Slope stability analysis is an important technique for determining the long-term survivability of slopes. In order to do this, a number of factors need to be investigated. First, an understanding of the failure mechanisms of slopes is necessary. Second, it is possible to evaluate the effectiveness of proposed reinforcements. Finally, a study of the soil parameters can provide a more detailed analysis of the slope’s stability.
The most common approach to slope stability analysis is the limit equilibrium method. It is based on the principle of rigid block equilibrium analysis. However, there are several variations of this technique. Some of these variations can be used to analyze unsaturated soils, as well as for evaluating the stability of zoned earth dams.
Another technique to determine the stability of a slope is the factor of safety. This is a ratio of the maximum load that a slope can withstand to the actual load. When a slope has a factor of safety of less than one, it is considered unstable. Increasing the factor of safety may increase the slope’s strength or change its failure surface.
In addition to this, the type of soil can also affect its stability. For example, expansive soils during a rainfall period can develop a shallow layer that is susceptible to instability. Therefore, a thorough investigation of the soil is needed before a slope is redesigned. Depending on the soil’s geotechnical characteristics, a deterministic or finite element stress based method can be used. Alternatively, a bimodal hydraulic properties model may offer a better match to the data provided by field surveys.
To perform a slope stability analysis, the soil’s shear strength is measured and compared to a theoretical model. This allows the resulting shear strength criterion to be calculated. An empirical correction factor is applied to account for interslice shear forces. These two factors are then integrated to yield the factor of safety.
Deterministic methods for slope stability analysis can be divided into three categories: a stress-based method, a finite element method, and a nonlinear failure strength criterion. Each category of method uses a different set of parameters.
Stress-based methods include the finite element gravity increase and the finite element strength reduction methods. Both of these techniques are widely used in the industry. A nonlinear failure strength criterion is derived from a number of variables, such as the sliding body equilibrium conditions, the shear strength of the elements, and the elemental slice stress.
As a result, this method can be particularly useful in determining the stability of saturated clay slopes. However, this method requires laboratory tests under low confining stress conditions. Bimodal hydraulic properties are also required for evaluating the stability of shallow layers in expansive soils during the rainy season. These properties are calculated using the residual water content and pore water pressures, and pore water pressures can be defined by piezometric lines or using results from other GeoStudio finite element analyses.
Moreover, a comprehensive intrusive geotechnical investigation is needed for slopes that are found to be unstable. Such an investigation will consider the existing conditions, the design of new cuttings, and the monitoring of slope movements.