桩-土界面软化和基坑开挖对抗拔桩影响分析OA

The uplift pile,which resists upward loads,is extensively used in coastal buildings.Its bearing performance is affected by factors such as pile-soil interface softening and foundation pit excavation.Reasonably determining the bearing performance of uplift piles is essential for engineering construction.The relative displacement between the pile and soil is divided into two components:the slip displacement at the pile-soil interface and the vertical displacement of the side soil.A cohesive zone model is introduced in the slip zone to represent the softening behavior of the interface.The vertical displacement of the side soil consists of elastic rebound and shear displacement calculated using Randolph's shear displacement method.Based on the principles of pile load transfer and displacement continuity,a displacement compatibility method incorporating boundary conditions is adopted and solved iteratively to obtain the axial force distribution along the pile,the pile side friction resistance,and the load-displacement curve.Moreover,it is validated through numerical case analyses and in-situ tests on uplift piles.The analysis results indicate the follows:the rebound-induced displacement field caused by foundation pit excavation leads to passive uplift of the pile;some portions of the pile side friction resistance reach peak strength prematurely and then soften,resulting in reduced bearing performance after excavation;excavation depth,effective pile length,and soil properties all affect the bearing performance,where deeper excavation shows a greater impact,while longer effective pile length helps mitigate the adverse effect.The in-situ test results indicate the following:the uplift displacement of the pile at the design load after foundation pit excavation increases significantly,compared to that before excavation.The uplift performance predicted by this method after foundation pit excavation shows small deviation from the measured results,and can serve as a reference for engineering design.