Hydro-mechanical Coupled Analysis On Response Of Saturated Soil And Structure Subjected To Blast Loading

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.