Study On The Influence Of Embankment Filling On Adjacent Pile Foundation In Deep Soft Soil Area

The construction of new highway and railway embankments can have a significant impact on the performance of adjacent existing pile foundations,especially in coastal areas where high embankments and large areas of deep and soft soil are common.The filling of embankments may cause large lateral displacement and bending moments of nearby existing pile foundations,even leading to serious disasters such as foundation deflection and unstable failure.This paper relies on a new high-speed highway project in the coastal areas of Guangdong Province.The ramp roadbed section with deep and soft soil layers was selected to carry out a field load test on adjacent pile foundations.A three-dimensional numerical model analysis was conducted to study the stress and deformation of pile foundations under the action of embankment filling,the displacement rules of foundation soils,pile-soil interaction and other contents in the area with deep and soft soil.Firstly,a prototype test was conducted onsite where the height of the embankment was 4 meters,and it was filled five times equally in height to explore the changing rules of the pile top displacement,pile body inclination,pile side soil pressure,pore water pressure and foundation soil displacement under each level of embankment load.The relationship between the pile body displacement during the loading period of each filling level and the pile body displacement during the static period was analyzed,as well as the change in the shear sliding surface.The stress-deformation characteristics of adjacent pile foundations under the action of embankment loads,the pile-soil load transmission mechanism,and the development law of pore water pressure in soft soils were studied in depth,revealing the mechanism of stress and deformation of adjacent pile foundations under embankment filling.Secondly,using numerical calculation methods and FLAC^3D finite difference software,we established a numerical model to simulate the aforementioned field test.We elaborated on the selection process of pile-soil contact surface parameters and verified the rationality and accuracy of the numerical model using measured data.We also studied the pile body displacement,foundation soil displacement,excess pore water pressure（EPWP）,and foundation soil horizontal resistance.We delved into the inner forces and deformation characteristics of adjacent single piles under the action of embankment loads as well as the lateral displacement rules of different depths of soft soils.In addition,we calculated and analyzed the proportional coefficient m value of the horizontal bearing capacity of foundation soil at the test site.Finally,based on the aforementioned three-dimensional numerical analysis model of adjacent piles and embankment load test coupled with field test data,we carried out parameter analysis on four key factors:（1）bending stiffness of piles;（2）distance between embankment and piles;（3）height of embankment;（4）thickness of cushion layer.We studied their influence on stress and deformation characteristics of single piles in deep and soft soil foundations and proposed a treatment method using crushed stone piles to reinforce deep and soft soil foundations.The research results have good theoretical and engineering application values providing important references for design and construction of similar projects involving construction of new embankments adjacent to pile foundations.