Numerical determination for optimal location of sub-track asphalt layer in high-speed rails

Well-graded asphalt mix with the merits of high sound absorption, low water permeability, excellent strength, and easy construction is an important option for high-speed railway substructures. On the basis of finite element method, a model with conventional ballasted trackbed (T0) and four ballasted trackbeds models with different positions of asphalt layer were analyzed, in which 15 cm thick asphalt layer was used to replace the different sub-track layers, the bottom and the top of upper subgrade and of ballasted trackbed, named as T1, T2, T3, and T4, respectively. The results showed that the range of peak vertical accelerations on the top of subgrade surface of T2 and T4 were smaller than T1 and T3; T1 and T2 perform better in decreasing the maximum vertical deformation of subgrade than T3 and T4; the maximum transversal tensile strain of T4 is almost twice than the other three. The trackbed bears more stress when the asphalt layer is located at the lower part of railway trackbed.