Influence of construction and operation of pile foundation of overpass on existing tunnels

The overpass to be built adopts capped pile groups to support the overpass piers. There are totally eight over-crosses close to the existing shallow-buried tunnel of Metro Line 2 in Tianjin with the minimum distance of 6.5 m between the tunnel and the piles. Since the pile foundation on the tunnel are constructed under the poor subsoil conditions, the impact of the construction of piles and the considerably large vertical load to be carried by the piles must be evaluated considering the small distance between the pile foundation and the tunnel. A three-dimensional finite element method is established to simulate the construction process of pile foundation and the load carried by the piles to investigate the effects on the underground tunnel. The influences of single- and multi-overpass piers supported by pile groups on the adjacent existing tunnel and track are summarized. The corresponding deformation-controlled countermeasures are proposed.