Using Drilling Data to Derive Geotechnical Properties of Variably Cemented Materials

Abstract

Geotechnical site characterisation of variably cemented material is often challenging due to lack of data. Drilling data is routinely measured as a part of standard geotechnical site investigation and can provide an alternative method to derive continuous ground profiles with depth. This paper examines the use of drilling data for site characterisation purpose. Based on the drilling data obtained from an offshore windfarm project site, where variably cemented materials were found, it is shown that the borehole specific energy calculated using the drilling data reasonably captures the variation in material types with depth. Also, the results show that borehole specific energy can be correlated with the laboratory test data in a similar manner to cone penetration test. Based on the results obtained from different locations covering a range of material types and in-situ state conditions, generalised relationships between different geotechnical parameters and borehole specific energy are presented. An example of how the generalised relationships developed using borehole specific energy can be used to derive design profiles for a selected site is also shown. The data and interpretation approach presented in this paper provide a useful guide for how the drilling data can be used to assess the continuous ground profile for variably cemented sites where only limited or no in-situ test and intermittent sampling data are available.

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