Force Analysis Of Prefabricated Pile And ABAQUS Numerical Simulation On Pile-soil Interface

Because jacked piles exists many advantages has been widely popularized and applied in many areas especially buried soft soil.However,the rapid development of technology often makes its application ahead of theory and practice research,which has brought a lot of bad effects on engineering so that a number of researchers have carried out relevant experimental studies,including indoor,field and simulation.At present,the studies about the pile-soil interface gradually becomes focus,but the relationship between the interface normal stress and the shaft axial force has not been systematically revealed.In this paper based on the results of indoor model test,ABAQUS,the finite element numerical simulation software,are used to explore and analyze the interface normal stress and the axial stress of pile.The influence of the single variable on the interfacial resistance,adhesion and friction coefficient at different stages during the shear of pile-soil interface under different working conditions is revealed,and the influence of the normal stress on the interface resistance.The results of laboratory test were validated by numerical simulation.The specific work and research results of this paper are as follows:(1)In the pile-soil interface shear test,the elastic limit friction is less affected by the roughness and shear rate,which is restricted by the effective normal stress,and is largely affected by the water content,which would weaken the interfacial friction.The optimal water content is about 25%.The positive linear correlation of the elastic limit friction and the interfacial effective normal stress are strong respectively at the same roughness,water content and shear rate.(2)The interfacial limit friction increases gradually and tends to be stable with the increase of the roughness,existing about 4 mm optimal roughness,under the experimental conditions.The moisture content has a great influence on the interfacial limit friction,and existing about 25% optimal moisture content.The interfacial limit friction first increases and then decreases with the increase of the shear rate,existing about 0.6 mm/min optimal shear rate.The positive linear correlation between the ultimate friction resistance and the effective stress on the interface is strong at the same roughness,water content and shear rate.(3)The sliding friction increases with the increase of the roughness and tends to be stable,existing about 4 mm optimal roughness.The effect of water content on the sliding friction is controlled by the normal stress,existing about 25% optimal moisture content.The sliding friction is less affected by the shear rate.The positive linear correlation of the sliding friction and the interfacial effective stress at the same roughness and water content is strong.(4)The friction coefficient of sliding friction is largely affected by roughness,existing about 4 mm optimal roughness.The roughness has an enhanced effect on the adhesion,which is small and limited.The water content has small effect on the friction coefficient,existing about 25% optimal moisture content.The adhesion increases with increasing moisture content,and will be weakened.The friction coefficient and the adhesion are affected by the shear rate,existing about 0.6 mm/min optimal shear rate.(5)In the indoor model pile test,the load is mainly born by the pile end during the penetration process.The total pile side friction is small,the initial growth is faster and the latter stage is slower.The axial force of the pile is relatively large,which increases with the depth of penetration,and the growth rate along the depth decreases.The critical depth of the pile side friction resistance is 4D or 0.343 L below the top of the model foundation.(6)When the penetration depth is less than 1D or 3D ~ 6D,the pile-side friction resistance at same penetration depth is strengthened,and the resistance with larger depth is strengthened more obviously.When the penetrating depth is 1D ~ 3D,the pile-side friction resistance of the same penetration depth is degraded.(7)The neutral point is about 0.357 L or 4D below the pile top.When the penetration depth of the pile is less than 3D ~ 4D,the residual positive friction is small.When the penetration depth of the pile exceeds 9D,the residual negative friction resistance of the pile side gradually converts to the residual positive friction resistance.When the penetrating depth is about 2.5D ~ 3.5D,the residual positive friction resistance of the same penetration depth is 1.97 times higher than that of the front cross section.When the penetrating depth is about 5D~7D,the residual negative friction resistance of the same penetration depth is 1.97 times lower than that of the front cross section.(8)The simulation results and the measured values show similar change law along the depth.The numerical difference between the two is small and the fitting result is also within the allowable error range.This proves indirectly to the feasibility of the application of the silicon piezoresistive pressure sensor used in the laboratory test in other geotechnical engineering applications and to demonstrate that the test results obtained from the indoor model tests are feasible.