Development of low-strength stabilization method for fouled ballasted tracks

In ballasted tracks on railways, fine fraction content (hereinafter referred to as “Fc”) mixed in ballast increases due to repeated train loads or track repair work using ballast tampers. When the Fc increases and becomes “fouled ballast”, settlement of ballasted track tends to increase even after track repair, which results in a rise in maintenance frequency. In such cases, ballast replacement is the standard measure applied to reduce frequency of maintenance. However, ballast replacement is costly, and railway operators therefore need countermeasures to prevent large settlement which are both low cost and quick enough to implement during periods of track work carried out at night. This study describes the development of a new repair method which reduces sleeper settlement by mixing super-quick hardening cement and polymeric stabilizer (hereinafter referred to as “stabilizing materials”) with fouled ballast. This method uses a ballast tamper and weakly stabilizes fouled ballast to allow tamping even after stabilization, hereinafter referred to as the “low-strength stabilization method”. This study investigates the relationship between sleeper settlement and amount of stabilizing materials needed for this low-strength stabilization method, and examines the settlement reduction mechanism through cyclic loading triaxial compression tests. Confirmation of settlement reduction was conducted through full-scale cyclic loading tests.