The impact of large-scale tunnel excavation on neighboring structures in dense urban areas: The characteristics of interaction

The traffic congestion in many cities in China especially during the peak hours has led to the building of new subways. The development of public transportation can reduce the use of private vehicles, thereby reducing road traffic congestion. In this paper, a case study in Chongqing City including a big tunnel section with a diameter of 26 m will be shown. In addition, two small tunnel sections laying orthogonal with the main tunnel (big section) will also be studied. Wind ventilation is located between the two small tunnels have also been excavated. To investigate the deformation characteristics of such dense excavation procedures 3D FEM model has been built. The numerical simulation resulting data with the site monitored determined points has been compared. However, the comparison shows good agreement. Moreover, according to some sections of the big tunnel which includes a dense urban area with the above structures, a raft building with different piles diameter as a foundation support has been considered. Based on the numerical simulation as an effective tool, huge data has been generated to investigate the extension of the spreading of the influenced zone due to the excavation of three types of tunnels: the first is the big tunnel section with a diameter of 26 m. The second is a tunnel section with 13 m. While, the final tunnel case is twin tunnels, each tunnel has a diameter of 13 m. These tunnel cases have been studied and the interaction between (different piles diameter + raft) systems and different tunnel diameters has also been investigated. The influenced area has been proposed according to each tunnel case. However, the results show that 'R' ratio which represents the pile settlement after the excavation divided by the pile settlement before the excavation has much more difference in comparison with the extension area of the disturbanc