Field assessment of a subgrade-culvert transition zone constructed with foamed concrete in the ballasted railway

The subgrade-frame culvert transition section of a railway has been designed as an inverse trapezoidal shaped and filled with foamed concrete. Monitoring tests have been carried out to explore the performance of this structure, including long-term base settlement and base stress monitoring and dynamic response parameters monitoring. Based on the testing data, the distribution laws of the base stress and base settlement along the longitude direction of the transition section subgrade have been obtained. Distributions of the acceleration, dynamic displacement, and dynamic stress along the subgrade depth and along the longitude direction of the subgrade have been analysed respectively, and the attenuation coefficients of these three kinds of dynamic response parameters have been calculated. Also the relationship between the thickness of the foamed concrete layer and the dynamic response parameters has been explored. These demonstrated that the foamed concrete can improve the dynamic performance of the structure.