The Mechanism And The Pore Pressure Behavior Of The Sleeve Of Large Diameter Benoto Pile Driving By High Frequency Vibratory Driving

Since the improvement of the settling tube cast-in-place piles to the soil squeezing,it has being widely used in most engineering.Then the Benote piles improved the construction technologies,it is more safe and convenient.And the high frequency hydraulic vibratory piles improved the technologies further,with the advantage of the flexible operation,low vibration sense,low noise and high mobility,it has drawn more and more attention.In order to research the effects of the high frequency hydraulic vibratory driving on the surrounding soils and the features of the soil plug in the tube,following works have been done in this paper to obtain the corresponding results.1?The combination of the Arbitrary Lagrangian-Eulerian(ALE)method and the numerical simulation of large deformations suggested by Henke&Grabe is used to simulate.The axisymmetric model is established to analyse the high frequency hydraulic vibratory driving.The effects of the penetration on the surrounding soils under undrained condition and the features of the soil plug in the tube are investigated.The constitutive model of Mohr-Coulomb is uesd to imitate the clay,the undrained indexs are applied in this analysis.The Finite-element and Infinite-element Coupling model is applied to eliminate the effects of the boundary reflection of vibration wave on the results.2?The numerical models of different installation methods are established to study the the features of the soil plug in the tube during tube driving.The different installation methods include jacking,impact driving and the high frequency hydraulic vibratory driving.Then the impact analyses of the high frequency vibration parameters have been made to investigate the stress state of soil in the tube during the high frequency hydraulic vibratory driving,so the analyses of the features of the soil plug in the tube can be got.The high frequency vibration parameters include the penetration rate,the static force(the high frequency vibration pile driver counterweight)and the exciting force.3?The further researches are performed to study the soil arching effects in the tube with the different defonnation modulus of the soil,the different friction coefficients between the tube and the soil and the different cohesion of the soil.4?With the analytic solution the excess pore pressures formed under the high frequency hydraulic vibratory driving can be calculated based on the numerical simulation.And by means of the three-dimensional drawing software Surfer11,the contour map of the excess pore pressures on the analysis domain can be ploted.And the transient consolidation is established by the ABAQUS/Standard to analyze the excess pore pressures dissioation after the high frequency hydraulic vibratory driving.5?For purpose of confirming the reliability of the numerical simulation method,the simulation of the penetration of a steel pipe pile has been established.And the numerical calculation results are compared with the test results,the theoretical calculation results of the strain path method and the theoretical calculation results of the cavity expansion method.Through the above analyses show that the high frequency vibration method can reduce the friction coefficients between the tube and the soil,so the influence of the soil arching effects can be receded,and the soil plug may not be formed.Then the tube can be driven into deeper depth more efficient,and the tube penetrates in the partial plugged mode.Moreover,during the high frequency hydraulic vibratory driving the excess pore pressures distribute near the pipe tip in bubble shape.When the driving force in a smaller degree,the caly with the high vibratory compaction is equal to the overconsolidated clay,so the clay takes on a dilatancy trend and shows a increasing of void ratio.After the adjustment of the internal stresses,the effective stresses increase with the decline of the pore pressures(may even go negetive).