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Sun C.-J.,Beijing Jiaotong University | Sun C.-J.,Beijing Metro Construction Administration Co. | Zhang D.-L.,Beijing Jiaotong University | Liu J.-X.,Beijing MIDAS Co. | Cao X.-L.,Beijing MIDAS Co.
Yantu Gongcheng Xuebao/Chinese Journal of Geotechnical Engineering | Year: 2015

Wangjing station of Beijing metro line No.14 adopts the support system of underground diaphragm wall + steel support as well as diaphragm wall + steel support + anchor cable. The analysis of monitoring data shows that the influence range of excavation on the surrounding soil is close to the depth of foundation pit. The shapes of settling tank s of steel support section and mixed support section are different. The surface subsidence of mixed support section is larger than that of steel support section. In the mixed support section, when the excavation of foundation pit is shallow, the displacement of diaphragm wall is cantilever distributed. With the increase of excavation depth, the displacement is parabolic. The axial forces of first layer of steel strut are close to the work ones, and the tension of the lower anchor cable does not give full play. In the steel support section, the deformation of diaphragm wall presents rigid motion characteristics. The axial forces of steel support presenting stress relaxation and growing process have obvious effects of time and space. The axial forces of angle brace of steel support at shield well are quite gentle, the fluctuation is not large, and the spatial effects of structure are obvious. Two kinds of supporting system both can satisfy the requirements of deformation control indices of retaining structures. ©, 2015, Yantu Gongcheng Xuebao/Chinese Journal of Geotechnical Engineering. All right reserved. Source


Zheng X.,Beijing Jiaotong University | He P.,Beijing Jiaotong University | Zhang A.,Beijing Jiaotong University | Li Z.,Beijing Metro Construction Administration Co. | And 2 more authors.
Modern Tunnelling Technology | Year: 2015

This paper studies the influences of urban shield-driven tunneling on the stresses and displacements of adjacent bridge foundations with one, two or four piles using numerical methods. The results show that; 1) the axial stress of a single-pile foundation at the side nearest the tunnel decreases while that at the side farther away from tunnel increases, and the influence decreases with an increase of horizontal distance between the pile and tunnel; 2) the axial stress of a two-pile or four-pile foundation at the side nearest the tunnel increases while that at the side farther away from the tunnel decreases; 3) the influence of tunnel construction is greater on the group-pile foundation than on the single-pile foundation, for which the stress difference between the two sides at the top of the pile farther from the tunnel increases significantly after tunnelling, and concrete on the upper part of the pile farther away from the tunnel may be subjected to tensile stress when the pile cap is close to the tunnel; 4) the vertical displacement of the piles decreases with an increase of distance between pile and tunnel, and the settlement induced by tunnelling will be relatively small when the pile bottom is located below the tunnel floor; and 5) tunnelling has the greatest impact on the horizontal displacement of the top of a pile. Specifically, the horizontal displacement decreases linearly with an increase of pile depth when the pile is far from the tunnel, while it decreases nonlinearly when the pile is close to tunnel. The displacement at the upper part of the pile decreases rapidly with an increase of pile depth, and the displacement at the lower part converges to a constant, while the displacement at the top of the pile will peak at a certain distance between the pile and tunnel. ©, 2015, Editorial Office of "Modern Tunnelling Technology". All right reserved. Source


Sun C.,Beijing Jiaotong University | Sun C.,Beijing Metro Construction Administration Co. | Zhang D.,Beijing Jiaotong University | Guo Y.,Beijing Municipal Group | Ma X.,Beijing Metro Construction Administration Co.
Modern Tunnelling Technology | Year: 2015

Based on the construction practice of a large-diameter EPB shield first adopted for Beijing Metro Line 14, the building settlement induced by shield tunneling is predictied by numerical simulation and a comparative analysis of predicted and measured data is carried out. The results show that: the settlement and inclination of buildings are within control standards and the design and construction scheme is feasible; the settlement at the shield tail is 30% to 50% of the maximum settlement and it is a critical factor to control; the grouting via the embedded pipes on the ground is an effective auxiliary measure to control settlement; the key points to control settlement during shield construction include improvement of the plastic flow properties of the soil mass, control of driving parameters, extracted muck volume, simultaneous grouting at the shield tail, and secondary grouting. ©, 2015, Editorial Office of "Modern Tunnelling Technology". All right reserved. Source

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