Causes of sampling disturbance and design of a new sampler for sensitive soils

Abstract

The behaviour of a clay element during the sampling operation is first analysed in the light of the limit state theory. The stress variation and the resulting distortion of the clay element during sampling is equivalent to a destructuration of the clay, and its mechanical properties are greatly affected. The causes of sampling disturbance are analysed and the principles which should govern the design of a good quality sampler are reviewed in the light of previous studies. It is shown how the reshaping of the sampling tubes can improve the sample quality. The new 200 mm sampler designed at Université Laval uses the overcoring technique to eliminate suction and to insure the recovery of large samples without a piston. The quality of these large samples has been proven to be equivalent to block samples. The advantages and limitations of the Laval sampler are discussed.

An attempt to monitor pore pressure changes in a block sample during and after sampling

“…Hvorslev, 1949;Clayton, 1986) • sampler type (e.g. Berre et al, 1969;Lefebvre & Poulin, 1979;La Rochelle et al, 1981;Baligh, 1985, Amundsen et al, 2015a • sealing, transportation, thermal variations, storage method, trimming and handling during preparation for testing (e.g. Bozozuk, 1971;Arman & McManis, 1976;La Rochelle et al, 1976, 1986Atkinson et al, 1992) • stress relief during and after sampling (e.g.…”

Effects of Sampling Tube Geometry on Soft Clayey Sample Quality Evaluated by Nondestructive Methods

“…Lefebvre and Poulin (1979) designed a new sampling method called the Sherbrooke sampler. At the same time, La Rochelle et al (1981) developed a new large diameter sampler called the Laval sampler. They concluded that both the Sherbrooke and Laval sampler yield better sample quality than conventional tube samplers.…”

Undisturbed Sampling and Laboratory Shearing Tests on a Sand with Various Fines Contents

“…The Laval sampler as schematically described in Fig. 5 was developed at Laval University (La Rochelle et al, 1981), originally for taking high quality samples in sensitive clay. The sampler is made of two main parts; a sampling tube and an overcoring tube.…”