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Development of an Instrumented Borehole Drilling System for Ground Investigation
Assistant Professor, Civil Engineering Department, and Development Director, Soletanche Bachy |
Abstract
The drilling of holes for grouting tubes creates the potential for obtaining supplementary ground information, which can be valuable to the succeeding tunnel construction. Based on the offshore exploration technique, an onshore instrumented drilling system that uses a set of pressure transducers placed at various locations of the hydraulic circuits of the machine has been developed and tested on site for ground investigation in order to examine its power to discriminate between ground strata. The method can theoretically be used in nearly every soil type for qualitative interpretation of soil formation changes while grout holes are being drilled. Because of its relatively small sampling interval - at every 5 mm - it can offer to assess local variability of soil formation, which can sometimes be missed by conventional site assessment methods.
In this study, the performance of this system was validated by testing at Kennington Park and Jubilee Line Extension site, in London. The result was then compared with the soil formation obtained from cores samples. Certain components of the drilling system and drilling method have been studied and standardized so that meaningful and globally applicable results can be obtained in the future. The effects of inconsistent drilling system and methods on the quality of data have also been quantified by means of cross-correlation analysis for groups of standardized and non-standardized tests.
Keywords: instrumented drilling, borehole, ground investigation, site characterization.
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