Comparative Study On Numerical Simulation And Test Of Lateral Dynamic Response Of Symmetricald Double Inclined Piles

Pile foundation is the most common form of deep foundation in civil engineering.However,structures in cross-sea bridges,port piers,and oil and gas transmission projects are often damaged by collision force of ship,tides and earthquakes and so on,the inclined pile foundations are used to resist lateral load.Therefore,it is very important to study on seismic performance of inclined pile in saturated sand in development of earthquake engineering.Based on the electromagnetic shaking table test,a three-dimensional dynamic calculation model of symmetrical double straight piles and symmetrical double inclined piles in dry sand and saturated sandy soil is established by FLAC3 D finite difference software.The characteristics of lateral dynamic response of inclined piles in dry sand and saturated sandy soil are compared.The main research works are as follows:(1)In the shaking table test,a shear box with suitable size is selected and a test model is made according to the scale of equal proportions.A comparative analysis is made out for the lateral dynamic response of symmetrical double piles under different peak acceleration sine wave input.The results show that lateral dynamic response of symmetrical double piles in the dry sand is very nearly the same;under the circumstances of sand liquefaction,lateral dynamic response of symmetric double straight piles is significantly greater than the inclined piles.(2)FLAC3D calculation principle and completely nonlinear dynamic analysis method should have a systematic study.Based on shaking table test and Midas-GTS NX,FLAC3 D pre-processing software,a three-dimensional numerical model of symmetrical double piles is established.After grid meshing,FLAC3 D is successfully imported the initial stress and dynamic calculation,the initial pore water pressure of two monitoring points is monitored.The results show that the calculated values agree well with the theoretical values.(3)The numerical simulation results are compared with the experimental results,including the acceleration,the displacement time history and the peak value of the platform and the pile head cap.The study finds that both under the sine wave and earthquake wave input,when the occurrence of liquefaction of sandy soil,acceleration and peak displacement of double straight piles have an obvious amplification effect.Amplification effect of the double inclined piles is smaller than the symmetrical double straight piles,which is more significant especially when the sandy soil is liquefied.In dry sand,the simulation results are in good agreement with the experimental results;in saturated sa ndy soil,the simulation results are slightly larger than the experimental results.These results indicate that FLAC3 D can achieve better simulation of lateral dynamic response of inclined piles in dry sand and saturated sandy soil.(4)In the sine wave and earthquake wave excitation,the test monitors that time history of the pore water pressure has a rapid growth,and shows the phenomenon of sand blasting and water emitting.The FLAC3D’s numerical simulation reproduces well the change of pore water pressure,and the simulation results agree well with the experimental results.