Abstract: The ventilation shaft for a river crossing tunnel had a large embedment depth and closed to the river water and levee system with complicated geological and hydrological conditions. Higher safety measures were required due to the penetration of the saturated sandy layers. A rectangular box frame structure with slab and beam system was utilized for the ventilation shaft. Due to the numerous required openings on the shaft body, the structure has a typical threedimensional structure type and could only be simulated by the threedimensional analysis. A numerical model was established for the ventilation shaft. Analyses were performed and it was concluded that the middle portion of the shaft had larger stress and the structure design was appropriately performed.

Key words: Saturated Sand Layers, Ventilation Shaft, Three-Dimensional Modelling, Refinement, Three-Dimensional Stress State