Maintaining the serviceability and safety of the railway transportation system is an essential national engineering project. Today, most railway systems still use ballast as the primary foundation. Frequent mud pumping occurs on the ballast foundation, which makes the railway system's safety and reliability questionable. It is immediately essential to explore the mechanism of mud pumping. If the key factors causing mud pumping can be clarified, it will significantly help reduce railway maintenance costs and improve reliability and safety in the future. Conducting a full-scale ballast foundation cyclic load test to simulate the mud pumping behavior and explore its development mechanism is critical research. To this end, this article will demonstrate using the train load measured on-site and numerical simulation methods to calibrate the model size for subsequent physical testing.