Abstract
Tunnels are often preferred for underground transportation in densely populated areas. In these areas, it is almost inevitable for tunnels to run close to some existing pile foundations. Since tunnelling activities induce stress relief and soil movement in the ground, existing piles may suffer from additional axial and lateral forces, bending moments, settlements and lateral deflections. Most of the previous researches on the responses of pile foundations due to tunnel construction were carried out under the plane strain condition. In this paper, a three-dimensional, elasto-plastic and coupled-consolidation finite element parametric study has been carried out to investigate the effects of a 6 m open-face advancing tunnel on a two by two pile group in saturated stiff clay. The influence of different cover-to-diameter (C/D) tunnel ratios (namely 2.0, 2.5 & 3.0) was studied. The objectives of this study are to determine the changes in axial load distribution, changes in shaft resistance along the shaft of pile group and settlement of pile cap due to an advancing open-face tunnel.
Highlights
A piled foundation transfers the load of the structure into the ground, generating stresses in the surrounding soil
When the tunnel is excavated at C/D=2.0, it causes the reduction of shaft resistance in both the front (P1) and rear (P2) piles and load transfers from front pile to rear pile
This leads to an increase in base load by 60% and 32% in the front and rear piles, respectively
Summary
A piled foundation transfers the load of the structure into the ground, generating stresses in the surrounding soil. Tunnel excavation induces stress relief to the surrounding soil and results in ground movements around the tunnel, which propagate through the soil to the ground surface. Since tunnel construction inevitably induces soil movement and stress changes in the ground, it may cause additional settlement and tilting to nearby existing piled foundations. To understand the pile–soil–tunnel interaction mechanism, many researchers have conducted field monitoring studies and centrifuge model tests [1,2,3,4,5,6,7,8,9]. The magnitudes of which likely depended on the relative locations of tunnels and piles
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