Microstructural study of the deformation zones around a penetrating coned tip in silty soil

The change in soil microstructure around the penetrating probe during a cone penetration test is investigated. Backscattered electron images of polished thin sections prepared from frozen samples at the end of penetration are used. The images have a spatial resolution of 0.4 µm/pixel that allow a clear identification of grains and pore spaces. The statistical distribution of the change of particles orientation is analyzed for the zones around the cone tip and the shaft. Quantitative analysis of the change in porosity near the penetrating object is investigated. An increase in porosity and a decrease in the anisotropy of particle orientations from the cone and further out confirm that the soil deformation during CPTU in silt is a combination of compaction and dilative behavior that might influence the pore pressure distribution during penetration

Microstructural study of the deformation zones during cone penetration in silt at variable penetration rates

During conventional cone penetration testing in silt, the soil will normally be partially drained. If the penetration rate varies, time for drainage is altered and therefore the measured cone resistance and pore pressure will change. This paper studies the change in soil microstructure around the probe during cone penetration carried out at different penetration rates to investigate the failure mechanism and the processes controlling drainage in silt. Backscattered electron images of polished thin sections prepared from frozen samples at the end of penetration were used. Making use of advanced image processing techniques, the statistical distribution of particle orientations and the local porosity were investigated for the zones around the cone tip and the shaft. The spatial distribution of the measured microscale parameters in the region near the probe indicates that the soil deformation during CPTU in silt leads to the formation of both contractive and dilative zones. The macro response of the material, presented by the pore pressure and the cone penetration resistance measured during the test, results from the competition between these zones during penetration, which is shown to be dependent on the penetration rate

Micro-level investigation of the in situ shear vane failure geometry in sensitive clay

The circumferential failure surface of a shear vane in strain softening soft sensitive clay is studied. A set of shear vane experiments are performed in situ, where the sheared region is retrieved from the ground using an over-coring technique. By producing thin sections, the circumferential failure zone is revealed when viewed under a polarised light microscope. The failure zone is found to first evolve after reaching the peak global resistance. Its shape is not a full cylinder, but rather a rounded square. The structure of the shear zone is non-smooth and characterised by complex shear patterns of micrometre size

Quick-clay landslide mitigation using potassium-chloride wells: Installation procedures and effects

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.publishedVersio

Quick-clay landslide mitigation using potassium-chloride wells: Installation procedures and effects

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