4Federal Highway Administration.Guidelines for the Design of Subsurface Drainage Systems for Highway Structural Sections[R].Prepared by the Joint Venture of H.R.Cedergren,Sacramento,and Ken O'Brien & Associates,Long Beach and Ventura,California,1972;issued 1973
5AASHTO.AASHTO Guide for Design of Pavement Structures[S].Washington D.C.,2002
