Research On Dynamic Earth Pressure Acted On Marine Structures

As people speed up the exploration of resources in ocean,more and more infrastructures need to be constructed in deep water,including seabed pipeline for oil-gas transportation and mooring system for vessels.In the offshore industry,the most rapidly changing sector is that the movement of infrastructure is generally exceeding the size itself,which is differernt from traditional buildings on land.Conventional geotechnical approaches aim to make sure the stability of structures,which can not address particular features for a range of deepwater infrastructures.Dynamic earth pressure acted on moving structures is one of chanlleges needed to be solved.There are many factors influencing earth preassure acted on structures,including geometric shape of structrure,embedment depth,movement rate of structrure,and so on.To solve this problem,model tests are carried out to find out how earth preassure changes with different velocities of dragging plate and embedment depth of structrures.Also numerical model in DEM is built to simulate model test for further research.Research results and conclusions summarized as follows:1.Laboratory test shows development patterns of earth preassure acted on the moving plate remain the same with different dragging rates of plate.There are four stages: in the first stage,earth pressure slowly increases with the movement of plate;as soon as earth pressure enters the second stage,it increases rapidly to a certain value in short time;in the third stage,the rate of the growth declines,but earth pressure continues growth until it reaches the peak value;in the forth stage,earth pressure stops growing and keeps stable.Furthermore,with the same embedment depth,dynamic earth pressure acted on the plate increases with dragging rate of plate.While with the same dragging rate of plate,dynamic earth pressure increases as well with embedment depth.2.Rankine soil pressure theory is used to calculate the rest earth pressure and passive earth pressure acted on the plate,the results are compared with results got from model tests,which proves that conventional geotechnical approach is inapplicabile to solve this problem,thus discrete element method is introduced to solve this problem.Based on results got from tests and research achievements from other scholars,the rate factor and the deep factor of earth pressure acted on moving plate are found out.3.Based on model test,the 3D numerical model in DEM is built to simulate model test of dragging plate.The conclusions of numerical model are consistent with the results got from tests,which proves that DEM can well simulates the development of dynamic earth preassure acted on moving structres.4.The model in DEM proves that velocity of dragging plate and embedment depth determine dynamic earth preassure acted on moving structres in the process of dragging plate.