Earth Pressure on Linings of Shield Tunnel

Abstract

Total weight of overburden is usually considered in calculation of vertical earth pressures on shield tunnel lining segments unless the arching effect of soil above tunnel can be justified. Theoretical approach has been used to estimate the vertical earth pressures on tunnels with soil arching effect. Previous studies on field monitoring data indicate that measured vertical earth pressures on tunnel linings account for only 40 to 50 percents of the total overburden, except for cases in very soft clay formation. Moreover, the measured vertical earth pressures are usually lower than the theoretical estimates. In this paper, a numerical study using a software package (FLAC) is conducted on the earth pressure distribution on shield tunnels considering the tunnel construction and various overburden thicknesses. The results indicate the vertical earth pressures on linings of shield tunnels at depths of 20m, 25m, and 30m in T2 zone of Taipei area are respectively 45%, 46%, and 42% of corresponding total overburden pressures. Furthermore, the estimated lateral earth pressure coefficient is close to K a .