Research On Materials And Structures Of Mountain Sponge City Permeable Aspalt Pavement

Permeable asphalt pavement has a larger porosity,which can play the role of water seepage,storage and drainage,and is conducive to solving the problems of increasing urban heat island effect,falling groundwater levels,frequent waterlogging during heavy rains,water shortage and serious noise pollution,which is consistent with the construction concept of sponge cities.Due to the characteristics of larger longitudinal slopes and heavy rainfall in mountain cities,the permeability of permeable asphalt pavements is different from that of plain cities,and the relevant materials and structural designs will also differ.This paper uses a combination of theoretical analysis and laboratory tests to systematically study the material design,bearing capacity,and permeable capacity of each structural layer of a permeable mountain sponge urban asphalt pavement,then recommended type of the typical full section permeable asphalt pavement structure of the mountain sponge city is proposed.The characteristics of heavy rain in Chongqing were investigated.The permeation rate of permeable asphalt pavement under different heavy rain intensity,longitudinal slope and porosity was studied by using a self-made rainfall simulation device.The influence of various factors on the permeation rate was analyzed,and a model for predicting the relationship between slope rate and longitudinal slope,porosity and storm intensity was established.The results show that the permeation rate decreases with the increase of the longitudinal slope and the intensity of the rainstorm,and increases with the increase of the porosity.At the same time,when the longitudinal slope increases under the same porosity,the permeation rate of the permeable asphalt pavement under the same rainfall intensity tend to be consistent,and the influence of the rainstorm intensity on the permeation rate gradually becomes lower.The influence degree of each factor on the permeability rate from high to low is longitudinal slope,porosity and rainstorm intensity.Based on the research results of the permeation rate of the permeable asphalt pavement in the mountain sponge city,the bearing capacity and permeability of the permeable asphalt pavement were comprehensively considered,and the reasonable permeation rate and target porosity of the permeable asphalt pavement in the mountain sponge city were determined,and the mix design of the permeable asphalt mixture was carried out.Based on the mix design results,grade B and grade E are selected for road performance and permeability tests.,and the test results meet the requirements.Under the premise of bearing capacity and considering permeability,the base of the mountain sponge urban permeable asphalt pavement is designed as a semi-rigid base.Cement-treated permeable base is selected as the base and water storage material.Sand,silt and clay were used as soil-based materials,their permeability and strength characteristics have been studied.The results show that grade G can be used as a design grade for cement-treated permeable base and subbase.The optimal cement dosage of base and subbase are 7% and 5%,and their compressive strength and permeability meet the design index requirements.The load bearing capacity can reach more than 70%before saturation while sand is saturated with water,and the strength loss is minimal.At the same time,its permeability coefficient is much higher than silt and clay.It has good permeability and is an ideal subgrade of mountain sponge urban permeable asphalt pavement.According to the research on the permeable asphalt pavement structure of the mountain sponge city,the mechanical response analysis of the pavement structure under different parameters was carried out with the help of Abaqus finite element software.The pavement structure was verified using the APAD asphalt structure analysis software.Based on the climate,topography,and geological conditions of Chongqing,recommended type of typical full section permeable asphalt pavement structure for mountain sponge cities in urban main,secondary and branch roads was proposed to provide a reference for the construction of mountain sponge city.In addition,when designing a mountain sponge urban permeable asphalt pavement,the bearing capacity overall structure of the pavement structure can be improved by increasing the combined thickness of the base and the sungrade,appropriately reducing the amount of cement used in the base and the sungrade,and using a soil base with a higher modulus.