Släntstabilitetsanalys med LEM och FEM - En jämförande fallstudie av en slänt i Vänersborg

Sammanfattning

Slope stability analysis is an important part of geotechnical engineering and is used to reduce the risk of landslides and slope failures in construction and infrastructure projects. Different calculation methods are commonly used to evaluate slope stability, where the most established approaches are the Limit Equilibrium Method (LEM) and the Finite Element Method (FEM). The purpose of this study is to compare slope stability calculations performed using SLOPE/W, PLAXIS, and hand calculations to evaluate how method choice affects the calculated factor of safety and the interpretation of slope stability. The study also examines differences in methodology, assumptions, and calculation principles between LEM and FEM. A case study approach was used where the same slope geometry and geotechnical parameters were analyzed with different methods. In SLOPE/W, the Morgenstern- Price and Spencer methods were applied together with the Entry and Exit and Grid and Radius search techniques. In PLAXIS, the Finite Element Method was used together with the Strength Reduction Method (SRM) to determine the factor of safety. Hand calculations based on simplified limit equilibrium principles were also performed for comparison purposes. The results show that all methods produced relatively similar factors of safety, indicating that the slope is generally stable regardless of the selected calculation method. However, FEM produced slightly lower safety factors compared to LEM, which may be explained by FEM’s ability to consider deformations and stress distributions in the soil mass. The hand calculations differed more from the numerical analyses due to simplifications and assumptions regarding the slip surface geometry. The study concludes that both LEM and FEM provided reliable results for slope stability analysis in this case study. LEM is efficient and suitable for simpler analyses, while FEM provides a more advanced and realistic representation of slope behavior and is therefore more suitable for complex geotechnical problems.