Improved calculation for lateral dynamic impedance of pile groups in layered soil

Based on a dynamic Winkler model, a simplified calculation method of both active and passive piles in the case of multi-layered soils is presented. An advanced method is deduced to compute the lateral dynamic impedance of both single pile and pile groups in multi-layered soils, which takes pile shaft shear deformation and moment of inertia into account. Compared with the already results of experiment and computations, the presented results are more close to the tests. The text result is consistent with a correlative thesis in low frequency, but both difference increases when pile shaft shear modulus decreases. Pile shaft shear modulus and moment of inertia are the reasons to cause the differences. The former plays a greater effect even in low frequency. The latter has a little effect, but an evidence differences appear during the pile impedance in peak value and the frequency is high. Thus pile shaft moment of inertia should be taken into account in high frequency.