ABSTRACT
The first subway project is under construction to serve the mass transit system of Bangkok city. The system consists of dual tunnels about 20km long with 18 subway stations. The tunnells are seated in the firm first stiff silty clay layer between 15–22 m. depth below ground surface having outside and inside diameter of 6.3 m., and 5.7 m., respectively. The empirical approaches for predicting surface settlement after completion of tunnelling based on Peck (1956) and O’Reilly & New (1982) were presented. The newly developed correlation for predicting subsurface settlement was also proposed. The back analysis based on plain strain FEM analysis was also presented and agrees with field performance. The shear strain of FEM analysis is in the range of 0.1–1% and agrees with the results of self boring pressuremeter tests.
