PET aggregates were produced by mixing heated PET flakes with frictional soils. Using these artificially-made PET aggregates, horizontal drain tests in the laboratory, pilot scale model tests were conducted for the evaluation of the drainage characteristics of PET aggregates. Laboratory horizontal drain tests were conducted under twenty different conditions varying mixing ratios and surcharged pressures. Moreover, by utilizing the aggregates with a mixing ratio producing the lowest variation in terms of permeability against applied load, large scale tests were performed. Reliability of the test results was evaluated from comparison with the results of the laboratory horizontal drain test.