Pseudo-N-value from S-wave velocity: A consideration for geotechnical application

Abstract

Summary The SPT N-value is commonly used by engineers as an indicator of hardness of the ground. The load-bearing capacity derived from the N-value is used as a basis of subsequent engineering design. Among geophysicists, hardness of the ground is expressed by seismic velocity. The multichannel analysis of surface waves (MASW) delivers S-wave velocity structure with a high data density which is hard to achieve by the SPT surveys. Many authors attempted to relate these two parameters from the empirical correlation. Any proposed equations, albeit with great precisions, inevitably contain some error. Accepting the error range, the pseudo-N-value was proposed in 2011 to estimate N-value from S-wave velocity with simple conversion parameters. The pseudo-N-value does not reference to a particular site and it can be used where actual SPT data is not available. It is displayed as a seismic section in terms of N-value. This conversion provides the engineers with trend of distribution of ground hardness with high data density. This presentation includes an example of practical use of pseudo-N-value in a geotechnical site.