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Relative densities and void ratios derived from CPT data using in situ field calibration

: Biryaltseva, T.; Mörz, T.; Brandt, S.; Kreiter, S.; Gerdes, U.; Ossig, B.

Fulltext urn:nbn:de:0011-n-4259748 (726 KByte PDF)
MD5 Fingerprint: 7dd6e2ebc1ea3201189bec4ea9d0bbc3
Created on: 3.5.2017

Lehane, B.M. ; Australian Geomechanics Society -AGS-, Sydney:
5th International Conference on Geotechnical and Geophysical Site Characterisation, ISC 2016. Proceedings. Vol.1 : Gold Coast, Queensland, September 5-9, 2016
Sydney: AGS, 2016
ISBN: 978-0-9946261-1-0
International Conference on Geotechnical and Geophysical Site Characterisation (ISC) <5, 2016, Gold Coast>
Conference Paper, Electronic Publication
Fraunhofer IWES ()

This study shows the results of an attempt to develop a transfer function of cone resistance measured in medium over-consolidated sands (< 2 MPa) toward relative soil density and absolute porosity solely based on in-situ testing. In a sand pit, a water saturated, Late Pleistocene fluvial section of 15 m thick-ness with homogeneous grain size distribution and comparable emax and emin values, but highly variable cone resistance was selected for testing. Two ~25 m deep sampling holes, six CPTs and two approximately 40 m deep neighboring flush drilled holes for downhole logging with a horizontal distance of 2.5 m to the CPTs were used in this study. Relevant downhole logging parameters are wet bulk density derived from active gamma logs and porosities derived from neutron-neutron logs. The results show a straightforward stratigraphic picture with clear soil package boundaries. However, within the sand formation of interest fluvial foresets bars, top sets and incised channels with local unconformities lead to changes of stratigraphic height over short horizontal distances challenging in turn the correlation of logging and CPT data. Despite these difficulties, the project resulted in a new transfer function for glacially overconsolidated sands not only linking tip values to relative density but also directly to porosity, making sampling at least for stratigraphic equivalent sands no longer a requirement.