【作者】 王亚光；

【导师】 王建华； 叶冠林； 廖晨聪；

【作者基本信息】 上海交通大学 ， 土木工程， 2019， 博士

【摘要】 爆炸作用下的饱和土-结构物的耦合机制影响因素多而复杂,其分析涉及了多孔介质渗流力学、爆炸动力学、土动力学等多学科内容。由于爆炸条件下的水土耦合求解非常困难,在研究饱和土中爆炸波传播及爆炸条件下土-结构相互作用时普遍忽略孔隙水压力作用,考虑流固耦合作用的饱和土动力响应及饱和土中结构物动力响应的研究成果较少,非线性荷载下岩土材料参数难以确定,现有的土中爆炸经验公式应用范围较小。因此,研究考虑流固耦合作用饱和土与结构物的动力响应,对土中结构物的抗爆性能评估具有重要意义。本文采用理论研究和数值分析等方法,研究了考虑流固耦合作用的饱和土与结构物在爆炸荷载下的动力响应问题。提出了融合流固耦合理论及材料动力参数反演的饱和土爆炸响应数值分析方法;建立考虑流固耦合作用的饱和土爆炸响应模型;基于遗传算法进行了岩土动力参数最优化分析,探讨海床中爆炸波的传播规律;从土-水-结耦合作用出发,分析爆炸荷载下海洋结构物的动力响应。主要研究内容和成果如下:(1)提出了融合流固耦合理论及材料动力参数反演的饱和土爆炸响应数值分析方法。建立了基于u-p模型饱和土爆炸响应模型,采用了AMALGAM遗传算法的实现材料动力参数反分析,对爆炸条件下的多孔介质材料参数进行了最优化求解,在Matlab和LS-DYNA平台上实现了岩土动参数反分析,并形成了Pareto最优解集。研究表明爆炸荷载下考虑流固耦合作用的饱和土瞬时刚度提高,爆炸瞬间的不排水条件使得孔隙水和土体骨架共同承担爆炸能量。(2)建立了饱和黏土海床爆炸响应模型及饱和砂性土海床爆炸响应模型,阐明了特定土质海床中的爆炸波衰减规律,提出了任意起爆当量和起爆距离条件下的应力峰值和孔压峰值的经验预测公式。研究表明砂性土海床中爆炸应力波衰减速率明显快于黏性土海床,其应力峰值呈指数衰减,而孔压峰值由于砂性土的剪胀性和渗透条件更好呈近似线性衰减;饱和黏土海床中的应力峰值和孔压峰值均呈指数衰减,且衰减速率慢于饱和砂性土海床。基于大量参数分析,提出了爆炸荷载下饱和海床中应力峰值和孔压峰值衰减规律的经验预测公式,并进行了数值模拟验证。(3)建立了考虑饱和海床-管线-海水耦合作用的动力响应模型,研究了海洋管线在侧向海底爆炸荷载下的动力响应,对起爆当量、起爆距离、管线埋深、管线直径及壁厚等参数进行了分析。研究结果表明爆炸荷载作用下,半埋管线在水中及土中爆炸波的共同作用下稳定性最差,且海床的部分约束降低了结构抗爆能力强调了饱水环境下管壁厚度对于结构稳定的重要性,建议对管线浅埋提高结构的抗爆能力,且埋深不低于1.5倍直径。开展了饱和土动力响应模型与单相介质模型的数值对比实验,发现采用忽略孔隙水的单相介质模型分析饱和土中结构物的动力响应,管线位移响应被低估30%、应力响应被低估20%、管周土的应力响应被低估30%。(4)建立了考虑饱和海床-大直径钢管桩-海水-空气耦合作用的动力响应模型,研究揭示了不同起爆当量和爆炸深度条件下钢管桩基础的位移和应力响应模式。研究结果表明近海底爆炸发生在海床中时,结构响应更大。建立了对比分析模型,考虑桩顶荷载对于结构动力响应的影响,桩顶荷载的施加降低了结构的响应速率,但对于高宽比较大的壳体结构,需要考虑侧向冲击荷载下的重力二阶效应,建议采用本文模型进行海洋结构物爆炸响应分析。更多还原

