Optimization Of Anti-clogging Performance Of Pervious Pavement Structure

Pervious concrete pavement structure is a kind of environmentally friendly and ecological pavement material with high permeability.It can effectively mitigate the negative effects brought by urbanization development such as urban floods,noise,urban heat island effect etc.Permeability is one of the important indicators for the structure to maintain the above functions,but its pores are easy to be clogged,which leads to the significant decreased of permeability and other functions,and finally the pervious concrete pavement is completely ineffective.So,it is very necessary to improve the anti-clogging performance of pervious concrete pavement.In this study,six models were established based on the three influencing factors of single-double pervious structure,different top aggregate particle size and top layer thickness.The influences of these three factors on the anti-clogging performance of pervious concrete structures were observed by Computational Fluid Dynamics(CFD)and Discrete Element Method(DEM)numerical evaluation.In addition,based on the above analysis,a new tubular permeable structure is proposed in this paper,and 9 different structural models are established.The anti-clogging performance and compressive strength of the structure are studied by numerical simulation and laboratory experiments.Based on the research of other scholars,we know that in the double-layer pervious concrete structure,the selection of top aggregate particle size is extremely important for the anti-clogging performance.Based on the theory of Taisha-based filter layer and the shielding effect of top layer,two possibilities are proposed.First,if the local sediment particle size is small,based on the theory of Taisha-based filter layer,we can maximize the particle transportation capacity of pervious concrete structure,and use relatively large particle size as top aggregate particles;Secondly,if the local sediment particle size is large,based on the shielding effect of the top layer,we can maximize the shielding effect by using relatively small particle size as top aggregate particles.Based on the study of top aggregate particle size and top layer thickness,different pavement structure models were built to analyze the effects of different pervious structures,top layer thicknesses and top aggregate gradations on the anti-clogging performance.Compared with the single-layer pervious structure,the double-layer pervious structure has an excellent shielding effect,which the types and quantity of sediment particles that can enter the pores and the clogging depth of the double-layer pervious structure are reduced.The research results show that the most serious clogging area of the double-layer pervious structure can be hold within 3 mm of the superficial layer where the clogging particles can more easily be cleaned out.For the double-layer pervious structure,smaller top layer thickness led to a better anti-clogging performance.Through the analysis of U1-5,U0.6-5 and U0.3-5,it is found that when the top aggregate particle size of the double-layer pervious structure is between the above two possibilities,the anti-clogging performance is poor.Therefore,the selection of the top layer aggregate particle size should only consider one of the particle transport capacity or the shielding effects,based on the gradation of local clogging particles.By studying clogging of different structures under the same maintenance measures and the cleaning efficiency,it is found that under the same clogging-cleaning environment,the single-layer permeable structure will reach the clogging peak first,and the effective service life will be short.In the double-layer permeable structure,the degree of clogging increases slowly with the increase of the number of clogging-cleaning cycles,the cleaning efficiency is good,it is difficult to cause serious clogging,and the effective life is long.With the decrease of the top aggregate particle size and top layer thickness,the cleaning efficiency increases.According to the three variables of overall porosity,pore diameter and pore shape,9 different models were established for the new tubular permeability structure.The permeability experiment shows that the porosity of tubular permeable structure with the same permeability coefficient can be very small compared with common permeable concrete.Through the anti-clogging ability experiment,it is found that the ability to transport particles has been greatly improved,due to its smooth pore structure,excellent permeability and anti-clogging ability,and the effective service life has been extended.Through the compressive strength experiment,it is found that the compressive strength of tubular permeable concrete structure is significantly better than that of common permeable concrete structure.