Abstract
The expansion of urban underpass has become the mainstream of development to cope with urban congestion, and the effect on adjacent existing structures during enlarging construction is also an important issue in the construction process. In order to better understand the influence of tunneling on adjacent structures, the pedestrian underpass expanding project above-crossing Xi’an Metro Line 1 was investigated. The aim was to analyze the deformation curves characteristics of adjacent structures by field observation of ground settlement, heave of existing tunnels, and settlement of piles. The results show that the ground settlement curve in the vertical direction of the underpass is similar to the shape of V, and the maximum settlement appearing in the center line of underpass is 18.7 mm. Due to the effect of existing tunnels on the ground deformation, the settlement curve in the parallel direction of the underpass is similar to the shape of M. Above-crossing tunneling would cause the existing tunnels to heave, and the heave mainly occurs in the range of −6 m to 12 m between the pedestrian tunnel face and the center line of each tunnel. The heave curve is similar to the shape of inverted U. The settlement of piles is linear with its axial stress and significantly affected by its location. The settlement curve of piles is similar to the shape of S in two dimensions. On the basis of deformation curves, this paper presents some equations to describe the shape of V, M, inverted U, and S, respectively, by the inverted Gaussian distribution curve, superimposed Gaussian distribution curve, Gaussian distribution curve, and arctangent function.
Highlights
Due to the demand of urban construction and highly congested urban, an increasing number of tunnels are being or have been constructed adjacent or above existing tunnels or building foundation to meet the increasing requirement of transportation
It is widely reported that the settlement curve for a single tunnel takes the shape of an inverted Gaussian distribution curve symmetrical to the tunnel axis at right angles [15]
Based on the case of Xi’an underpass expanding project abovecrossing Metro Line 1, this paper studies the e ect of rectangular tunneling on the deformation of adjacent structures through a large number of measured data and analyzes the deformation law. e aim was to provide experience and basis for similar projects in the future
Summary
Due to the demand of urban construction and highly congested urban, an increasing number of tunnels are being or have been constructed adjacent or above existing tunnels or building foundation to meet the increasing requirement of transportation. Choi and Lee [26] carried out a series of physical model tests to investigate the various factors which a ect the mechanical behavior of the existing and new tunnels during the excavation. Ng [44] carried out a series of threedimensional centrifuge model tests to study the e ects of twin tunneling activity on existing single pile and found that the settlement of pile induced by excavation is closely related to the relative depth of pile. Based on the case of Xi’an underpass expanding project abovecrossing Metro Line 1, this paper studies the e ect of rectangular tunneling on the deformation of adjacent structures through a large number of measured data and analyzes the deformation law. Based on the case of Xi’an underpass expanding project abovecrossing Metro Line 1, this paper studies the e ect of rectangular tunneling on the deformation of adjacent structures through a large number of measured data and analyzes the deformation law. e aim was to provide experience and basis for similar projects in the future
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