Abstract：Considering soil-pile interaction，the dynamic torsional response of a pile in time domain is investigated theoretically. The pile is assumed vertical and with elastic bottom boundaries and the soil is considered as visco-elastic layer with hysteretic type damping. The soil layer alone is solved first and its vibration torsional angle solution with undecided constants is used in the analysis of pile response. Then by solving dynamic equilibrium equation of pile，the pile response to a harmonic load is obtained in a closed form and a semi-analytical solution of the velocity response of pile subjected to a semi-sine wave exciting torsional couple is also given. In comparison with other theories，the correctness and applicability of the theoretical solutions presented herein are verified. Based on the solution，a parametric study is conducted to determine the main features of dynamic response of pile in time domain，and the special influence of hysteretic type damping of soil layer，slenderness ratio，soil modulus are also discussed here.
