Theoretical And Experimental Research On Low Order Resonance Frequency Of Piles

Low order resonance frequency of one-dimensional (1D) and spaceaxisymmetric (3D) soil-pile system models, with a vertical transient impact forceapplied to the pile top, is studied theoretically. The definite solution problem of1Dsoil-piles system model, in which the soil around the pile(SA) and at the bottom(SB)are uniform, isotropic and linear elastic, is deduced by Laplace transform andresidue theorem. Analytical solution expressions of particle vibration velocity ontop of the pile, pile-soil system transfer function and low order resonancefrequency are obtained in frequency domain, and there is a good agreementbetween measured velocity curves obtained by low strain dynamic testing onengineering piles and calculated curves ploted by a MATLAB program. Thecharacteristics of time-domain velocity curve V(t), velocity amplitude spectrum|V(f)|and velocity or mechanical admittance|H(f)|are analyzed quantitatively whenparameters of the pile, SA and SB are changed. Then, after both numerical solution,calculated by finite difference method (FDM),of the1D pile-soil model and that ofthe3D soil-pile system model prove to be correct, The curves of V(t),|V(f)|and|H(f)|both in1D and3D models are drawn and analyzed with rock-socketed depthH2and pile bottom sediment thickness H3of rock-socketed pile varying. Finally, itshows that both the1D and3D numerical results share some common rules.