Study On Freeze-thaw Damage Experiment Of Permeable Pavement And Anti-freezing Measures

In recent years,with the rapid development of urbanization and the sharp increase of hardened area,the problems of urban runoff pollution,ecological damage and less groundwater recharge are becoming more and more prominent.The traditional fast drainage mode not only destroys the original hydrological cycle,but also causes serious water pollution problems due to the direct discharge of runoff pollution load into nearby river channels.Furthermore,the urban drainage system,especially the old urban pipe network,does not match the increasing displacement,resulting in serious waterlogging and combined overflow pollution(CSO)problems.As an important Rain Water source emission reduction facility,permeable pavement(permeable pavement systems)has the function of reducing urban rainwater runoff,replenishing groundwater level and reducing runoff pollution load.But in the cold area,affected by freeze-thaw conditions,the vulnerability degree increases significantly,which has been widely concerned by researchers.This study takes the permeable pavement as the main research object,first through the investigation way,summarizes the permeable pavement frost heave damage phenomenon,from its material,the emptying time,the winter snowfall quantity,the freeze-thaw cycle times,the freezing rate and so on angle,has revealed the influence permeable pavement frost heave damage degree main factor.Then through the freeze-thaw cycle experiment,the main factors affecting the frost resistance of permeable pavement and the frost resistance of different materials in leveling layer and base course are studied.Through the above two experimental data,the prevention measures of frost heave damage of permeable pavement are put forward.The conclusions are as follows:(1)The frost heaving damage of permeable pavement is caused by the frost heaving force around the pore caused by the volume expansion of water icing in the storage volume.Taking the paving of permeable brick as an example,it is revealed that the maximum frost heaving stress of ceramic permeable brick with compressive strength of 30 MPa is 1.67 MPa.when the maximum frost heaving stress of cement permeable brick is 1.42(2)The influencing factors of frost heaving damage of permeable pavement include water saturation,porosity,number of freeze-thaw cycles,and discharge time of snow melt runoff.Among them,the water saturation of permeable pavement is the decisive factor to produce frost heaving damage,and its critical water saturation value is 90%.When its water saturation exceeds this value,the frost heaving damage degree is larger,and the frost heaving damage degree is very small when it is lower than this value.(3)In order to improve the service life of permeable pavement,design methods such as adding water guide pipe or seepage discharge plate,filling joint with dry sand or setting expansion joint,adding auxiliary facilities such as planting grass trench or biological retention zone are proposed.