Abstract
The construction of a deep and large foundation will inevitably impose stress and deformation on the existing shield tunnel structure. Based on the two-stage analysis and the Pasternak foundation beam model, the analytical solution for the existing tunnel deformation is derived by taking the grouting pressure and water buoyancy into account in the total tunnel deformation. Using FLAC 3D software, based on the soil-structure interaction model, the variation law of the tunnel uplift value under partition excavation of the foundation pit is studied and the variation law of the stress field and displacement field of the tunnel under the MJS method is analyzed and compared. The results of this paper are worthy of reference for similar projects.
Highlights
With the rapid construction of urban underground space development, it is often encountered that the new foundation pit or tunnel project is adjacent to the existing tunnel construction
The unloading of foundation pit excavation will cause the change of the displacement field and stress field of the underlying shield tunnel
Many scholars have used theoretical calculation [6,7,8], numerical simulation [9,10,11,12], and measured analysis [13, 14] to conduct in-depth analysis on the deformation of the underlying tunnel caused by foundation pit excavation under different geological conditions or construction schemes
Summary
With the rapid construction of urban underground space development, it is often encountered that the new foundation pit or tunnel project is adjacent to the existing tunnel construction. Zhang et al [17] considered the dewatering effect of the foundation pit and obtained the theoretical calculation formula of additional stress and vertical deformation of the underlying existing tunnel caused by upper excavation and dewatering. When calculating the vertical deformation at any position of the tunnel caused by the excavation of the foundation pit, considering the consistency with the calculation method of the floating amount caused by the tunnel construction, this paper uses the Pasternak foundation model to calculate the deformation of the existing tunnel under the additional load and the Pasternak foundation model can simulate the shear force between the soil springs and the continuity of the deformation; the calculation results are more accurate. The total uplift of the tunnel can be obtained by superposition of the vertical deformation of the tunnel obtained by the two methods
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