Simulation Analysis Of The Influence Of Negative Pore Water Pressure On Salvaging Of Submarine Falling Object

Adsorption force is an extremely important research content in marine geotechnical engineering,and it is also an unfavorable factor for the salvage of spacecraft,sunken ships and other falling objects.Therefore,it is a very key subject to study the negative pore water pressure variation of seabed muddy soil under uplift load.According to the interaction mechanism between the seabed falling objects and the surrounding muddy soil,this paper systematically expounds the composition of the adsorption force and its influencing factors.The finite element analysis software FLAC3 D is used to establish the model and select the parameters of the seabed soil and its falling objects.By analyzing the fishing results of falling objects under different uplift loads and mud depths,the optimal uplift load and the simulation value of the adsorption force of the falling objects are estimated,and the simulation value of the adsorption force is compared with the theoretical value,so as to illustrate the feasibility of the theoretical calculation formula of the adsorption force Sex.On this basis,the variation and contribution rate of the excess negative pore water pressure are obtained,and the effects of permeability,cohesion,internal friction angle and porosity,uplift load and velocity on the excess negative pore water pressure are further studied.The results show that: under different uplift loads and the same soil depth,the separation of falling objects from the bottom soil gradually develops from being close to the outer bucket wall to the inner bucket wall,until it is completely separated from the bottom soil.The final uplift displacement of the soil at the bottom of the falling object has nothing to do with the uplift load.At the same depth,the rising velocity and displacement of falling objects increase with the increase of uplift load,but the increase decreases.Under the same uplift load,the rising velocity and displacement of falling objects decrease with the increase of the depth of the mud;with the increase of the uplift load,the influence of seepage on the excess negative pore pressure firstly increases and then decreases,and the seepage reduces the excess negative pore pressure;when the same cohesive force and porosity is less than 0.5,the excess negative pore pressure increases with the increase of internal friction angle.When the same cohesive force and porosity is greater than 0.5,the excess negative pore pressure does not increase with the increase of internal friction angle;when the cohesion and internal friction angle are the same,the excess negative pore pressure decreases with the increase of porosity;when the same porosity and internal friction angle,the excess negative pore pressure increases with the increase of cohesion;under the same mud depth and uplift load,the excess negative pore pressure of soil increases with the increase of uplift speed,but when the uplift speed is the same and larger,the influence of uplift load on excess negative pore pressure is small.