| Due to its easy construction,high durability,high stability,strong adaptability,strong scalability,and low pollution to the marine ecological environment,the plug-in cylindrical foundation has been widely used in offshore engineering.The penetration characteristics of the plug-in steel cylinder and its influence on adjacent cylinder bodies have important guiding significance for engineering practice.In this study,indoor model tests were conducted to investigate changes in steel cylinder penetration resistance under various factors,and the Coupled Euler-Lagrange(CEL)method was used to simulate the steel cylinder penetration process.The accuracy of the model was verified by comparing it with experimental data.Based on numerical simulation,soil uplift during the steel cylinder penetration process was analyzed,and a finite element model was established with adjacent cylinder bodies present to analyze the effect of different wall thickness steel cylinders on adjacent cylinder bodies.The following conclusions were drawn:(1)Model tests were conducted in different penetration velocities,wall thicknesses,cylinder diameters,water content conditions,and sandy soils.The results showed that the impact of penetration velocity on penetration resistance in dry sand was relatively small,while in wet sand,the penetration resistance slightly increased with the increase of penetration velocity;The penetration resistance increases with the increase of wall thickness or cylinder diameter,but the growth rate of penetration resistance gradually decreases with the increase of wall thickness,and the change is relatively small with the increase of cylinder diameter;Although the shear strength and internal friction angle of calcareous sand are greater than that of quartz sand,in actual tests,the penetration resistance of steel cylinder in quartz sand foundation is more extensive,which is mainly caused by the grain crushing characteristics of calcareous sand,which causes the decrease of sand compactness within a specific range at the end of steel cylinder;Normalized statistics were conducted on the bearing capacity coefficient N_q,and it was found that it first decreases and then increases with the increase of the cylinder diameter ratio.(2)After comparing the numerical calculation results with experimental values,the feasibility of simulating the steel cylinder penetration process using the CEL method was verified.Further analysis of the model results revealed that during the steel cylinder penetration process,the maximum uplift height of the soil inside the cylinder increased with the increase of penetration depth and wall thickness,but decreased with the increase of cylinder diameter.This is due to the different restrictions on the soil caused by different wall thicknesses and diameters of cylinder walls.The ratio of soil uplift volume inside and outside the cylinder decreases with the increase of penetration depth and cylinder diameter,and increases with the growth of wall thickness.The ratio of soil uplift volume inside and outside the cylinder is generally less than 1,but as the cylinder diameter decreases or the wall thickness increases,when both reach a specific value,the ratio of soil uplift volume inside and outside the cylinder will be greater than 1.(3)When there is an adjacent cylinder,the penetration of the steel cylinder has the greatest impact on the stress and displacement in the x-direction of the adjacent cylinder and the surrounding soil.This leads to an increase in stress and displacement levels in the x-axis direction of both,and the specific concentration position will also change correspondingly with the depth of penetration.Due to the presence of soil extrusion pressure,and the location and magnitude of the pressure change with the depth of penetration and wall thickness,the cylinder also experiences certain stress and displacement in the y and z-axis directions. |
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