An Equation to predict ground surface settlement due to metro tunneling using EPB TBM

Shallow excavation such as tunnels may cause ground movement and this movement can induce ground surface settlement. Tunnels may be constructed in urban areas with high population density and therefore damages on buildings and structures due to settlement are possible. Thus it’s vital to predict ground surface settlement due to tunneling. There are several factors which affect the magnitude of ground surface settlement due to tunneling by means of EPB TBMs such as depth، face pressure and grouting pressure. In the first section of this paper all the effective parameters on ground surface settlement due to tunneling in clay by means of EPB TBM are introduced. Then using numerical modeling with Plaxis 3D TUNNEL and using Shiraz metro tunnels data، and with parametric analysis، effect type and magnitude of these parameters on settlement are investigated. Using sensitivity analysis، the most effective parameters on settlement are presented. Carried study showed that face pressure، grouting pressure، contraction، soil elastic modulus and depth have the most effect on settlement. In the second part of this paper using numerical modelling، the process of tunnel construction in saturated clay by means of EPB TBMs is modeled. Then the magnitude of ground surface settlement due to tunneling in 27 models is used to develop a statistical equation using multiple regression analysis. Finally the equation is compared to Shiraz metro tunnels instrumental data. This comparison confirms the equation. Using this equation is very simple and all of required parameters exist in all metro projects. Furthermore، the equation’s error is acceptable.