Abstract:

The problem of tunnel lining uplifting and ground surface heave during the excavation of large diameter shield tunnel under shallow overburden has been theoretically investigated with the project of Shanghai South Hongmei Road rivercrossing tunnel. The buoyancy which causes the tunnel lining uplifting is classified into the timedependent static buoyancy of slurry and the dynamic buoyancy generated by grouting. Equivalent formation spring stiffness coefficients are defined for the section where the buoyancy is available and the section where the slurry has hardened, respectively, after which the model of tunnel lining uplifting is established according to the theory of Winkler foundation beam. The resulting lining displacement is used to calculate the squeezing width of the soil above the excavation surface, which is further converted into "reverse loss" of soil formation. And then the uplift curves for ground surface in transverse and longitudinal directions are derived. The results indicate that: (1) The predicted ground surface heave in transverse direction is characterized by normal distribution and matches well with the data measurement. (2) The model accurately predicts the maximum ground surface heave in longitudinal direction and matches well with the data measurement until the heave drops. (3) Furthermore, ground surface heave exists only within a certain period after the shield passes and its value firstly increases and then decreases to zero.

Key words: shield tunnel, tunnel lining uplifting, ground surface heave, monitoring data