This thesis compares foundation methods for buildings on low-strength, limited-depth soil. The study focuses on soil replacement and piling, specifically concrete and steel piles. The studyaims to answer the key questions about the possibility to use short piles on limited depth, cost-efficiency, and environmental impact of these methods. Geotechnical and structural calculations are used to assess the loads on the piles and evaluate their strength. WIN-statik Frame Analysis helps analyze deformations, moments, and stresses. The foundation transfers vertical loads to three piles, generating horizontal loads at the pile tops. However, the challenge lies in short piles in clay, which experience low earth pressure and may rotate due to bad stabilization. The analysis reveals that concrete piles are unable to transfer loads to solid rock effectively. Without fixed anchorage points, they are prone to rotation due to insufficient stiffness and lateral earth pressure. In contrast, steel piles are preferred because they can be drilled into the rock, providing fixed anchorage at the clay-rock transition and enabling them to withstand loads transferred through the foundation. Soil replacement is considered as an alternative method but proves economically expensive, approximately three times more than piling with steel piles. From an environmental standpoint, piling contributes only slightly more carbon dioxide emissions, about 0.4 tons, compared to soil replacement. Considering the significant cost advantage and minor environmental impact difference between soil replacement and piling, piling with steel piles is recommended as the optimal foundation method. Concrete piles are dismissed due to their instability. This choice ensures stability, cost-efficiency, and reduced environmental impact for buildings on low-strength, shallow-depth soil.

Structural design of piles with respect to buckling in Sweden is commonlymade in accordance with the calculation model from the Commission ofPile Research, PKR. A prerequisite for this model is that the elasticbuckling length of the pile is shorter than the physical length. For shortpiles this assumption might not be valid, meaning that anotherappropriate calculation model may be used instead. This situation occurswhen designing end-bearing piles in typical geological conditions foreastern Sweden, consisting of soft clay and shallow bedrock.This thesis compared the PKR-model with alternative models for thedesign of short piles. One of the alternate calculation models was a finiteelement model where Winkler springs represented the soil. It was used tosimulate cases with various diameters and undrained shear strengths.Furthermore, the results using the PKR- and FEM-model was comparedto calculations according to Eurocode 3 considering the pile as a freestandingcolumn. By the help of the FEM-model, a method to considergreater initial deflections in the Eurocode 3-model was also developed.In conclusion, the PKR-model was non-conservative for some of thetested cases. With some precautions taken for those cases, the model wasvalid to use for elastic buckling lengths up to two times the physicallength of the pile. The results from the Eurocode 3-model were bothconservative and non-conservative depending on the pile- and soilconditions. It was seen that the analytical models were not comparablesince they handle prerequisites and design assumptions in different ways.A sensitivity analysis was also made which resulted in suggestions forfurther research on the topic.