Theoretical study on torsional wave applied in low strain dynamic testing of piles

A solution to the torsional response of a multi defective pile in layered soil is presented,when subjected to an impact torque at pile top.Soil pile interaction is considered in this approach. The partial differential equations of torsional vibration of pile have been solved using Laplace transform and transfer matrix,which satisfy the initial conditions and boundary conditions.The transfer function of soil pile system is derived.The frequency response function and frequency domain expression of torsional vibration velocity at a point on pile top are obtained.The time history of the velocity is calculated using inverse fast Fourier transform.The solution is used to study torsional wave characteristics of the pile.The conclusion will be of guide significance on low strain dynamic testing of pile with torsional wave.