Abstract: In order to determine a better solution for composite lining design of heavyhaul railway tunnels, the composite lining structure design of a singletrack heavyhaul tunnel on the Menghua railway is optimized and analyzed by using a field test and a numerical simulation method. The concrete and the grid steel frame are monitored and measured using embedded strain and stress gauges in the lining structure of the test section. The tunnel excavation support process is simulated using finite element software. In addition, the deformation and the internal force of the primary support structure under different working conditions are analyzed to evaluate the structural safety. The results show that: when the singletrack tunnel in Grade Ⅳ surrounding rock is constructed, (1) using the bench method, the crown moves upward before the primary support is closed; (2)the internal force of the primary support is mainly the axial force (pressure); (3) the corresponding bending moment shared by the shotcrete and the steel frame is relatively small, accounting for approximately 70% to 90%; and (4) the densification of the steel grid truss reduces the shotcrete load proportion and improves its safety.

Key words: heavy-haul railway tunnel, composite lining, numerical simulation, monitoring measurement, bench method, lining optimization