The Energy Needed to Completely Break Down Shear Strength in SW Swedish Clay Utilizing field vane test for determining remoulding energy
Examensarbete för masterexamen
Infrastructure and environmental engineering (MPIEE), MSc
Southwestern Sweden is an area which is prone to landslides due to sensitive clay. Several notable landslides have been recorded in the region, including the Surte landslide in 1950 and subsequent events in Göta, Tuve, Småröd, and Lökeberg. Clays with high sensitivity are sensitive to vibrations and disturbances, which could lead to a collapse of the microstructure and thus liquefaction. However, sensitivity alone does not provide a complete understanding of the risks of clay liquefaction and therefore development of the parameter is needed. The remoulding energy required to fully break down clay shear strength is a potentially important parameter, and further research is needed, particularly for Swedish-sensitive clay due to a gap in the research. Overall, this investigation addresses the need for a comprehensive understanding of clay behaviour and shear-strength degradation in sensitive clays, with the potential to enhance the knowledge base for stability assessments and mitigate the risks associated with the widespread distribution of sensitive clays. The investigation presented in this thesis aims to estimate the remoulding energy of clay using field vane tests. The methodology is based on the shear stress and shear strain behaviour of clay, where the strain energy involved in the remoulding is assumed to be the remoulding energy. Similarly, this behaviour can be obtained from vane shear tests. Seven locations from SW Sweden were analyzed, all close to Gothenburg. The results were correlated to soil parameters obtained from piston sampling. Additionally, the results were compared to findings of previous research on Norwegian, Canadian and Finnish clay. The thesis shows promising results in applying the field vane test to SW Swedish clay for determining the remoulding energy. The results for southwest-Swedish clay are of a smaller magnitude compared to previous research on Canadian and Norwegian clay. The remoulding energy shows correlations to several parameters but further research is suggested to develop the method and correlations. To further utilize the method it is important to conduct the field vane shear tests in a consistent manner. The findings lead to an increased understanding of the behaviour of clay during remoulding. This can in the future reduce uncertainties and lower the required safety factors for geotechnical engineering.
field vane test, remoulding energy, shear strength, sensitive clay, sensitivity