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海洋岩土工程中的大变形数值模拟

海洋岩土工程中的大变形数值模拟

On the instability of offshore foundations: theory and mechanism

中国力学大会-2015

作者：王栋 Centre for Offshore Foundation Systems The University of Western Australia

针对具体工程背景,介绍在3种数值计算方法上的最新进展,进而讨论3种方法的计算精度、计算效率和适用范围.

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Science China(Physics,Mechanics & Astronomy) 2015年第12期58卷 125-141页

作者： GAO FuPing LI JinHui QI WenGang HU Cun Institute of Mechanics Chinese Academy of Sciences Centre for Offshore Foundation Systems University of Western Australia

As the offshore engineering moving from shallow to deep waters, the foundation types for fixed and floating platforms have been gradually evolving to minimize engineering costs and structural risks in the harsh offshore environments. Particular focus of this paper is on the foundation instability and its failure mechanisms as well as the relevant theory advances for the prevailing foundation types in both shallow and deep water depths. Piles, spudcans, gravity bases, suction caissons, and plate anchors are detailed in this paper. The failure phenomena and mechanisms for each type of foundations are identified and summarized, respectively. The theoretical approaches along with sophisticated empirical solutions for the bearing capacity problems are then presented. The major challenges are from flow-structure-soil coupling processes, rigorous constitutive modeling of cyclic behaviors of marine sediments, and the spatial variability of soil properties for large-spreading structures. Further researches are suggested to reveal the instability mechanisms for underpinning the evolution of offshore foundations.

关键词：海洋沉积物不稳定性失稳机理基础结构风险土壤性质空间变异性海上工程

Failure mechanisms of a spudcan penetrating next to an existing footprint

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Theoretical & Applied Mechanics Letters 2015年第2期5卷 64-68页

作者： Vickie Kong Mark J.Cassidy Christophe Gaudin Fugro-Advanced Geomechanics Centre for Offshore Foundation Systems and ARC CoE for Geotechnical Science and Engineering University of Western Australia

Reinstallation of mobile jack-up rigs next to existing footprints is a problematic operation because the spudcan located near the footprints is subjected to eccentric and/or inclined loading conditions. Geotech- nical centrifuge studies have measured these loads for combinations of changing footprint geometry, footprint soil properties and the offset of the reinstallation from the footprint centre. These tests have been of full model spudcans in order to accurately measure the combined loads developed. They have not provided information on the mechanisms of failure occurring during this complex installation. Ob- servations from a visualisation test, where a half spudcan is penetrated against a transparent window in a geotechnical centrifuge, are reported in this paper. The mechanisms of failure at different stages during the nenetrntirm are nr^nted

关键词： Jack-up Footprint Combined loading Spudcan offshore geotechnics

FLOW-PIPE-SEEPAGE COUPLING ANALYSIS OF SPANNING INITIATION OF A PARTIALLY-EMBEDDED PIPELINE

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Journal of Hydrodynamics 2010年第4期22卷 478-487页

作者： GAO Fu-ping LUO Cheng-cai Key Laboratory for Hydrodynamics and Ocean Engineering Institute of Mechanics Chinese Academy of Sciences Beijing 100190 China Centre for Offshore Foundation Systems The University of Western Australia Nedlands WA 6907 Australia

The initiation of pipeline spanning involves the coupling between the flow over the pipeline and the seepage-flow in the soil underneath the pipeline.The pipeline spanning initiation is experimentally observed and discussed in this article.It is qualitatively indicated that the pressure-drop induced soil seepage failure is the predominant cause for pipeline spanning initiation.A flow-pipe-seepage sequential coupling Finite Element Method（FEM） model is proposed to simulate the coupling between the water flow-field and the soil seepage-field.A critical hydraulic gradient is obtained for oblique seepage failure of the sand in the direction tangent to the pipe.Parametric study is performed to investigate the effects of inflow velocity,pipe embedment on the pressure-drop,and the effects of soil internal friction angle and pipe embedment-to-diameter ratio on the critical flow velocity for pipeline spanning initiation.It is indicated that the dimensionless critical flow velocity changes approximately linearly with the soil internal friction angle for the submarine pipeline partially-embedded in a sandy seabed.

关键词： submarine pipeline pipeline spanning seepage failure flow-pipe-seepage coupling

Assessment of pipeline stability in the Gulf of Mexico during hurricanes using dynamic analysis

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Theoretical & Applied Mechanics Letters 2015年第2期5卷 74-79页

作者： Yinghui Tian Bassem Youssef Mark J.Cassidy Centre for Offshore Foundation Systems and ARC CoE for Geotechnical Science and Engineering University of Western Australia Atteris Level 3220 St Georges TerracePerthWA6000Australia

Pipelines are the critical link between major offshore oil and gas developments and the mainland. Any inadequate on-bottom stability design could result in disruption and failure, having a devastating impact on the economy and environment. Predicting the stability behavior of offshore pipelines in hurricanes is therefore vital to the assessment of both new design and existing assets. The Gulf of Mexico has a very dense network of pipeline systems constructed on the seabed. During the last two decades, the Gulf of Mexico has experienced a series of strong hurricanes, which have destroyed, disrupted and destabilized many pipelines. This paper first reviews some of these engineering cases. Following that, three case studies are retrospectively simulated using an in-house developed program. The study utilizes the offshore pipeline and hurricane details to conduct a Dynamic Lateral Stability analysis, with the results providing evidence as to the accuracy of the modeling techniques developed.

