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Chen H.,Beijing MTR Construction Administration Corporation | Zhang J.,BGI Engineering Consultants LTD.
Journal of Geomatics

An interval shield tunnel is located in a old town of beijing. It will pass through the old flat tile-roofed house longly. In order to grasp the rules of settlement and provide guidance for the subsequent construction, we choose a part of the area to test. Then the corresponding settlement of the section is carefully measured. We get the settlement data of different shield paramenters. The monitoring data is comprehensively analyzed, then general rules of settlement in the old flat tile-roofed house is summarized. This has important reference value for similar projects in future. Source

Jia Y.,Beijing Institute of Economics and Management | Liu W.,Beijing Jiaotong University | Li K.,Beijing MTR Construction Administration Corporation
Vibroengineering Procedia

A novel analytical model of vibration source for metro train based on "coupled vehicle and track basic unit" is established in this paper. The dynamic vehicle-track equations are completed with the displacement compatibility and the force equilibrium, and the model takes into account the infinite track structure, whole vehicle, track irregularity and wheel-rail Hertz contact. The special feature of track structure model is the periodical system of discrete supported sleepers, which converts the infinite integral equation into the combination in the wave number-frequency domain and simplifies the calculation progress. The rail dynamic responses and the wheel-rail contact force can be calculated easily. A complete software package TMCVT is programmed. A calculated example is achieved using the program. Compared the theoretical calculated results and the field tested results ,the coincidence with each other proved the analytical dynamic model for metro train coupled with vehicle and track is correct. © JVE International Ltd. Source

Chen T.,Beijing MTR Construction Administration Corporation | Xu R.,Tsinghua University | Li Q.,Tsinghua University
Acta Mechanica Solida Sinica

Abstract The effect of strain rate on the tensile strength of defective monocrystalline silicon (Si) nanorods is studied with the molecular dynamics method. The strain rate applied to the nanorods is varied from 107 to 1014 s-1, and the atomic interactions among the Si atoms are described by the Stillinger-Weber (SW) potential functions. The tensile strength of the ideal Si nanorod is shown to be strongly strain rate dependent and increasing with the strain rate. The failure pattern also shows strain rate dependence, indicating that increased strain rates gradually suppress unsuitable relaxation and dissipation mechanisms because of the accompanying larger external loadings. Furthermore, the effects of intrinsic material parameters (i.e., the cutoff radius of SW potential function) and defects (i.e., inevitable surface defects and internal preinstalled defects) are investigated. It is revealed that the effect of strain rate on the tensile strength of Si nanorod is influenced by both the intrinsic physical properties of the material and the distribution of the initial defects, with specific surface defects appearing to be more important to nanostructure design. © 2015 The Chinese Society of Theoretical and Applied Mechanics. Source

Li Y.,Beijing Jiaotong University | He P.,Beijing Jiaotong University | Qin D.,Beijing Jiaotong University | Qin D.,Beijing MTR Construction Administration Corporation
Zhongguo Tiedao Kexue/China Railway Science

Based upon the elastoplastic damage constitutive model of concrete, considering the discontinuity between the assembly block of shield segment and connecting bolts as well as the contact relationship between each assemble block, a 3D discontinuous contact computational model was built. Taking the shield tunnel project of certain metro in Suzhou for example, 3D discontinuous contact computational model was used to simulate the force condition of shield segment. Comparative analysis was conducted between the simulated results and those obtained by routine method model and modified routine method model respectively. Results show that the damage factor of some zones on the K assembly block at the vault in shield segment has exceeded the damage threshold value, and visible cracks thus appear on these zones. Plastic deformation appears on the inner side of shield segment top and bottom subjected to tension. The plastic zone depth of the K assembly block at shield segment top has reached 55% of the section width. The maximum internal force combination of shield segment locates at the joint of the haunch segment on both sides. 3D discontinuous contact computational model can better reflect the influence of segment joint on the internal force as well as the stress and deformation characteristics of concrete material for segment. The setup of the contact element at the joint of shield segment in the model has eliminated the influence on the calculation results by the diversity of the joint stiffness in other model. Both the compressive stiffness and the bending stiffness of shield segment will be affected. Source

Han Z.-W.,Beijing MTR Construction Administration Corporation | Dong J.,Beijing Sifang Automation Co | Tu L.-M.,Beijing Sifang Automation Co | Li H.-T.,Beijing Sifang Automation Co
Dianli Xitong Baohu yu Kongzhi/Power System Protection and Control

The deficiency of the metro direct-current feeder protection is mainly attributed to the application of single-ended current as the sole method in the detection and identification of breakdowns, which is time-consuming in case of remote short circuit and is very likely to fail or make mistakes. Therefore, by evaluating the distribution relationship between the side currents and line or load current, this paper proposes a segment domain protection method. Through this method, the protection measurement data at both sides of independent feed segment can be shared synchronously via optical fiber, and brand new protection criteria can be realized after a comprehensive domain processing. This paper presents the composition principles of independent feeder section and consequently proposes the "sum current" protection principle utilizing the sum of two ends' currents, impedance protection principle and double-ended tripping protection principle. In the end, approaches to realizing those protection principles are provided. The method can realize the entire DC feeder quick-action, which improves the speed, sensitivity and reliability of the Metro direct-current feeder protection. Source

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