Numerous high rise buildings are supported by deep foundations in major cities or urban areas.rnDue to the rapid increasing demand for infrastructures construction in congested urban areas,rntunnels are often preferred for under ground transportation. The construction of tunnels are closernto some existing piles foundations will affect pile capacity and stability due to soil deformationrncaused by vertical and horizontal movement, which changes the axial load distribution along thernpiles.rnIn this study, the effect of a 6m open face advancing tunnel on a three by three group pile in c- Ï•rnsoil has been investigated using three dimensional finite element analysis software (PLAXISrn3D). Hardening soil (HS) constitutive model and isotropic elastic model for piles, pile cap,rntunnel lining, and tunnel boring machine (TBM) were used for analysis. A parametric study hasrnbeen carried out to investigate the behavior of piles through varying ratios of tunnel depth (H) torntunnel diameter (D) (namely H/D= 2.0, 2.5, and 3.0).rnFrom the analysis result, the factor of safety of the pile was reduced from 3.0 to1.62 due torntunnel advancement 2m near to the pile tip, large pile settlement was observed when the tunnelrnface below the pile tip(H/D=3.0). And also the load carrying capacity of the pile at the basernsignificantly decreases. In addition, skin friction of the pile was significantly decreased when therntunnel approaches to the shaft of the pile.