1. SPTs in chalk: a rethink
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Published:1989
R.N. Mortimore, D. Jones, 1989. "1. SPTs in chalk: a rethink", Penetration testing in the UK: Proceedings of the geotechnology conference organized by the Institution of Civil Engineers and held in Birmingham on 6–8 July 1988, Institution of Civil Engineers
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The examination of SPT ‘N’ values in the White Chalk Formation of southern England reveals six distinct profiles which seem to be primarily related to geomorphology but which are also influenced by the sedimentation history of the Chalk.
(i) A Mundford profile (wakeling, 1970)
(ii) A dry valley profile typified by Saltdean, Brighton
(iii) A steep slope profile
(iv) A hill top profile with and without pipes (e.g. Rushy Hill & Falmer)
(v) A profile beneath pipes such as Falmer
(vi) A profile in highly weathered chalk below water table (Burland, Kee & Burford, 1975).
‘N’ profiles such as Portobello, Telscombe, Brighton, start below the weathered horizons of a dry valley and with the other localities illustrates the difficulty of applying the Mundford Grades to every situation in chalk. It is suggested that strength, fracture spacing and fracture tightness should be recorded separately for geotechnical analyses. The relationship of E average, obtained from plate bearing tests, to SPT ‘N’ values is reinterpreted.
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