In the Norwegian Sea, sea-bottom temperatures can be as low as –1.9°C in water depths greater than 1000m. In other deepwater areas, such as the Gulf of Guinea and the Gulf of Mexico, sea-bottom temperatures can be as low as 5°C. However, the standard practice up to now has been to carry out laboratory tests at room temperature (i.e. 20°C). Previous studies have indicated that testing at room temperature can result in laboratory measured strengths 10–20% lower than tests at in situ temperatures. Results from extensive parallel laboratory testing (at room temperature and at in situ temperature) on eight different types of soft clay are presented here, covering intact and remoulded specimens with the range of plasticity of 16–120%. This study quantifies the temperature effects on testing and storing of deepwater samples. The investigated soil parameters concentrate on the undrained shear strength (su) and preconsolidation stress (p'c). All the parallel tests showed that su increased on average of 2% to 40% when tested at cold temperature. With one exception, where a similar increase in measured p'c of 9% to 38% was observed. Recommendations are given for procedures for testing, transporting and storing deepwater samples to arrive at the closest possible representative soil design parameters for in situ conditions.
In the Norwegian Sea, sea-bottom temperatures can be as low as –1.9°C in water depths greater than 1000m. Due to the salt content of the pore water (typically about 30g/l), the soil does not freeze. In other deepwater areas, such as the Gulf of Guinea and the Gulf of Mexico, sea-bottom temperatures can be as low as 5°C. In connection with field developments in deep water, the use of low values of su and p'c can lead to foundation solutions that are unnecessarily conservative and costly.