Benchmark of calibrated 2D and 3D track models for simulation of differential settlement in a transition zone using field measurement data

Two models for time-domain simulation of vertical dynamic vehicle–track interaction and prediction of differential settlement in a transition zone between a ballasted track and a Moulded Modular Multi-Blocks (3MB) slab track are calibrated and verified using field measurements from a test site on the Swedish iron ore line. The dynamic analysis is performed using two-dimensional (2D) and three-dimensional (3D) track models in MATLAB and ANSYS, respectively. A seven-parameter representation of the ballast and subgrade is applied in the 2D model. It considers sleeper coupling through the ground via a discretised mass-spring-damper system. The more extensive 3D model includes a solid finite element (FE) model of the layered soil foundation with properties determined from a multichannel analysis of surface waves (MASW) carried out at the test site, and with perfectly matching layers (PML) added at the boundaries. The measured responses include rail receptance functions from both track forms on either side of the transition, as well as transient responses in terms of sleeper displacements and rail bending moments generated by the passing heavy-haul traffic. Both models are employed to simulate the passage of an iron ore freight vehicle through the transition zone. The accumulated settlement for one year of traffic is predicted using an iterative approach and compared with the measured long-term sleeper settlement. Good agreement is observed between the measurements and the settlements forecasted by both models, with the simulation time being approximately 25 times shorter for the 2D model.