Interaction between two-arch tunnel and pile supported bridge – An experimental investigation

This paper presents the results of a laboratory investigation on the interaction between a two-arch tunnel and an existing pile-supported bridge. A series of reduced-scale model tests were conducted using a model reduced from a prototype tunnelling condition with due consideration of the similitude law. A number of variables were considered, including the clearance between the pile tip and tunnel, offset distance of bridge pier from tunnel center and bridge load. The results indicated that the presence of the piled bridge increases the tunnel crown settlement and primary lining strains, and column load. It was also shown that the response of the piled bridge to the two-arch tunnel construction may be significantly affected not only by the clearance between the pile tip and tunnel, but by the lateral location of the piers with respect to the tunnel. In addition, the precedent (left) tunnel excavation induced greater ground movements, thus pier settlements, than the following (right) side tunnel excavation. The effect of the following (right) tunnel excavation on the precedent (left) tunnel was greater when the interaction level between the two-arch tunnel and piled bridge was higher. Practical implications of the finding are discussed in detail.