【Abstract】 Hydro-mechanical coupling effect of saturated soil subjected to blast loading involves seepage flow mechanics,dynamics of explosion,soil dynamics,etc.and relates to various influence factors and complicated conditions.There is few research about blast response of saturated soil and structures considering the effect of pore water due to the difficulty of solving fluid-solid coupling.It is difficult to determine the soil parameters under non-liner load.And application of the existing formulas is limited.Therefore,blast response analysis of saturated soil-structure is of great significance for evaluation of structural anti-explosion capacity.A numerical method fusing the fluid-solid coupling and soil dynamic parameter optimization is proposed in this thesis based on theoretical research and finite element method.Blast response of saturated soil considering pore water effect is discussed from the perspective of blast wave propagation in the saturated soil;the geotechnical material parameters is determined and the soil dynamic characristics is analyzed via the application of genetic algorithm into soil dynamics;blast response of structures in the saturated soil is analyzed considering fluid-structure interaction and hydro-mechanical coupling effect.Main researches and achievements are summarized as follows:(1)A numerical method fusing the fluid-solid coupling and soil dynamic parameter optimization is proposed in this thesis.And a hydro-mechanical model is established by integrated the u-p model into FEM to simulate the interaction of pore water and soil skeleton.The AMALGAM algorithm based on Parato front is adopted to optimize dynamic parameter of porous media.The optimization of soil parameters under blast loading is carried out on interface of Matlab and LS-DYNA.The Parato front is obtained after back analysis of soil parameter.Based on the optimization results,the mechanism of soil stiffness enhancement is revealed.Interaction of solid and pore water will lead to the combined effort of solid and pore water to bear blast loading.(2)In allusion to deficiency of marine soil mechanics research and limited applicability of the available empirical formulas,a three-dimensional numerical model for saturated soil response induced by underwater explosion in marine environment is developed to investigate blast wave propagation in sandy bed and clayey bed.Attenuation formulas of peak pressure and EPWP is proposed contain arbitrary explosion equivalent and stand-off distance,which is verified by numerical experiments.The various mechanism of decay modes for the peak EPWP is revealed.The research carried out in this paper indicates that the peak EPWP and peak pressure attenuates expontially in the clayey seabed.While the peak pressure attenuates expontially and peak EPWP decays linealy in the sandy seabed.Generally,decay rates of the blast wave in the clayey seabed is greater than that in the sandy seabed.(3)A comprehensive hydro-mechanical model is presented to investigation dynamic response of submerged pipelines subjected to underwater explosion.In the proposed model,Fluid-Structure Interaction(FSI)and Pipeline-Seabed Interaction(PSI)are studied simultaneously based on numerical technique.A systematic parametric study is conducted to investigation effect of embedment depth,TNT equivalent,stand-off distance,pipeline diameter and pipeline thickness to blast response of the submerged pipelines.The significance of pipeline thickness to structural stability is highlighted.And the burial depth for the submarine pipeline is suggested to be larger than 1.5 times the pipline diameter to enhance the structural anti-explosion capacity.In order to explore the pore water effect in the interaction of structures and saturated soil,comparative experiments are carried out between the hydro-mechanical model and the single-phase model.Displacement response and stress response of pipeline are underestimated by 30% and 20% respectively when ignoring the pore water in the soil.The soil response in the single-phase model is underestimated by 30%,which indicates the significance of fluid-solid coupling.(4)A hydro-mechanical model considering the coupling effect of soil,water,air and structure is established to investigate the dynamic response of mono-pile foundation due to underwater explosion.Dynamic response of the pile foundation is illustrated via numerical calculation.The research work in this paper indicates that the pile foundation responses more fiercely when underwater explosion takes place near the seabed.A comparative model is established to discuss effect of head boundary to the pile response.The secondary-order effect of the pile foundation under blast loading is worthy of attention.The anti-explosion capacity of marine structures is suggested to be evaluated based on the hydro-mechanical model presented in this paper.更多还原