Abstract
This paper investigates the temporal-spatial characteristics of ground displacements as well as vertical and horizontal displacements and axial forces in existing piles induced by twin shield tunneling in clays. To that end, a case study and three-dimensional (3D) finite element (FE) analysis were performed. Based on the in situ monitoring data from the presented twin tunneling case history with existing piles beneath, the adopted 3D FE method was validated to be competent to yield reasonable simulation results. The validated 3D FE method was then used to analyze the effects of the distance between the tunnel and the pile, the distance between tunnel faces, and the pile length on the horizontal and vertical displacements and axial stresses in piles. It was found that the horizontal displacement distribution forms along the pile shaft for the front piles are similar to that for the back piles, whereas the magnitudes of the horizontal displacements of the front piles are slightly larger than that of the back piles. The interactions between piles in the pile group provide protection of the middle piles in the pile group against twin tunneling effects. With a reduction in the distance between the tunnel and the pile, the pile displacements and stresses increase nonlinearly. With an increase in the distance between tunnel faces, the maximum positive pile displacements and the maximum and minimum axial pile stresses increase, while the maximum negative pile displacements and the difference between the maximum and minimum axial pile stresses decrease.
Highlights
In congested urban cities, one of the effective means of relieving traffic pressure is to construct metros
The present study is targeted at investigating the ground surface settlements and pile group responses induced by twin tunneling in clays. 3D finite element analysis was performed to capture the development of ground surface settlements and pile group responses with advancing tunneling steps and to ascertain the effects of the distance between the tunnel and the pile, the distance between tunnel faces, and the pile length on the pile group responses on completion of tunneling
Ground surface settlements and pile group responses induced by twin tunneling in clays have been investigated by performing 3D finite element analysis validated with the in situ monitoring data
Summary
One of the effective means of relieving traffic pressure is to construct metros. This effect is dependent on factors such as the location of the pile relative to the tunnel, pile working load, cover-to-diameter ratio, and pile and tunnel dimensions [28] To better understand this vital issue, researchers have carried out numerous studies based on different methods such as field monitoring [29], theoretical analysis [30], numerical simulation [31], and experimental investigation [32]. The effects of twin tunneling in a thick clay stratum on ground movements and pile group responses have not been fully captured. The number of studies available into the effects of twin tunneling on ground movements and pile group responses is limited. The present study is targeted at investigating the ground surface settlements and pile group responses induced by twin tunneling in clays. The results obtained in this study have the potential to guide the protection of the pile group adjacent to twin tunneling
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