In situ ground improvement by deep mixing the soil with stabilising agents or binders as lime, cement, cement kiln dust or a combination of these is the most common method applied in the Nordic countries. In Norway, soil stabilisation with deep mixing has been applied to soft-to-medium stiff clays with sensitivity ranging from about 5 to over 100. This paper presents a large database of laboratory results from laboratory-stabilised Norwegian clays. For example the data show that shear strength of the stabilised clays decreases when the water-to-binder ratio (i.e. total clay water-to-binder content ratio) increases, and that the stiffness development is mainly controlled by time. Some observations from more advanced laboratory testing on samples taken from stabilised columns in the field highlight the anisotropic behaviour of the stabilised clays and the increase in strength with in situ stresses. The data presented can be used as a guide on the selection of binder mixes for specific project applications and it should always be supplemented by testing on site-specific laboratory-mixed specimens.

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As part of the construction of a new E6 highway between Jaktøyen and Storler in Trondheim, Norway, an area for performing full-scale field-testing of lime cement columns was defined. The soil conditions in the area cover non-sensitive clay to about 6-8 m over a silty quick clay down to at least 30 m. The aim of the full-scale field-tests was to assess how lime-cement columns would perform in a very sensitive clay (i.e. quick clay). The present paper describes the results from field and laboratory tests to characterize the field-testing site, as well as descriptions and field observations regarding the installation and results from testing of lime cement columns. The results are also compared to results of tests on laboratory mixed specimens of stabilized clay. Based on the data from the field trials, it was established a characteristic strength of 425 kPa (for 90 kg/m3 of binder) for the stabilized silty quick clay after two months which is a significantly higher value than the one used in the standard practice in Norway.

Mitigation actions related to quick-clay slopes often induce undesirable changes to the terrain that may have negative impact on developed areas and local biodiversity. Soil improvement may prevent this. Lime-cement piling causes temporarily reduced slope stability and substantial climate-gas emissions. Less climate-gas emissions are associated to the production of potassium chloride (KCl). KCl improves the post-failure properties of quick clay so it renders not quick and may serve as an alternative to current landslide-mitigation. The mechanisms in this chemical process is well documented, but there exist no installation procedures for KCl wells, nor knowledge on cost/benefit or climate-gas emissions. This paper presents two installation procedures of KCl wells, and studies showing that the climate-gas emissions are far less than installing lime-cement piles. Further development of cost-effective installation procedures is needed to justify application of KCl wells in quick-clay areas.