Instrumented Borehole Drilling for Subsurface Investigation

The successful application of instrumented borehole drilling techniques in offshore exploration has encouraged its further use on-shore as a ground investigation tool. The drilling of holes for grouting tubes creates the potential for obtaining supplementary ground information, which may be valuable to the succeeding tunnel construction. The instrumented drilling system was therefore investigated to determine its power to discriminate between ground strata. The configuration of the drilling system in terms of plant, equipment, and testing procedures was standardized and applied at a site in Kennington Park in London. The general characteristics of the measured drilling parameters are given and qualitative and quantitative methods of interpreting the drilling parameters are demonstrated. The possible soil–machine interactions that are responsible for the measured drilling characteristics are examined. A new method of data interpretation is proposed for identifying soil formation changes. Previously published correlations and analyses of drilling were examined and tested by comparing the trend-lines of drilling data in London clay against known undrained strength data. The degree of correlation was found to be limited.