Use of an Instrumented Flat Dilatometer in Soft Varved Clay

This paper describes the use of an instrumented dilatometer (IDMT) equipped with sensors designed to record the continuous displacement of the membrane, the total pressure, and the pore water pressure. The IDMT was tested in the Connecticut Valley Varved Clay at the University of Massachusetts—Amherst National Geotechnical Experimentation Site. The results, presented in terms of profiles of pore pressure during insertion, corrected pressures, dilatometer indices, and shear modulus are compared to results from the standard dilatometer, the self-boring pressuremeter, the seismic cone, and the seismic dilatometer. The results from the tests suggest that the IDMT can be used to provide accurate and cost-effective values of unload–reload modulus and, the complete pressure–displacement curve could potentially be used to develop improved correlations for strength and initial in situ stresses. In addition, the continuous pressure–displacement response and the pore pressure measurements provided insight into the mechanics of the dilatometer expansion in partially drained conditions.