The Bearing Behavior Analysis Of Loaded Piles In The Passive Area Of The Excavation

Further downward excavation beneath the existing building will affect the loaded engineering piles in the foundation pit.This type of engineering pile is subjected to large axial loads at the top of the pile,and will also affected by the lateral earth pressure caused by the excavation of the foundation pit,the unloading and the uplift of the soil in the pit.In this paper,we take the loaded engineering piles in the passive zone of the pit as our research object,to study the bearing and deformation characteristics of this type of piles in the process of coupling the axial load at the top of the pile and the lateral load at the bottom of the pile during the further downward excavation.(1) The indoor model test is used to simulate the conditions of the further downward excavation.We take control of the main two parameters:the axial load at the top of the pile "P"and the distance between the pile and the retaining structure "L",and carry out the model tests of single pile,two piles and nine piles separately to explore the bearing characteristics of them in different conditions.The test results show that the loaded engineering pile during the further downward excavation will occur lateral deformation,and the axial load at the top of the pile will generate additional bending moments and increase the lateral deformation;The smaller the distance between the engineering pile and the retaining structure,the more significant the lateral displacement of the soil will be.(2) We propose a simplified analytical method for the bearing characteristics of engineering piles in the passive zone,which coupling the axial load at the top of the pile and the lateral load at the bottom of the pile.Based on the p-y curve,we turn the displacement of the soil Ay into the earth pressure ?p which applied to the existing loaded engineering piles,and then established a simplified analytical method for the bearing characteristics of engineering piles in the passive zone to provide theoretical guidance for the analysis of the bearing characteristics of this type of engineering piles during further downward excavation beneath the existing building.(3) Based on the indoor model test results,and combined with PLAXIS 2D numerical model data,we verify the accuracy of the simplified analytical method.We compare and verify the results of the simplified analytical method with the model tests results and numerical simulation data separately to verify the accuracy of the simplified analytical method.After verifying the accuracy of the method,we select the axial load at the top of the pile "P",the distance between the pile and the retaining structure "L" and the excavation depth "H" to perform parameter analysis to explore their influence on the bearing and deformation characteristics of the engineering piles in the foundation pit during the further downward excavation beneath the existing building.