Unsaturated Seepage Analysis Of Pavement Structure In The Rainfall And Drainage Performance Assessment

According to a lot of investigations on highway pavement service condition, inadequate subsurface drainage of pavement has been identified as a primary cause of unsatisfactory pavement performance and premature failures. Basing on the research informations at home and abraod, combining the pavement types and pavement drainage design on the test section of ChangDe-Jishou highway, some analyses are done on the unsaturated seepage in pavement subsurface under rainfall condition, by the means of the theoretical analysis, in-suit testing and numerical simulation. The research work of the paper involves several aspects as follows:(1) The actural criceria of to evaluate the effectiveness of the pavement subsurface drainage system and the design method of the pavement subsurface drainage system are introduced. The internal condition, request and form aboat intercalate the pavement subsurface drainage system are introduced.(2) The basic characteristic of unsaturated porous media and the govering equation of unsaturated seepage are introduced. The boundary conditions of unsaturated seepage under rainfall condition are attained.(3) Based on unsaturated seepage theory, a finite element software named SEEP/W is used to numerical simulated unsaturated pavement seepage under rainfall condition, and analysis the orderliness of infiltration in any unsaturated road structures. Volumertric water content curves are plotted and the time of draw 50% water(t₅₀) are accounted to analyze subsurface drainage performace with drainage base layer or not, different permeability of drainage base layer, different water tables, different surface layer materials and have cracks on pavement surface or not.(4) Site tested on infiltration of medium divider under rainfall circumstance. Based on unsaturated soil seepage theory, a finite element software named SEEP/W is used to numerical simulated unsaturated medium divider infiltration, then analyzed drainage performance and the orderliness of rainwater infiltration in medium divider soil comparing with site test. The infiltration of highway medium divider is studied using finite element software SEEP/W based on unsaturated soil seepage theory. Variant situations with different rainfall flux, rainfall duration, and soil types are analyzed and compared.