Numerical assessment on the consolidation characteristics of clays from strain holding, self-boring pressuremeter test

Abstract

The strain holding test (SHT), part of the self-boring pressuremeter test (SBPT), has been effectively utilized to determine the horizontal coefficient of consolidation (c(h)). However, the commonly used procedure proposed by Clarke et al. [Proc. 7th Eur. Comp. Soil Mech., Brighton 2 (1979) 207.] can lead to an erroneous estimation of c(h), because of its simplified assumptions. This paper deals with numerical analyses based on realistic test conditions of the generally accepted testing procedure, and using the most commonly used type of pressuremeter. The effects of the pressuremeter geometry, the partial drainage during cavity expansion, and the cavity strain level for the holding test are investigated with the radial distribution of the initial excess pore pressure and its dissipation rate. Based on the results of the numerical analyses, the curve of the time factor for the 50% degree of consolidation (T-50) needed to estimate c(h) is proposed with a modification method for soil permeability. Comparisons are made,between c(h) values estimated from the SHT of the SBPT and those obtained from other in situ and laboratory tests performed at two sites in Korea. These results confirm the improved capability of the T-50 values proposed herein. (C) 2002 Elsevier Science Ltd. All rights reserved.