Analysis And Shaking Table Tests Of Liquefaction Resistance Of Rigid Drainage Pile

The liquefaction due to earthquake would cause serious damage to the constructions and structures,such as collapsed,subsidence,capsized and buoyancy of buried pipeline,the bridge collapsed,instability and failure of pile foundation,etc.Building collapse was often caused by the loss of bearing capacity of pile due to foundation liquefaction.In the field investigation,it was found that when the earthquake liquefaction occurred,because of the inertial forces,the rigid pile foundation was easily broken at the interface between the liquefiable soil and the unliquefiable soil.Thus,the pile foundation lost its bearing capacity and the superstructure collapsed.Flexible pile foundation(such as compacted sand pile,gravel pile,etc.),due to the existence of drainage channel in the pile body,when the soil liquefied,the excess pore pressure generated inside the soil can be discharged from the drainage channel.The excess pore pressure of the soil was reduced,and the pile body will not be seriously damaged.However,the bearing capacity of flexible pile was low,which often fails to meet the requirements of superstructure Composite the advantages and disadvantages of rigid pile and flexible pile,based on the method of innovation and practice of geotechnical engineering complement,a new kind of rigid drainage pile was proposed.Rigid drainage pile body for precast concrete,open a circular or square drainage grooves in precast concrete pile body,set the drainage material match the groove shape and size within the drainage groove(plastic drainage plate or blind ditch of drainage).When foundation suffered the earthquake shaking,the drainage channel can dissipate the excess pore pressure,prevent damage of pile foundation.In this study,a series of shaking table tests were carried out to investigate the anti-liquefaction properties of the rigid drainage pile for liquefiable foundation.The main research contents of this paper were:(1)Based on the shaking table test,the drainage performance of the rigid drainage piles under different conditions(different number of drainage channels and different angles)was studied.Drainage performance is the most basic and main performance of the rigid drainage pile,and it is the key factor to the anti-liquefaction of the rigid drainage pile.In this paper,the discharge volume of flow is measured and analyzed by means of shaking table test(2)Based on the shaking table test,the anti-liquefaction properties of the rigid drainage pile to treatment of liquefied soils under the load of equivalent overburden embankment were studied.During the tests,the purpose of the upper department on the pile top was simulate the pile foundation embankment load,the excess pore pressure ratio,acceleration,lateral displacement of the pile top was measured and to estimate the effect of liquefaction resistance of rigid drainage pile.The peak of excess pore pressure ratio in the working condition of the drainage rigid pile was smaller,and the dissipation rate of the excess pore pressure was faster.The strength and stiffness of the soil were better maintained(3)Based on the shaking table test,the properties of liquefaction resistance between the rigid drainage pile-net composite foundation and the ordinary pile-net composite foundation were compared.In order to guarantee the consistency of test conditions,drainage pile-net composite foundation and the ordinary pile-net composite foundation were set on the same test model.The settlement of the upper embankment can be effectively reduced by the rigid drainage pile-net composite foundation,which shows excellent effect on the reinforcement treatment to the liquefiable foundation under embankment load.(4)The anti-liquefaction effect of the rigid drainage pile for liquefiable soils was studied First,the numerical analysis model of the shaking table test was established,and through comparison and verification with the results of the shaking table test,the reasonable calculation parameters were established,and the three-dimensional numerical analysis model of the liquefied embankment foundation was established.Through the numerical analysis model,the influence factors(relative density and drainage path layout)to the effect of anti-liquefaction of rigid drainage pile were investigated.The effective influence range and the distribution law of excess pore pressure around the pile were expounded.The results indicated that the effective range of excess pore pressure was one times diameter of the pile.The further from the drainage channel,the greater the excess pore pressure was.The location of the drainage channel had a great influence on the reinforcement effect.