Storage duration effects on Norwegian low-plasticity sensitive clay samples

Abstract

he issue of soil sample disturbance is important when determining the representative geotechnical properties, especially for low-plasticity sensitive clay samples. These clays are often inhomogeneous, which makes such an issue even more challenging. Sample disturbance is related to the sampler type, sampling process, stress relief, transport, storage and specimen preparation prior to testing. When soil samples are tested, the effects of storage are often underestimated, or ignored, and limited information exists on how long a sample can be stored until its properties no longer represent the in-situ conditions.

This PhD work focuses on studying the effects of storage duration on Norwegian low-plasticity sensitive clay samples. The work is divided into a) a characterisation of the main test site, the Tiller site, b) investigation of the effects of storage on block samples, c) investigation and monitoring of stress relief in block samples, d) investigation of the effects of storage on 54 mm piston samples, and e) investigation and development of sealing methods for the storage of block samples.

The extensive experimental investigation on the effects of storage duration resulted in a general conclusion that immediate testing of a sample leads to a higher quality than that of stored samples. The effects of storage duration showed to be especially critical for the low-plasticity sensitive clays. To counteract this, a new method for storing block samples was developed, in which it is attempted to minimise the effects of storage by applying a storage pressure. The results from a pilot study showed that this is a promising avenue for further research.