Safety assessment for a ballast railway induced by underground subway tunnel blasting: A case study

Modern railroad infrastructure is subject to blast vibrations. The dynamic safety of an operating railroad under the influence of tunnel blasting is a primary problem for metro development in urban areas. In this paper, the blasting excavation of Wuhan Metro Line 5 was selected as a case. The ballast rail- sleeper- ballast bed composite structure numerical model was developed and validated in order to evaluate the ballast railway’s safety. The smoothed particle hydrodynamics element was chosen to replicate the ballast bed due to the instability and unpredictability of the ballast bed constructed from crushed stone. Further analysis was conducted on the dynamic response characteristics of the ballast rail-sleeper-ballast bed composite structure. On the basis of the parameter calculation and analysis, a prediction model of the blast vibration velocity of the ballast rail under blasting conditions was developed. Next, the rail was simulated as a semi-infinite Euler beam and placed on the Kelvin foundation to calculate the rail displacement at the train’s limited operation speed. By substituting the maximum rail displacement when the train is running at maximum speed into the rail velocity prediction model, it is possible to determine the maximum blast velocity that the rail can withstand in this instance. In this case, the ballast bed, sleeper, and ballast rail were also deemed safe.