Short- and long-term sharp cone tests in clay

Abstract

Listen

Translate article

A recently developed in situ testing method, called the sharp cone test, which is in fact a continuous and automated version of the pressuremeter test, consists of pushing a low-angle truncated cone into a smaller diameter prebored or self-bored pilot hole. As the cone descends, it causes a continuous enlargement of the pilot hole, which, with proper instrumentation, can be translated into a relationship between radial pressure and radial (or shear) strain, similar to the expansion curve of a pressuremeter test. The present paper describes the use in the field of two new versions of this instrument: the first one with 2° taper, having on its lateral surface four total pressure transducers and a pore pressure transducer; and the second one with two successive taper angles of 1° and 2°, having five total pressure transducers installed at various distances from the tip. The latter probe was found to be capable of continuously furnishing five points on a pressure-expansion curve, which can be translated into a stress–strain relationship by using conventional pressuremeter data-processing procedures. The first probe, in turn, was used for simultaneously observing the decrease with time of both total lateral pressure and pore pressure during strain-holding periods of the test. In 2002, the two newly designed instruments were tested in a thick layer of saturated clay at a site near Montréal. A comparison of the results with those obtained at the same site by some other types of tests is very encouraging.Key words: field tests, clay, sharp cone, pressuremeter, short term, long term.