FINITE ELEMENT ANALYSIS OF LOADING CHARACTERS OF GROUP PILES FOUNDATION DUE TO UNLOADING OF DEEP EXCAVATION

Large scale deep excavation is normally followed by construction of serried engineering piles inside the excavation zone，and unloading and rebound of soil induced by deep excavation have a great influence on those engineering piles． The mechanical characteristics of the pile groups in the bottom of foundation during the process of deep excavation were studied through building plane finite element model by ABAQUS software，and it was determined the lifting extent of pile block，pile-soil relative displacement，pile shaft force，and side friction of pile． Finally，each engineering pile was reloaded when excavation came to an end，then it was made judgments about their compressive bearing capacity and uplift bearing capacity according to the Q-s curve． The results showed that the bearing capacity of the engineering piles was related to their positions in the foundation excavation plane．