Time-effect Study On Bearing Characteristics Of Static Pressure Pile In Saturated Silty Soil Foundation

In pile foundation construction,static pile sinking becomes one of the most popular construction methods in urban construction because of its advantages and characteristics.The research on the time effect of the bearing characteristics of static pile has always been a concern in geotechnical engineering.It is of great significance to study the time effect of the bearing characteristics of static pile so that the advantages and characteristics of static pile can be fully played in the application value of engineering.In this paper,static pile driving tests are carried out in saturated silt soil foundation.Laboratory simulation tests are carried out on the bearing characteristics of static pile and the timeliness of residual stress at pile tip under different overconsolidation ratios and different roughness of pile surface.The main conclusions are as follows:In this paper,non-Darcy seepage characteristics are introduced to describe the dissipation of excess pore water pressure in soil around piles.The traditional axial-symmetric radial consolidation equation of soil around piles is modified and solved by finite difference method.The influence of Hansbo seepage parameters on dissipation of excess pore water pressure and lateral consolidation rate of soil around piles is discussed.The results show that the dissipation of excess pore water pressure around piles will be overestimated if the non-Darcy property is ignored.For different saturation powder soil coefficient of static earth pressure and the undrained shear strength,this paper,by using GDS stress path triaxial apparatus for saturated silt K₀consolidation and super normal consolidation test and undrained shear test,the saturated silt under different stress path coefficient of earth pressure at rest and undrained shear strength.In undrained shear tests under different stress paths,the undrained shear strength of saturated silt increases with vertical consolidation pressure.Under the same overburden pressure,the overconsolidation ratio of saturated silt increases.In order to study the bearing characteristics of static pressed pile and the timeliness of pile tip residual stress,this paper uses independently developed pile foundation model test device to conduct laboratory model test,and consolidates saturated silt soil foundation with different stress paths.Static piles with different roughness of pile surface are sunk into saturated silt soil foundation with different overconsolidation ratios.After static piling,static load tests are carried out on static piles on 2d,9d and 19d respectively.The rest periods after static piling are 2d,7d and 10d respectively.The timeliness of load bearing characteristics and the change of pile tip residual stress with resting time are discussed and analyzed.According to the test results,the vertical ultimate bearing capacity of the pile increases with the increase of the overconsolidation ratio of saturated silt foundation when the pile surface roughness is the same.When the overconsolidation ratio of saturated silt soil foundation is the same,the vertical ultimate bearing capacity of static pressed pile increases with the increase of pile surface roughness.The change of pile tip residual stress with resting time is complicated,and the pile tip residual stress is closely related to the ultimate friction resistance of pile side.