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Zhang Z.-G.,Shanghai University | Zhang Z.-G.,Tongji University | Zhang Z.-G.,Shanghai Institute of Applied Mathematics and Mechanics | Zhang M.-X.,Shanghai University | Wang W.-D.,East China Architecture Design and Research Institute
Yantu Lixue/Rock and Soil Mechanics

Unloading of foundation pit excavation will no doubt induce the soil deformation and have result in uneven settlements of adjacent metro tunnels. The excessive settlements may induce the crack of tunnel segments and eventually may affect the safety use of metro trains. Two-stage method is presented for determining the longitudinal deformation of metro tunnels caused by adjacent foundation pit excavation. The soil unloading effects of the bottom plan and the surrounding walls induced by the foundation pit excavation can be considered by this method. Firstly the additional stress due to adjacent foundation pit excavation is calculated. Secondly the governing differential equation is built up based on Winkler model. Then the differential equation is deduced to the finite element equation by the Galerkin method; and vertical displacement and internal forces along longitudinal axis are obtained. Furthermore, the parametric analysis of existing tunnels is carried out; such as, the different depths, the distance from the excavation site, the different geologic conditions and the different outer diameter of the tunnel. Finally, the results from present approach are compared with that from 3D numerical simulation and measured data; good agreement is obtained. It may provide certain basis to draw up correctly protective measures of metro tunnels influenced by adjacent excavation. Source

Wang K.,Tongji University | Wang K.,AECOM Technology Corporation | Tong L.-W.,Tongji University | Zhu J.,Tongji University | And 6 more authors.
Journal of Bridge Engineering

The welded truss composed of circular hollow section (CHS) braces and concrete-filled circular hollow-section (CFCHS) chords is a new kind of structural system that has been increasingly applied in large span arch bridges in China. It is necessary to have a good knowledge of fatigue strength of the welded CHS-to-CFCHS joints for the design of this kind of composite bridge. This paper reports on a series of tests on welded CHS-to-CFCHS T-joints subjected to axial cyclic fatigue loading in the brace. Eleven joints were designed to investigate various influence factors such as different nondimensional geometric parameters of circular hollow sections and different concrete strength grades. The quality of welds connecting brace and chord members were examined using the magnetic particle and radiographic inspection methods. The conditions of hot spot stress at both the crown and saddle positions in brace and chord members were determined by means of linear and nonlinear extrapolation methods. During the fatigue testing process, the number of cycles relating to several stages of failure, the crack initiation positions, crack propagation patterns, and the final failure modes were recorded. Fatigue strength of the CHS-to-CFCHS T-joints was compared with that of CHS-to-CHS T-joints. It is concluded that the CHS-to-CFCHS T-joints have a much lower stress concentration factor and consequently have better fatigue strength than the CHS-to-CHS T-joints, when both kinds of joints have the same nondimensional geometrical parameters and same nominal stresses on the brace. The Srhs-Nf curves in the Comité International pour le Développement et l'Étude de la Construction Tubulaire guidelines used for CHS-to-CHS joints are not appropriate for the reliable fatigue assessment of CHS-to-CFCHS T-joints based on the current test data. © 2013 American Society of Civil Engineers. Source

Chen Y.-C.,East China Architecture Design and Research Institute
Yantu Gongcheng Xuebao/Chinese Journal of Geotechnical Engineering

Both the TRD construction method and dual-purpose wall method are newly developed retaining techniques for excavations. Adjacent to the excavation of Nanjing Ecological Park, there are several streets, a metro station, tunnels and a lot of municipal pipelines. The general information of the project and the design work of the deep excavation are introduced. In particular, the details of the TRD construction method used for protecting the metro station and the dual-purpose wall method adopted for energy saving purpose are introduced. The field monitoring results on the performance of the excavation are discussed as well. With the help of these new techniques, the excavation has been successfully completed. The monitoring results show that the influences of the excavation on the adjacent environments are limited by using the TRD construction method and dual-purpose wall method. ©, 2015, Yantu Gongcheng Xuebao/Chinese Journal of Geotechnical Engineering. All right reserved. Source

Zhao T.,Tianjin Innovative Finance Investment Co. | Yang H.-S.,Tianjin Innovative Finance Investment Co. | Wang X.-J.,East China Architecture Design and Research Institute
Yantu Lixue/Rock and Soil Mechanics

There is a great development of underground space in the Yujiapu area, in Tianjin. The problem of anti-float is serious, because of the buried depth of the basement is deep and the groundwater table is higher. The monolayer area is about 30,000 m2; and the buried depth of the basement is about 16 m. Based on the Yujiapu north-south underground garage, the tests on pedestal uplift piles and side-grouting uplift piles are canied out. The tests show that, compared with the normal uplift piles, the pedestal uplift piles and side-grouting uplift piles have advantages of greater uplift bearing capacity and shorter pile length; so that its economic benefit is notable. The pedestal pile is better than the side-grouting piles in the aspects of ultimate bearing capacity and displacement controlling. The pedestal uplift pile is used in the garage; full hydraulic swivel-driven construction technology is used too. The successful using of the pedestal uplift piles has great significance and practical engineering value; it will be a good practical case for similar projects. ©, 2014, Academia Sinica. All right reserved. Source

Li J.-J.,East China Architecture Design and Research Institute | Wang W.-D.,East China Architecture Design and Research Institute | Huang M.-S.,Tongji University | Fu K.,Tongji University
Yantu Gongcheng Xuebao/Chinese Journal of Geotechnical Engineering

According to the influence problems of piles induced by the crossing No. 2 and No. 4 shield tunnels in the west terminal of Shanghai Hongqiao Comprehensive Transportation Hub, the two phrase analysis methods simplify analysis method and displacement controlled FEM method are used in the analysis of the influence of piles of structure induced by the crossing tunnels, single tunnel or multi-tunnels. The special design measures using the displacement controlled FEM in the analysis of multi-tunnels are put forward according to the analysis results. The in-situ monitoring results of construction stage certify the validity of the design measurements. Source

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