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Numerical study on 3d effect and practical design in shield tunneling

Underground Space 2019年第3期4卷 201-209页

作者： Hossain Md.Shahin Teruo Nakai Tetsuo Okuno Islamic University of Technology GazipurBangladesh Geo-Research Institute Japan Nagoya Institute of Technology NagoyaJapan Shimizu Corporation TokyoJapan

In practice,different design methods are used in solving geotechnical problems depending on the type of issue such as the tunneling,braced excavation,or bearing capacity of a foundation,that is,the basic mechanism of the design method differs depending on the problems even for the same ground.A numerical analysis using the finite element method has recently become familiar owing to an improved computing performance;however,it is not widely used in the design of geotechnical problems including tunnel excavation owing to the reliability of the constitutive model of the ground *** a constitutive model of soils can properly express the properties of the ground material,a numerical analysis will play a vital role in solving the geotechnical *** this paper,the current state of a numerical analysis and its applicability in tunnel design are ***,the simulation of the ground behavior during tunnel excavation is carried out using sandy and clay ground parameters for shallow and deep tunnel *** paper is mainly focused on the effects of tunnel excavation under three-dimensional(3d)conditions,as well as the current design ***-linear 2d and 3d finite element analyses have been conducted,in which the elastoplastic sub-loading tij model has been used as a constitutive model of the *** performance and acceptability of the constitutive model have already been proven to reproduce the results of various model tests on different geotechnical problems such as the tunneling,braced excavation,and bearing capacity of a foundation,as well as the measured field *** was found that a 2d finite element analysis where the rate of stress release is considered,can be used for the prediction of the ground deformation and surface settlement;however,it does not provide rational information in the prediction of tunnel lining forces such as the stress,bending moment,and axial force,which emphasize the necessity of a 3d analysis with a proper cons

关键词： Shield tunneling Finite element analysis 3d effect

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3d effects on Vortex-Shedding Flow and Hydrodynamic Coefficients of A Vertically Oscillating Cylinder with A Bottom-Attached disk

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China Ocean Engineering 2017年第4期31卷 428-437页

作者： WANG Quan KOU Yu-feng ZHU Ren-qing CHEN Hong State Key Laboratory of Ocean Engineering Shanghai Jiao Tong UniversityShanghai 200240China Collaborative Innovation Center for Advanced Ship and deep-Sea Exploration Shanghai 200240China School of Naval Architecture and Ocean Engineering Jiangsu University of Science and TechnologyZhengjiang 212002China Shanghai Waigaoqiao Shipbuilding CO. LTD.Shanghai 200240China

Vortex-shedding flow induced by the vertical oscillation of a cylinder with bottom-attached disks of different diameter ratio dd/dc and thickness ratio td/dc is studied by a 3d （three-dimensional） numerical model developed in this paper, and compared with the results obtained through 2d （two-dimensional） numerical model. The high-order upwind scheme is applied to stabilize the computation, and convergence is accelerated by the multi-grid method. Qualitative and quantitative analyses of the differences between the 2d and 3d simulation results reveal the 3d effect on the flow field characteristics and hydrodynamic coefficients of the vertically oscillating cylinder with a bottom-attached disk. The 3d effect on the fluid field is mainly reflected in the significance of three vortex-shedding patterns： ωx has a greater effect on the flow fields around the sharp edges relative to the vortices generated in the 2d simulation. In the slice along the axial orientation, the vortex effect of ωy along the radial axis is smaller than that of ωx along the circumferential direction, indicating the radial effect on the velocity more pronounced than the circumferential effect around the sharp edges of the disk. The rotational interaction ωz of the fluid in the horizontal plane during the heave motion is insignificant. Based on the 2d and 3d simulation results, the turning points that separate the increasing regimes of the added mass coefficient and damping ratio are identified. The dependence of the turning point on the diameter ratio dd/dc and thickness ratio td/dc are discussed in detail.

关键词： 3d effect vortex-shedding pattern added mass coefficient damping ratio vertical oscillation

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3d STRESS LOCAL NONdESTRUCTIVE ANALYSIS IN THE MIddLE PLANE OF A PLATE

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Acta Mechanica Sinica 1998年第3期14卷 283-288页

作者：计欣华任伟陈金龙黄羽秦玉文 department of Mechanics Tianjin UniversityTianjin 300072China

The Isodyne technique based on the scattered light scanning from a thin laser beam can be used to obtain the information inside the loaded object at the room temperature nondestructively, so it is a very powerful technique in 3d stress analysis. The problems are how to interpret the information and how to get sufficient information from the few interference fringe. Birefringence phase shift technique can distinguish the fringe orders automatically and enrich the information in 256 gray levels between maxim and minim light intensity. The Isodyne birefringence phase shift method with an oblique incidence and equilibrium equation is presented, by which the 3d stresses in the middle plane of a plate with U shape notch are separated successfully. (Edited author abstract) 12 Refs.

关键词： 3d effect birefringence phase shift Isodyne technique oblique incidence

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