DV Morris and CP Abbiss. This paper was first published in GE’s November 1979 edition.
In order to predict immediate “elastic” deformation of soil, it is necsssary to know the appropriate elastic moduli. Traditionally these have been measured in-situ by various static tests. However these are often lengthy and expensive, and it is tempting to consider using seismic techniques instead, making allowance for different levels of strain.
Such a seismic investigation was carried out on a site of over-consolidated Gault clay that had been used for a number of pressuremeter tests, so that it was possible to compare the results directly.
A numerical method is presented for evaluating the general distribution of dynamic modulus with depth, from seismic results, by dividing the clay into discrete horizontal layers. The method was used to generate a vertical profile of shear modulus at this site. This was then converted into the equivalent values for the pressuremeter tests, using the results of independent resonant column work.
Very reasonable agreement was found although further experimentation is required to validate this technique.