Optimizing arching creation for Abou Muharik Tunnel in Egypt using numerical analysis: Fid-Bau Portal

Optimizing arching creation for Abou Muharik Tunnel in Egypt using numerical analysis

Akl, S. A. / Metwally, K. G.

Abstract This paper investigates the arching action occurring in sand dunes and protection embankment of the “on ground” Abou Muharik Tunnel. The precast concrete tunnel is proposed to protect the planned railway line passing from phosphate rich Abou Tartour Area, and through a zone of complex chain of sand dunes in Abou Muharik. Two alternatives are proposed by the designers for the embankment of the tunnel: 1) Using compacted sand for the entire backfill around the tunnel and 2) Embedding a layer of Pneusol within the backfill above the tunnel. The paper presents numerical simulations of both designs using the Finite Elements Program ANSYS. The simulation results give insights on the arching mechanism occurring within the sand dunes and protection layers. Analysis shows that using a Pneusol layer within the protection embankment relieves around 14% of the reaction forces at the tunnel foundation. Eventually, the Marston effect on the tunnel foundation is almost eliminated. The paper also presents a parametric study to optimize the specifications of the Pneusol layer. The study shows that a 10 m wide layer with stiffness that is 20% of that of embankment soil produces most favorable straining actions in the tunnel.