Investigation of Limit Equilibrium Method and Finite Element Analyses for Ground Anchored Slopes-PPT Presentation

PPT Presentation

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The presentation compares limit equilibrium methods (LEM) with the strength reduction finite element method (SRFEM) for analyzing ground-anchored slopes. SRFEM models soil deformation and progressive strength reduction, while requiring additional parameters—Young’s modulus, Poisson’s ratio, and dilation angle—beyond the cohesion, friction angle, and unit weight used in LEM. The presenters note that elastic parameters generally have limited influence on the calculated safety factor, while dilation angle can affect results.<br /><br />Across the examples, SRFEM safety factors were close to LEM results when a well-developed slip surface formed within the soil. However, SRFEM also revealed failure mechanisms that LEM may not capture, including a slip surface developing between the wall and soil.<br /><br />The analyses examined tieback prestress, soil stiffness, and tieback diameter. As the assumed safety factor increased during strength reduction, tieback tension rose substantially. The results indicate a limit to how much tieback force can be applied: for a 2.5-inch (6.35 cm) steel bar, a slip surface formed between the wall and soil at a tieback force of about 2,200 kN. LEM safety-factor estimates above this force may therefore be unreliable. Increasing tieback diameter can also affect the safety factor by allowing the tieback to carry more load.<br /><br />The presentation recommends FEM when deformation matters or when identifying the critical slip surface is important.

Keywords

limit equilibrium method

strength reduction finite element method

ground-anchored slopes

safety factor

slip surface

tieback prestress

soil deformation

soil stiffness

dilation angle

finite element analysis