Buoyancy effect on shallow tunnels. (February 2019)

• Record Type: Journal Article
• Authors: Vitali, Osvaldo P.M.; Celestino, Tarcisio B.; Bobet, Antonio
• Is Part Of: International journal of rock mechanics and mining sciences. Volume 114(2019)
• Page Start: 1
• Page End: 6
• Publication Date: 2019-02
• Subjects: Shallow tunnel -- Numerical modeling -- Finite element method -- Buoyancy; Rock mechanics -- Periodicals; Soil mechanics -- Periodicals; Mining engineering -- Periodicals; Roches, Mécanique des -- Périodiques; Sols, Mécanique des -- Périodiques; Technique minière -- Périodiques; 624.151305
• DOI: 10.1016/j.ijrmms.2018.12.012
• Languages: English
• ISSNs: 1365-1609

Abstract

Abstract: When a shallow tunnel is excavated, an overall upward movement appears as a result of the weight removal from the excavation. This movement is analogous to buoyancy. When numerical simulation of shallow tunnels is used, the magnitude of the upward movement increases with the depth of the lower boundary, defined as the distance from the tunnel center to the bottom of the mesh. This seems counterintuitive, and yet it is mathematically correct. This paper investigates the influence of the assumptions made to model the buoyancy phenomenon numerically, and specifically the (typical) plane strain and elasticity assumptions. Three-dimensional and two-dimensional plane strain numerical models are carried out using a linear elastic model, where the influence of the ground stiffness increasing with depth is assessed. The results show that the buoyancy effect, i.e. increasing upwards movements with depth of the lower boundary, decreases when the ground stiffness increases with depth.