Linear Trendlines to Assess Soil Classification from Cone Penetration Test Data
Publication: Journal of Geotechnical and Geoenvironmental Engineering
Volume 143, Issue 9
Abstract
The data format developed by Robertson and his coworkers to assess soil behavior type with cone penetration test data using a series of concentric circles can provide an unreliable assessment in overconsolidated soils. With increasing overconsolidation, the normalized net-tip stress-normalized friction ratio, , data for uniform-texture, but variably overconsolidated soils follow the shape of a hyperbola as shown by the generalized soil behavior type chart developed by Schneider and his coworkers. To improve soil classification from cone penetration test/piezocone penetration test (CPT/CPTu) data, a method is proposed that plots against , where is sleeve friction normalized by effective vertical stress. In space, CPT/CPTu data for a given soil yields a linear relationship with a slope designated . The linear relationships from many variably overconsolidated soils converge to a common origin that is offset from zero. When plotted in space, the linear relationships become hyperbolas, similar to the Schneider hyperbolas, but the position of the individual hyperbolas in space are defined by the offset origin location. The index provides a numerical value that can be linked to soil index and engineering properties. Using values computed for uniform-texture, variably overconsolidated soils, and empirical correlations between and soil index properties, a CPT/CPTu assessment chart is presented to improve soil classification and the generalized framework.
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Acknowledgments
The writers thank Bryan Kumm for his assistance with preparation of early drafts of figures for this paper. The writers thank Dr. Tsing Tsai for access to the digital CPTu data for the LA 1 site.
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©2017 American Society of Civil Engineers.
History
Received: Apr 20, 2016
Accepted: Feb 21, 2017
Published online: Jun 9, 2017
Published in print: Sep 1, 2017
Discussion open until: Nov 9, 2017
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