Effects of the cross-sectional shape of drain pipes on seepage of rainwater

Road and railway embankments are earth structures that lose stability under rainfall, and accumulation of rainfall causes an elevation of the phreatic surface within an embankment. For these reasons, drainage systems are needed when constructing an earth structure. Drain pipes are one type of drainage system applicable even for an existing earth structure. However, it is difficult to estimate the effects of the drain pipe quantitatively, and design and construction of drain pipes proceed according to past experience. In this study, the authors succeeded in expressing the drainage effects of drain pipes using an existing soil/water/air coupled analysis framework. This study specifically focused on the cross-sectional shape of drain pipes. Five kinds of cross-sectional drain pipe shapes were created, and rainfall infiltration series was simulated using the same procedure for each case. Consequently, the simulations determined that seepage behavior is dependent on the cross-sectional shape of the drain pipe. Furthermore, this analysis found that infiltrated rainwater does not drain when the phreatic surface is located below the drain pipe.