中文摘要：

本文采用Novak薄层法推导粘弹性地基的扭转动力阻抗，并将其用于考虑桩土相互作用的单桩扭转动力阻抗，又通过传递矩阵法将此公式推广到求取层状地基单桩扭转动力阻抗。而且本文以工程中常用的端承桩为例，推导了层状地基中端承桩扭转动力阻抗的简化计算公式。根据此公式，分析了频率、上覆软土层厚度、上覆软土层刚度等因素对单桩扭转动力阻抗的影响，分析结果表明，随着振动频率提高，层状地基中端承单桩的扭转动力阻抗的实部有缓慢下降的趋势，而虚部则增大；随着上覆土层厚度的增加，层状地基中端承单桩的扭转动力阻抗的实部和虚部均减小；随着上覆土层刚度的减小，层状地基中端承单桩的扭转动力阻抗的实部减小，虚部在低频段减小，而在较高频率段则增大。

英文摘要：

Novak layer method which was appliesd to compute the dynamic impedance of torsional vibration for layered soils is introduced to analyze the torsional dynamic pile-soil interaction. The computing formula for torsional dynamic im.pedance of single pile in layered soils is got by transfer matrix. Furthermore, according to the end-bearing pile which is usually applied to engineering, the simplified formula for torsional dynamic impedance of endbearing pile in layered soils is obtained. On the basis of this formula, the effect of frequency, and thickness and stiffness of topsoil on the torsional dynamic impedance of single-pile is analyzed. The results show that the real and imaginary parts of the torsional dynamic impedance of end-bearing pile in layered soils decrease along with the augment of the thickness of topsoil ; the real part of the torsional dynamic impedance for end-bearing pile in layered soils decreases and the imaginary part of the torsional dynamic impedance for end-bearing pile in layered soils heightens along with the increase of frequency. When the stiffness of topsoil is diminished, the real part of the torsional dynamic impedance of end-bearing pile in layered soils reduces.