone layer.Increasing the amount of recycled aggregate can not only ensure the water permeability of the structural layer,but also Improving the retention capacity of structural layer materials after rainfall is of greater significance to alleviating soil and water damage and promoting rainwater circulation.