- Design Considerations
- Overall stability
- Long term stability (earthquake / rainfall)
- Water pressure
- Construction sequence (slope berm / inclination)
3D finite element analysis of slopes provides highly detailed results that are far more accurate than results obtained through conventional 2D limit equilibrium method analysis. However, the complexity and time-consuming nature of 3D finite element analysis has caused many engineers to prefer the limit equilibrium method.
GTS NX has a user-friendly modeling interface that has been specifically designed to overcome these limitations. These functions will enable you to use the finite element method to analyze slopes with unmatched levels of ease, efficiency, and precision.
GTS NX calculates all results that are essential to slope analysis: results for shear forces, deformations and factor of safety are all generated in detailed spreadsheet and model formats. You will also have the ability to analyze high-end slope projects that involve soil-structure interaction, analysis of slope stability during construction, and staged construction for embankments built on soft clay foundations.
Slope stability for an embankment or excavation is one of the most frequently dealt problems in geotechnical engineering. The slope always has a self-weight potential energy due to gravity and if external forces such as pore water pressure, applied load, earthquake, wave force etc. act on the slope, its stability is greatly affected.
Here, slope failure can occur if the internal shear stress due to the self-weight and external forces is greater than the shear strength of the slope soil. Calculating the safety for this slope failure due to shear stress and shear force is called Slope stability analysis.
The following slope stability analysis methods can be used on the GTS NX.
Strength Reduction Method (SRM): Nonlinear FEM-coupled strength reduction method
Stress Analysis Method (SAM): Method based on Nonlinear FEM and limit equilibrium theory
Strength Reduction Method (SRM)
Slope stability analysis using the finite element method is a numerical analysis method that analyzes the minimum safety factor and failure behavior using various shapes, loads and boundary conditions. In particular, the strength reduction method can be used to simulate the failure process without any previous assumptions(Griffith et. al. 1999; Matsui, 1990).
It can also be applied to 3D axis symmetric problems.
The strength reduction method gradually decreases the shear strength and friction angle until the calculation does not converge, and that point is considered to be the failure point of the slope. The maximum strength reduction ratio at that point is used to calculate the minimum safety factor of the slope.
Stress Analysis Method based on limit equilibrium theory (SAM)
This method first uses the finite element method to perform stress analysis on the slope and the safety factor for each various virtual slip surface, created from the assumptions of the limit equilibrium theory, is calculated based on the stress analysis results. Here, the calculated minimum safety factor of the various virtual slip surfaces becomes the safety factor, and the critical section is computed. The SAM method can only be used on the 2D environment.