go back button
September 05, 2019

Buoyancy effect on shallow tunnels

Osvaldo P.M. Vitalia, Tarcisio B. Celestinob, Antonio Bobeta




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."


Read Now!




Search Keyword search-icon

      Popular Tags

      Research Paper Tunnel Foundation Excavation Underground Dam Construction stage analysis Soil Structure Interaction 2D Consolidation Pile Wall geotechnical Seepage Structural Analysis Tutorial 3D modelling Ground Rail Seismic Slope groundwater midas Gen pressure settlements Alpine Base Tunnels Analysis of Finite Element Methode Combined Pile-Raft Foundations Complex Concrete Conference Couple Analysis Coupled Analysis DDM DFI Design analysis Displacement Diversion Tunnel Double shield TBMs Dynamic El Nino Elastic modulus Embankment Excavating Finite Element Foundation Differential Settlements Fracod Geometry High-rise building Highly Expansive Hoek-Brown criterion Intersection Live Load Analysis Long Drought Season Long deep tunnels Mcgill Monte Carlo ONKALO Parametric study Progressive Failure Purdue Raft Foundations Safety Factor Shrinkage Simultaneous Blasting Soil Soil Modeling Spalling Spalling prediction Squeezing Structural Design Substructure Thermal Analysis Vertical stress Void Creation alluvial anisotropic properties axial shear stresses barrette raft base buoyancy phenomenon numerically collapse compact crystalline rock deepening elasticity finite element method foundation design fractured zone geological investigation geomechanical parameter geophysics ground resistance hydraulic behavior instrumentation junction limestone cavity linear-elastic ground load transfer curves load transfer mechanism mechanism non linear analysis numerical analysis of pile group numerical method o-cell loading packer permeability testing pile loading portal pressuremeter testing rail tunnel retaining wall seismic loading sensitivity analysis shaft shallow depths spillways standard penetration testing stress and strain subsea temporary supports