Physical Model Tests and Discrete-Element Simulation of Pile and Soil Displacement Response Induced by DOT Shield Tunneling Based on Transparent Soil Technology

Abstract With the advantages of saving underground space, small construction impact, and saving cost, the double-O-tube (DOT) shield tunneling construction technology has been used many times in the tunnel construction of particular areas with dense buildings. This paper describes a device developed for modeling DOT shield tunneling based on transparent soil technology and investigating the displacement response of pile and soil during the construction process of a DOT shield tunnel adjacent to an existing pile, which is considered in the uniform convergence mode (UCM) of soil loss. Meanwhile, the displacement response of pile and soil in the nonuniform convergence mode (NCM) was analyzed contrastively using the discrete-element method (DEM). The results showed that the displacements of soils around the pile are limited and the shapes of the soil settlement curves above the DOT shield tunnel change approximatively from “V” to “W” with the depth of the soil layer increasing. When the buried depth of the pile was 1.0D, the settlements of the pile and soils were obviously affected by the convergence mode. The maximum surface settlements were 1.52, 1.34, and 1.21 times larger under NCM than those under UCM, while the maximum horizontal displacements of the vertical soil layer beside the pile were 1.92, 1.83, and 1.80 times larger under NCM than those under UCM, respectively, corresponding to H/D = 1.0, 1.5, and 2.0. With the buried depth of the DOT tunnel increasing, the deflection and settlement increased first and then decreased. When H/D = 2.0, the excavation of the DOT tunnel could barely cause pile deflection under NCM.