A Concise Approach of Soil Models for Time-Domain Analysis

This paper proposes to represent the frequency dependence of soil parameters via a rational approximation in the frequency domain. Two types of causal soil models were considered, namely, Smith-Longmire and Alipio-Visacro (AV). Results indicated that for both soil models, the analyzed parameters maintain a fixed ratio between the poles and residues, and for the AV soil model, there is a unique set of poles, representing a “universal” set of relaxation frequencies. Thus, without resorting to an additional fitting process, one can find a suitable rational approximation of a frequency-dependent soil for an arbitrary conductivity, which is very useful for its inclusion in computational codes in time or frequency domains.