Parametric Study on the Influence of Tunneling on Adjacent Deep Foundation

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Addis Ababa University


Numerous high rise buildings are supported by deep foundations in major cities or urban areas. Due to the rapid increasing demand for infrastructures construction in congested urban areas, tunnels are often preferred for under ground transportation. The construction of tunnels are close to some existing piles foundations will affect pile capacity and stability due to soil deformation caused by vertical and horizontal movement, which changes the axial load distribution along the piles. In this study, the effect of a 6m open face advancing tunnel on a three by three group pile in c- ϕ soil has been investigated using three dimensional finite element analysis software (PLAXIS 3D). Hardening soil (HS) constitutive model and isotropic elastic model for piles, pile cap, tunnel lining, and tunnel boring machine (TBM) were used for analysis. A parametric study has been carried out to investigate the behavior of piles through varying ratios of tunnel depth (H) to tunnel diameter (D) (namely H/D= 2.0, 2.5, and 3.0). From the analysis result, the factor of safety of the pile was reduced from 3.0 to1.62 due to tunnel advancement 2m near to the pile tip, large pile settlement was observed when the tunnel face below the pile tip(H/D=3.0). And also the load carrying capacity of the pile at the base significantly decreases. In addition, skin friction of the pile was significantly decreased when the tunnel approaches to the shaft of the pile.



Tunneling, Parametric Study, Adjacent Deep Foundation