Three dimensional finite element analysis for preliminary establishment of tunnel influence zone subject to pile loading

Urban development often involves the construction of infrastructures that require deep foundations or piles. Due to the existence of tunnels, the need to construct deep foundations in close proximity contributes to possible damage to the tunnels and operational safety concern. The concept of influence zones has been proposed as restrictive guidelines for construction adjacent to underground tunnels. However, the current influence zones are based on the conventional assumption of soil failure due to tunnelling rather than on an understanding of the pile-tunnel interaction. This paper thus analyses the impacts of piles under loading on the subway tunnel of the Mass Rapid Transit Authority of Thailand in Bangkok using the 3D finite element method. The analyses are carried out to investigate factors in tunnel deformations. The results show that the significant factors are the relative position of the pile tip with respect to the tunnel position as well as the soil type where the tunnel is located. In addition, this paper tentatively proposes a new influence zone for pile construction adjacent to the existing tunnel.