Ring Shear Test Of Saturated Silty Soil-mud-concrete Interface And Research On The Parameters Of The Boundary Surface Model

Slurry wall protection commonly used hole-forming techniques for bored piles.When the pile passes through the deep silty soil,under the vertical load,the bearing capacity of pile foundation and the relative displacement between pile and soil are determined by the shear behavior of saturated silt,mud and pile.Based on the interfacial ring shear test,this paper mainly studies the interfacial shear behavior of saturated silt-concrete interface due to the existence of mud crust and the difference of concrete surface roughness,and discusses the influence of mud,contact surface roughness,normal stress and other factors on the interfacial shear behavior.Finally,the parameters of the interface boundary surface model were fitted based on the test results,and the constitutive integral algorithm of the soil-structure interface boundary surface model was established.The interaction between soil and structure surface was analyzed by using the secondary development subroutine Uinter provided by ABAQUS finite element software.The following conclusions were obtained:(1)Under constant normal stress,the interfacial shear tests of concrete with different roughness and saturated silt were carried out;the experimental results showed that the shear strength of the interface increased with the increase of roughness when the roughness of the contact surface is smaller than the critical roughness.When the roughness of the contact surface is larger than the critical roughness,the shear strength of the interface is close to the internal shear strength of the soil.Before reaching the critical roughness,the interface friction Angle and interface cohesion are proportional to the logarithm of the roughness of the contact surfacelog(7)R(8).By comparing the interfacial shear test with the internal shear test,it was found that the shear failure gradually extends from the interface to the interior of the soil.(2)Under constant normal stress,the interfacial shear tests of saturated silt-mudconcrete with different roughness are completed.The test results showed that after adding mud,the stress-strain curve exhibited a softening phenomenon.The interfacial shear strength decreased greatly while the value of critical roughness decreased obviously and the interface friction Angle decreased significantly.(3)When studying the change of soil volume caused by shear,it was found that there was no obvious dilatancy in the two kinds of interface shear tests.In the shear process,contraction was positively correlated with the normal pressure and negatively correlated with the roughness of the contact surface.After adding mud,contraction decreased.(4)Comparing the calculation results of the interface boundary surface model with the experimental results,it is found that: although the interface boundary surface model is often used to describe the interfacial shear behavior of coarse-grained soils such as sand,it is also a better choice to describe the interfacial shear behavior of silty soils.(5)ABAQUS finite element software was used to analyze the interaction between soil and structure.It was found that the interface boundary surface model had a poor coincidence degree for soil body change,but high coincidence degree for interface shear stress.The coarser the contact surface,the smaller the pile settlement,the larger the axial force,the larger the pile side friction resistance,the larger the volume change caused by shear.When the roughness of pile side is the same,with the increase of pile depth,the settlement of pile body decreases,the axial force decreases,and the friction resistance of pile side increases first,then decreases and finally reaches zero.