Cavity influence on fatigue performance of heavy haul railway Tunnel’s bottom structure

Abstract

The smoothness of tunnel base directly affects the safety of train operation, and tunnel base diseases are usually difficult to detect and deal with due to the distinguishing features of heavy haul railway, the base diseases become one of the most harmful tunnel diseases. Therefore, with the increasing axle load and the basal deterioration of the existing heavy haul railway in China, studying the fatigue performance of the tunnel bottom structure is essential. A 3D train-tunnel-surrounding rock numerical model is established to obtain the dynamic response of the tunnel bottom structure under 30 t axle load trains. Then refer to the stress state and fatigue vulnerable position which are originated from the numerical simulation, a series bending fatigue tests are carried out to study the cavity influence on fatigue performance of heavy haul railway tunnel’s bottom structure in this paper. A non-linear cumulative damage model is proposed to quantify fatigue damage evolution characteristics of tunnel bottom structure with base cavity through the tests. The results suggest that, the base rock cavity remarkably reduces the fatigue life of the specimen and increases the development rate of damage; the existence of cavity not only deteriorates the bearing capacity of the structure, but also greatly improves the dynamic response and stress level of the bottom structure and base rock, which has multiple adverse effects on the fatigue performance of the tunnel bottom structure, and also accelerates the expansion of the cavity itself.