Experimental Study On The Infiltration Characteristic Of Permeable Brick Pavement And Its Influencing Factors

Permeable pavement systems have been widely used in the construction of sponge cities in recent years due to their well infiltration and retention effect on rainwater runoff.However,no mature methods have been developed for monitoring and calculating the infiltration process of permeable pavement in domestic and international research.To address the above problems,this paper focuses on the infiltration characteristic of permeable brick pavement（PBP）and its calculation method,analyses the feasibility of existing infiltration model,and adopts the laboratory physical model,analyses the error of existing monitoring methods,and through the experimental data fitting error analysis,infiltration model with less error was proposed.The research results can provide new ideas and basis for the calculation method of PBP,the main results obtained from this study are as follows.（1）Among the four infiltration models of Horton,Kostiakov,Philip and Green-Ampt,the Horton model has the well fitting accuracy to describe the infiltration characteristics of permeable brick pavement,with its linear regression（R²）greater than 0.96 and the Bias between the fitted and experimental values less than 0.40.And only the parameters i_c and i₀-i_cof the Horton model are related to the maximum infiltration of permeable brick pavement.The values of maximum infiltration rate and stable infiltration rate of permeable brick pavement are close to each other,and the measured values can be used as the parameters of Horton model,and the parameter k is more stable under different monitor sizes and hydraulic gradient conditions.（2）The influence of collection pipes at the bottom of PBP ob Horton model was analyzed in terms of data fitting accuracy and parameter stability.The presence or absence of a collection pipe affects the infiltration process of the permeable pavement and the stagnation effect inside the pavement during the infiltration process.The experiments found that when the monitor size of is small,the accuracy of the Horton model is more likely to be affected by the stagnation effect.Based on the experimental results,it is recommended that the scale of the monitoring area should be greater than or equal to 400mm×400mm when monitoring the infiltration performance of PBP,and the Horton model can be mainly used to calculate the infiltration process of PBP with collection pipes in the substrate.（3）Horton model has a high fitting accuracy under different subgrade gravel gradation,levelling layer media particle size and initial moisture content conditions,where the levelling layer media particle size not only affects the process of infiltration,but also has a greater impact on the fitting accuracy of Horton model,with larger particle size,the fitting accuracy of the model is significantly reduced,under the condition of uniform rainfall intensity,when the levelling layer is coarse sand,the model E_ns is 0.58-0.73,while when the levelling layer is fine sand,the model has a better quality,E_ns is 0.88-0.96.The effect of the gravel grade on the fitting accuracy of Horton model is less,and the initial water content has less influence on the infiltration process of the permeable pavement.In the simulated rainfall conditions,the Horton revised model was proposed and the accuracy of the Horton model was higher under experimental conditions when the revision factor was 4.2(E_ns of 0.87-0.99).（4）The current monitoring methods for permeable pavement are all based on Darcy’s law,of which the permeability coefficients measured by the laboratory normal head method have large errors in relation to the infiltration process of permeable pavement,and the calculated permeability coefficients are different under different hydraulic gradient conditions,which do not meet the conditions of application of Darcy’s law.The three in-situ monitoring methods only have low errors in the calculated infiltration coefficients and steady infiltration rates for specific device sizes and hydraulic gradients,but still have large differences in the maximum infiltration rates for permeable brick pavement.Therefore,when in-situ monitoring is used,suitable device sizes and head heights need to be used,and the in-situ monitoring error is higher for permeable brick pavement with a long dry period.The error in the equivalent permeability coefficient method and permeable brick pavement infiltration process is significantly reduced when the permeable brick pavement substrate has no collection pipes,and experiments have also verified that the equivalent permeability coefficient error is lower for complex media structures such as permeable brick pavement also at large scales.