关键词： Pipeline On-bottom stability Dynamic lateral stability analysis Force-resultant model Hydrodynamic load

Observed response of maglev structure undercrossed by three shield tunnels in soft soil

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Underground Space 2022年第4期7卷 636-661页

作者： Dong-Mei Zhang Xiao-Chuang Xie Zhong-Kai Huang Mao-Zhu Peng Hong-Xin Zhu Key Laboratory of Geotechnical and Underground Engineering Ministry of EducationTongji UniversityShanghai 200092China Department of Geotechnical Engineering College of Civil EngineeringTongji UniversityShanghai 200092China Centre for Offshore Foundation Systems University of Western Australia35 Stirling HighwayCrawleyPerthWA 6009Australia Shanghai Municipal Engineering Design Institute(Group)Co. Ltd.China

This paper investigates the response of a maglev structure to three under-crossing tunnels of the Shanghai Metro Line 13.The minimal distance between the tunnels and pile groups of the maglev structure is only 1.5 m,thus the deformations of the maglev structure are strictly controlled for the serviceability of the operating maglev trains.The displacements of maglev piers and ground settlements during different tunnelling stages are monitored with an automatic measuring system.Based on the observed data,the ground settlement trough and displacements of maglev piers caused by the three shield tunnelling procedures are analyzed and discussed.The maximal ground settlement after the completion of the three tunnelling procedures is -43 mm.To operate the existing maglev safely,practical construction control methods are applied,including synchronous grouting,adjustment of the shield status,shield-advancing speed control,and stabilisation of the soil chamber pressure.With these countermeasures,the tunnel-induced deformations of maglev piers are well below the predefined thresholds.All piers heave under the strict deformation criterion of 2.0 mm.The crossing project is finally completed without interruptions of the maglev operations by monitoring the progress.The presented project is a valuable example for the evaluation of shield tunnelling effects on the adjacent maglev structures and establishes criteria for similar projects in the future.

关键词： Maglev Multi-crossing Shield tunnelling Ground settlement Pier displacement

Editorial:Special issue on offshore structure-soil interaction

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Theoretical & Applied Mechanics Letters 2015年第2期5卷 63-63页

作者： Fu-Ping Gao Mark J.Cassidy Key Laboratory for Mechanics in Fluid Solid Coupling systems Institute of MechanicsChinese Academy of Sciences Centre for Offshore Foundation Systems and ARC CoE for Geotechnical Science and Engineering University of Western Australia

As the offshore industries move from shallow to deep waters in excess of 1000 m, there has been rapid development of ocean engineering practices. Innovations in theoretical and applied me- chanics have been essential in this shift and in underpinning the exploitation of offshore oil and gas and renewable energy re- sources worldwide. Understanding and predicting physical mech- anisms of structure-soil interactions are vital for the stability and safety of offshore engineering structures. Accordingly, in this spe- cial issue of Theoretical ＆ Applied Mechanics Letters （TAME）, eight letter-papers are published to present recent advances in analyti- cal and numerical analysis and in physical modeling of offshore structure-soil interactions in marine environments. They all provide examples of how enhanced understanding of mechanics can imoact on aoDlied oroiects.

关键词： soil Editorial

The Use of Force-Resultant Models of Shallow foundations in offshore Applications

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The Use of Force-Resultant Models of Shallow Foundations in ...

Numerical modelling rock deformation subject to nitrogen cooling to study permeability evolution

The Sixth World Congress on Computational Mechanics in Conjunction with the Second Asian-Pacific Congress on Computational MechanicsⅠ

作者： Mark Jason Cassidy Centre for Offshore Foundation Systems University of Western Australia 35 Stirling Highway Perth 6009 Australia.

Traditional approaches to geotechnical consideration of soil-structure interaction of shallow foundations have been based on beating capacity methods and the use of numerous ad hoc empirical factors. These theories are adequate(if somewhat conservative)in predicting failure. However, the important issues of predicting plastic strains and displacements pre-failure are usually neglected. Furthermore, difficulties in implementing them within structural analysis programs limit their applicability to many offshore applications, where the integrated assessment of fluid-structure-soil interaction in paramount.

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International Journal of Coal Science & Technology 2015年第4期2卷 293-298页

作者： Chunhui Zhang Laigui Wang Jianhua Du Yinghui Tian School of Civil Engineering Hebei University of Science andTechnology Shijiazhuang 050018 China School of Mechanics and Engineering Liaoning TechnicalUniversity Fuxin 123000 China Shijiazhuang Insitute of Railway Technology Shijiazhuang 050041 China Centre for Offshore Foundation Systems University ofWestern Australia Crawley WA 6009 Australia

How to model the permeability evolution of rock subjected to liquid nitrogen cooling is a key issue. This paper proposes a simple but practical method to study the permeability evolution of rocks subject to liquid nitrogen cooling. FLAC with FISH function was employed to numerically model the rock behavior under cooling. The enhanced permeability of the volumetric strain was defined, and the permeability was directly evaluated based on element’s volumetric strain. Detailed procedures for implementing the evolution model of permeability in this paper were presented. A case study was carried out to simulate a coal bed where liquid nitrogen was injected in the bore hole. And a semi-submerged test of liquid nitrogen was performed. The method to model the permeability evolution of rocks subject to liquid nitrogen shock in this paper was proved to be right by the test results. This simulation results are discussed with the hope to provide some insight into understanding the nitrogen cooling practice.

关键词： FLAC数值模拟冷却过程岩石变形液氮渗透性演化体积应变演化模型液体氮