Pseudo-N-value from the S-wave Velocity - A Proposal for Communicating with the Civil Engineers

Abstract

The N-value by standard penetration test (SPT) is a “traditional” indicator of ground competence. Its physical background is somewhat doubtful, it is well established in the civil engineering. The recent development of multichannel analysis of surface waves (MASW) outputs S-wave velocity distribution. It is a physical property to describe competence. Relationship between t the SPT N-value and the S-wave velocity from physical measurements was examined. Using empirical relationships and the standard soil description for the SPT N-values, a simple conversion formula is proposed . The N-values thus calculated from the S-wave velocity is subject to a possible range of error. The term “N-value” implies the in-situ method of penetration test. To avoid confusion, the term “pseudo-N-value” is also proposed to denote the N-value calculated from S-wave velocity. The pseudo-N-value is merely a parameter for communication with the engineers who are familiar with the SPT N-values, and the S-wave velocity is considered a better parameter of competence of the ground. The pseudo-N-value may be displayed in terms of soil classification, and it is more easily understood by the civil engineers.