Effects of suffosion-induced contact variation on dynamic responses of saturated roadbed considering hydro-mechanical coupling under high-speed train loading

Recent experience of high-speed railway in operation has indicated that the hydro-mechanical coupling effect under dynamic loads from high-speed train may lead to excessive pumping of fine particles in saturated roadbed surface layer. This can result in large variations of contact condition between track and subgrade structure layers while study on this issue remains scare. Based on the theory of fluid dynamics in porous medium and the vehicle-track-subgrade coupling vibration theory, a numerical model is established to evaluate the dynamic responses of saturated roadbed surface resulting from the contact condition variation under the high-speed train load considering the hydro-mechanical coupling effects. A concept of three contact types (fully continuous contact, vibration contact and contact loss) is proposed and three contact shape forms (rectangular, cosine and elliptical shapes) simplified for describing contact damaged zones are compared in terms of dynamic responses (stress, pore water pressure, seepage velocity) evaluated. Also, time-frequency analysis is performed to investigate the influence of contact variation on dynamic responses of roadbed surface in aforementioned contact types. Results show that this progressive development of contact damage can pose extra great stress and pore-water pressures in roadbed and a critical length of contact loss zone is suggested.