CPT testing in Dublin Boulder Clay

Abstract

The primary superficial deposit within the greater Dublin region (Ireland) is a stiff lodgement till, known colloquially as Dublin Bolder Clay (DBC). This material`s high stone content and strength often make good-quality undisturbed sampling extremely difficult. CPT testing is still rare, with present site investigation practice in DBC for routine design generally involving standard penetration testing. This paper brings together the body of knowledge and experience gained in the use of piezocone (CPTu) technology in characterising DBC deposits for 3 different sites, including the relationship be-tween CPT cone tip resistance, qc, and peak undisturbed undrained strength. Although the CPT data were 'spiky` on account of the high stone content and possible frequent dense sand/gravel lenses present, significant features were identifiable including coarse seams present and the transition boundary between the brown DBC and underlying stiffer black DBC.