Experimental Studies And Numerical Analyses Of The Pile-Soil Interface Property And Its Effects On The Vertical Bearing Behavior Of Bored Piles

Mud is used for protecting the soil wall in the construction of bored piles, mudis generally higher than the groundwater, clay particles in the mud are attracted to thesoil wall and permeated to the soil under the water pressure, which mud is formed onthe soil wall. Mud with surface lubrication, high moisture content, low compressionand low intensity, reduce frictional resistance between pile-soil, which affecting thevertical bearing behavior of pile foundation. This article mainly via the way ofexperimental and numerical analysis to studies how effect on vertical bearing capacityof pile foundation by mud.This article by the large stress type direct shear apparatus, which is developed byourselves, research on what the effect of mechanical properties of interface betweensoil and concrete surface, which existing mud, convex surface and concave surface.The test results shows that: mud of exists reduce the strength of interface between soiland pile, and the degree of diminution is small with the change of normal stress;convex of exists improve the strength of interface between soil and pile, and thequantity of increase will reduce with the increase of normal stress; concave of existsenhance the strength of interface between soil and pile, but a small degree, and theincrement is not obvious with the change of normal stress.This article also explores how the mud effect on vertical bearing capacity ofbored pile by the field model tests. The test results indicates that: the effect of verticalbearing capacity of bored pile with mud may ignore in low load, but the mud increasethe settlement of the pile in high load, what is more, the incremental settlement isincreasing with the augment of the load; The existence of mud will reduce the verticalbearing capacity of single pile, the degree of reduction is about15%.This article established bored piles model of three dimensional large by finiteelement software ABAQUS, and analyzed the differences of bearing behaviorbetween the pile with mud and without, meanwhile, it also researched the influencelaw of the vertical bearing capacity of pile foundation by the thickNess，elasticity，strength of mud and interfacial strength between the mud and concrete. The resultsindicate that mud reduces the friction resistance of interface between soil and pile,thus it reduces the vertical bearing capacity of single pile; mud with the increase of thickness or the decrease of elastic modulus, which is mainly reduce the normal stressof interface between soil and pile, thus reduce the vertical bearing capacity of the pilesfoundation; What is more， the single pile without mud rarely appears plasticdeformation in the end of the pile, but the single pile with mud appears plasticdeformation in the end; The limit friction resistance from side of the pile is the lesserof the interface strength between pile and mud and the strength of the mud.