Abstract: As a novel filter layer material, foam plastic has good application prospects in the sponge city infiltration system. Yet, the selection of filter layer specifications in the presence of different storm-water suspended solid characteristics and the maintenance of filter layer after clogging are still problems to be solved. In view of this, we acquired the particle size gradations and concentration ranges of storm-water suspended solids in the study area through sampling and analysis at a typical site, and then simulated the physical clogging process of foam plastic filter layer via indoor tests. We divided the storm-water particles into five groups according to their gradations and prepared suspension solutions respectively for the filter layer infiltration simulation test. We suggest that for fine particles of [0.1,0.25) mm and <0.1 mm, the pore size of the corresponding filter layer with the best retention effect is 80 ppi and 100 ppi, respectively. Moreover, we prepared solutions of various concentration with suspended solid particles of combined gradations to carry out infiltration simulation experiments for two types of filter layers, and obtained the change rules of the dropping rate of foam plastic filter layer's permeability coefficient with the suspension concentration as follows: in the presence of the same filter pore size, greater concentration of rainwater suspended solid led to larger clogging rate; at the same suspension concentration, smaller pore size of filter gave rise to faster clogging. The changes in permeability coefficient were also proven by turbidity analysis results of the filtrate.

Key words: foam plastic, clogging, suspension particle size, layer pore size, filtrate turbidity