波浪荷载作用下近海粉土动力特性研究

发布时间：2018-11-13 12:35

【摘要】：波浪荷载作用下海床土体中会产生孔隙水压力。当孔隙水压力累积到一定程度后,海床土体会出现液化和失稳破坏等行为。为更好地开发和利用海洋资源,需要加深波浪荷载下海床动力响应的研究,从而为近海地基土在动荷载下的动力特性和液化可能性以及海床与近海结构物地基稳定性的评判提供依据,这具有重要的理论和现实意义。在前人研究工作的基础上,本文通过理论和数值模拟相结合的方法对波浪荷载作用下海床土体的动力响应、动孔隙水压力的累积和发展规律、海床液化规律及其影响因素等进行了一系列研究工作,其主要成果如下：(1)扼要概述国内外关于波浪荷载作用下海床土体动力响应相关的研究成果和研究方法；了解粉土的定义及性质、土体液化的形式及其判断准则等；(2)首先简要介绍了势波理论及其求解、线性波的特征和波浪-海床的相互作用；接着扼要介绍了土介质中波的概念和特征,并对孔隙水压导致海床液化的可能性进行分析；(3)采用解析法求解平面应变条件下的Biot波动方程,结合边界条件推导出稳态波浪荷载作用下海床土体的应力、变形和孔隙水压力,并通过数值算例分析波浪-海床参数对海床地基土动力响应的影响；(4)采用有限差分Flac3D分析软件对波浪荷载作用下海床的动力特性进行数值模拟与分析,分析了波浪荷载作用下土体的动应力-动变形特性、总应力、孔隙水压力、有效应力的变化规律,探讨了海床土体的液化情况,分析水深、周期、波高对近海粉土抗液化能力的影响。结果表明：①粉土海床在波浪荷载作用下孔隙水压力累积现象比较明显。孔压累积引起孔隙水压力的增大和有效应力的减小。当有效应力减小到零时土体出现液化现象；②在其他条件相同的情况下,波高越大,累积孔压越大且液化深度越大；周期越长,波长、波压力、波速越大,且液化深度越大。③水深大小影响海床中孔压的累积并影响液化深度,在同等条件下随水深增加液化深度先增加后减小。
[Abstract]:The pore water pressure will be produced in the seabed soil under wave load. When pore water pressure accumulates to a certain extent, the behavior of liquefaction and instability occurs. In order to develop and utilize marine resources better, it is necessary to deepen the research on the dynamic response of ocean bed under wave loads. Therefore, it is of great theoretical and practical significance to provide the basis for the evaluation of the dynamic characteristics and liquefaction possibility of the offshore soil under the dynamic load, as well as the stability of the seabed and the offshore structure foundation. On the basis of previous research work, the dynamic response of seabed soil under wave loads and the accumulation and development of dynamic pore water pressure are studied by combining theory with numerical simulation. A series of research work has been done on the law of seabed liquefaction and its influencing factors. The main results are as follows: (1) the research results and research methods related to the dynamic response of the seabed soil under wave loads are summarized briefly at home and abroad; The definition and properties of silt, the form of soil liquefaction and its judgment criteria are understood. (2) the theory of potential wave and its solution, the characteristics of linear wave and the interaction between wave and seabed are introduced briefly. Secondly, the concept and characteristics of wave in soil medium are briefly introduced, and the possibility of liquefaction of seabed caused by pore water pressure is analyzed. (3) the Biot wave equation under plane strain condition is solved by analytical method, and the stress, deformation and pore water pressure of seabed soil under steady wave load are deduced in combination with boundary conditions. The influence of wave-seabed parameters on the dynamic response of seabed soil is analyzed by numerical examples. (4) numerical simulation and analysis of the dynamic characteristics of the seabed under wave load are carried out by using finite difference Flac3D software. The dynamic stress-dynamic deformation characteristics, total stress and pore water pressure of soil under wave load are analyzed. The effect of water depth, period and wave height on the liquefaction resistance of offshore silt is analyzed. The results show that: 1 the accumulation of pore water pressure on silt seabed under wave loads is obvious. Pore pressure accumulation results in the increase of pore water pressure and the decrease of effective stress. When the effective stress is reduced to 00:00, liquefaction occurs in the soil. 2 under the same conditions, the higher the wave height, the greater the accumulated pore pressure and the greater the liquefaction depth. The longer the period, the greater the wave pressure and velocity, and the greater the depth of liquefaction. 3 the depth of water affects the accumulation of pore pressure in the seabed and the depth of liquefaction. Under the same conditions, the depth of liquefaction increases first and then decreases with the increase of water depth.
【学位授予单位】：浙江工业大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TU435

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