Strength and deformation characterization of Norwegian organic cohesive soil (gyttja)

Abstract

In several road projects in western Norway, it is common to encounter a soil consisting of mineral soils with an organic part and high water content. The organic soil is referred to as gyttja and the organic part originates from remains of plants and animals rich in fats and proteins. It is common to find up to 14 m thick soil layers containing gyttja. The amount of organic content is much lower than peats however this is observed to significantly alter the engineering property of mineral soils involving clay and silt. However, there exists no systematic study on characterization of strength and deformation properties of gyttja in Norway. As a result, it is a common practice to excavate and replace such soils. However, this shall not be a viable engineering solution as removal of organic soils gives a significant CO2 emission. This implies that it is important to find ways to deal with such types of soils apart from always replacing them. To achieve this, it is essential to establish engineering properties for characterization of strength and deformation behaviour of gyttja. This research work thus focuses on looking at these aspects based on extensive field and laboratory tests. Effect of cement as a stabilization method to improve strength is also experimentally looked at. Results are also compared with available data from literature documenting other countries experiences with organic soils. This work presents and discusses main trends, correlations and characteristics related to strength and deformation behaviours of Norwegian gyttja.