Abstract
Considering the influence of group piles, a prediction model for three-dimensional ground surface settlement induced by circular metro tunnels excavation in incompressible rock masses is proposed based on the stochastic medium theory and the shear displacement method. The surface settlement caused by the metro tunnel opening is divided into two parts. One part is soil mass settlement caused by the metro tunnel opening and calculated by the stochastic medium theory. The other part is the settlement induced by the friction force between the group piles and the soil mass around the metro tunnel cross section and calculated by the shear displacement method. The three-dimensional prediction of the ground surface settlement is obtained by the linear superposition of the two parts. The validation of the proposed prediction approach is proved by comparing with the measured data and the numerical model of the double tunnels under thePuyuanoverpass where metro tunnels undercrossed group piles. The effects of buried depth, radial convergences, center distance of double tunnels, position and size of piles, and group piles are analyzed and discussed. The improved prediction approach can be applied to calculate the three-dimensional ground settlement, especially for the metro tunnels crossing through group piles.
Highlights
The ground surface settlement caused by metro tunnel excavation is an important factor to evaluate the impact of the subway tunnel construction on adjacent structures
According to the shear displacement method [19] and the SM theory (Baochen and Dezhang [15] and Liu [16]), threedimensional (3D) models for predicting ground surface settlement induced by single and double metro tunnels excavations considering the influence of group piles are proposed, respectively
(3) A linear superposition of steps (1) and (2) is adopted, and the ground surface settlement which is caused by the metro tunnel excavation considering the effect of group piles is obtained
Summary
The ground surface settlement caused by metro tunnel excavation is an important factor to evaluate the impact of the subway tunnel construction on adjacent structures. The equivalent ground loss parameters are redefined and the modified analytical formulas of vertical displacement are proposed to predict the tunneling-induced undrained ground movements in a soft ground by Loganathan and Poulos [12]. These approaches make it difficult to predict ground surface settlement accurately because of a number of complex parameters. According to the shear displacement method [19] and the SM theory (Baochen and Dezhang [15] and Liu [16]), threedimensional (3D) models for predicting ground surface settlement induced by single and double metro tunnels excavations considering the influence of group piles are proposed, respectively. The engineering example of metro tunnel which was located at Changsha in China is presented
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