Analysis of instantaneous surface settlement during tunnel construction in composite stratum

Abstract

It is important for shield tunnelling safety to predict and control the instantaneous surface settlement. Particularly, the complex geological condition can make accurate prediction more difficult. To adapt to the stratum distribution, a semi-analytical method is established by introducing the finite layer method into tunnel mechanical analysis. Firstly, based on the elastic solution of the finite layer method, the horizontal flexibility coefficient of tunnelling and the surface settlement are obtained by applying effective thrust to the excavation face. Secondly, two influencing factors are analyzed, including the penetration of shield tunnelling and the Poisson ratio of geotechnical parameter. The relationship formula between the measured value and the theoretical value of the maximum settlement is derived through data fitting. Finally, the settlement prediction method of tunnelling is proved to be practical, which provide a new ideal for the mechanical analysis of tunnels in composite strata.