Observational control of slurry shield tunnels with super close spacing under the nearby bridge abutments loads

Abstract

The Rinkai Line is a new railway line of around 12.3 km in length, connecting Shin-Kiba Station with Osaki Station through the new Tokyo subcentre on the waterfront in Tokyo. On March 1996, a section of about 4.9 km between Shin-Kiba Station and Tokyo Teleport Station was put into service as a first phase. As part of a second-phase construction, the Rinkai Line Higashi-Shinagawa Tunnels have been constructed by slurry shield tunnelling method. This tunnel project stretches about 983 m from Tennozu Isle Station to Shinagawa Seaside Station. This project required that the parallel twin tunnels had very close clearance (the minimum clearance 1/4 0.6 m). Furthermore, tunnel excavation was located very close to some important existing sensitive structures, such as abutments of bridge and an oil tank. At the Higashi-Shinagawa bridge section, the shield drove through just underneath the piled foundations with the minimum clearance of around 3.0 m. Mair and Taylor (1997) reported some case histories related to the response of buildings on piled foundations to ground movements induced by tunnel process. However, very limited published case histories related to the evaluation on the effect of tunnelling on piled foundations exist so far because of including the complex interaction mechanisms. Therefore, careful management of the tunnelling works was required. In order to prevent excessive settlements and to ensure the safety of the adjacent existing structures, detailed in situ monitoring of the nearby structures, surface and subsurface ground movements was planned and implemented. An automatic measuring system was adopted as a measure of controlling ground movements, and the optimum control value was established for soil pressure inside the shield chamber for stabilizing tunnel face. Furthermore, the monitoring of segmental lining was also carried out to confirm the safety of the segmental lining design at very closely excavated sections. At the Higashi-Shinagawa bridge section, grout injection from the preceding shield was planned and carried out to stabilizing the surrounding ground as an auxiliary measure. It worked quite well to suppress the loosening of the surrounding grounds and the movement of the piled foundations. This paper describes the in situ monitoring results of the existing bridge pier movement during the shield construction. Main conclusions are as follows: (1) By careful and well-controlled tunnel excavation, detailed monitoring of the ground movements and rapid data processing, it has achieved well-controlled volume losses to values less than 0.5% in spite of the tough tunnel construction with super close spacing and the existing nearby structures. (2) Bridge pier's settlements were well controlled, being less than 4.0 mm, and the shield construction has successfully completed without any problems. (3) The grout injection from the inside of the preceding tunnel could effectively control the loosening of the surrounding grounds and the pile settlements. (A) Reprinted with permission from Elsevier. For the covering abstract see ITRD E124500.