Arnfinn Emdal

Discussion of ‘Soil creep effects on ground lateral deformation and pore water pressure under embankments’

Settlement analysis of field cases is normally studied based on parameters interpreted from laboratory samples influenced by varying degrees of sample disturbance. Such disturbance is more pronounced in natural soft clays and could significantly affect the engineering properties of the soil, e.g. the over consolidation ratio (OCR) and compressibility index (Cc). Hence, it is vital to understand the role of sample quality in relation to soil characterisation for long-term settlement analyses. In this work, this is numerically illustrated by use of a simple creep model along with realistic parameter selection. This work takes its starting point on critical discussion of the work presented by Fatahi et al. (2013) and uses the opportunity to further clarify some important aspects of settlement/creep analyses in light of sample quality and parameter interpretation valid for the corresponding constitutive model.

Potassium Chloride as Ground Improvement in Quick Clay Areas – A Preliminary Study

Potassium chloride was added to low saline Norwegian post glacial clays to study its effect on strength parameters. The laboratory study was carried out on undisturbed sensitive clay samples from two locations in mid-Norway. The mechanical behaviour of sensitive clays is greatly influenced by their pore water ionic content. Adding salt changes the geotechnical properties of quick clay to such an extent that it appears as a total different clay. Salt migration is a time consuming process strongly dependent on diffusion through the soil. Deriving the effective diffusion coefficient from water content of 30–50 %, the clay will be de-sensitized over a length of 50 and 56 cm respectively after 1 year. Ground improvement with salt is done by installing salt wells. This study is part of a design project for such installations. The consumption of time depends on the distance between the wells, diffusion coefficient and maintenance of high concentration in the salt well.

A New Laboratory Procedure to Study Stress Relief in Soil Samples

During block sampling the in situ total stresses reduces to zero. This ultimately allows the soil sample to swell, leading to a weaker soil structure. In this paper, an attempt has been made to investigate this mechanism experimentally. In doing so, a new laboratory test procedure has been developed where the formation of a soil is simulated with a built in piezometer to study the stress changes in soil samples during and after sampling. The results show that the tested sample tends to lose a significant part of its residual effective stresses instantaneously, allowing the sample to swell.