ABSTRACT
Deriving undrained shear strength of clays from piezocone tests (CPTU) suits the use of a database approach, particularly because good correlations are expected on the basis of theoretical correspondence. Benefits of a database approach include a minimal environmental footprint and field schedule shortening, primarily because of reduced borehole sampling and laboratory testing focused on verification rather than development of comprehensive site-specific data sets. This paper expands on the classic expression su = qnet/Nkt where su is a reference undrained shear strength obtained by laboratory testing, qnet is the net cone resistance and Nkt is a cone bearing factor that is noted to decrease with increasing values of CPTU pore pressure ratio Bq. The database includes CPTU results and high-quality laboratory triaxial compression tests from 70 different clay deposits, of which 8 represent new case studies. The clays are allocated to 5 main categories: (a) soft-firm offshore; (b) soft-firm onshore; (c) soft sensitive; (d) stiff overconsolidated intact; and (e) stiff fissured clays. Organic clays and cemented clays are excluded.
