A Practical Method For Estimating Impedance Functions Of Block Foundation Resting On Or Embedded In Layered Soil

It is important to estimate the influence of layered soil in soil-structure interaction analysis. Although a great number of investigations have been carried out on this subject, there are very few practical methods that do not require complex calculations. In this paper, a simple and practical method for estimating the impedance functions of a block foundation resting on or embedded in layered soil is proposed. In this method, waves propagating in the soil are traced using the conception of the cone model.On the basis of reviewing the work of John P. Wolf, the concept and the construction of cones to model a foundation on a homogeneous soil half-space or a soil layer on rigid or flexible rock are discussed. Then the translational and the rotational cones are addressed.The horizontal and rotational dynamic stiffness formulations proposed by Naohiro Nakamura for the block foundation resting on layered soil, which based on the method in which the wave propagation can be pursued over layer boundaries, are expanded by the author to calculate the vertical and torsional dynamic stiffness.The effect of embedment on impedance of block foundations is evaluated by several methods. The result shows that the effect of embedment not only affected by embedment but also significantly influenced by the frequency. The result could be referred in improving the methods of the dynamic response analysis of machine foundations.In this paper, several illustrative examples are discussed in order to explain the accuracy of the proposed method. In the finality, the problems requiring further studies are discussed.