Equivalent FEM Meshes from Axisymmetric (AXID) to Three (3D) Dimensions Applied to Tunnels in Clay

Efficient tunnel design involves the use of analytical methods and numerical analysis in three dimensions. This paper presents equivalent meshes in axisymmetric conditions (AXID) to three dimensions (3D) using the Finite Element Method (FEM), as well as a displacement nomograph to gauge values of the 3D displacements at a heading and at floor level of a horseshoe tunnel section, and according to a cylindrical symmetry numerical analysis (AXID) from a circular tunnel section. The software used was RS2® for the AXID analysis and RS3® for the 3D simulations. The constitutive model was the Mohr-Coulomb in elastic and anisotropic conditions. Soil parameters: cohesion c, friction angle ϕ, elastic modulus E, Poisson ratio ν and Unit weight γ correspond to endemic soil properties within the city of Morelia. For tunnel simulations circular geometry with R = 5 m of radius and an equivalent area from the circular section to build the horseshoe tunnel section were considered. A total length excavation L = 100 m considering 1 m of the thickness in the 3D mesh in the process of the numerical simulation was done. This study gives the possibility to obtain the maximum 3D displacement for a horseshoe tunnel, carrying out an axisymmetric analysis in RS2® or using the proposed displacement nomograph.