Setting Basic Parameters of Slope Stability Analysis
The safety factor analysis is based on the assumption that the total load applied to the soil/rock body is introduced in a single load step. The actual factor of safety is evaluated using the method of reduction of strength parameters c, φ. Regarding this the factor of safety is defined as a scalar multiplier that reduces the original parameters c, φ to arrive at the state of failure.
Mathematically, the factor of safety is expressed as:
the original value of the angle of internal friction
the value of the angle of internal friction at failure
Searching for the critical value of the factor of safety requires a systematic modification (reduction) of strength parameters c, φ leading to failure. In the framework of the NRM the state of failure is determined as the state for which the solution fails to converge. The process of searching for critical c, φ is driven by the following parameters.
- Reduction - reduction factor (scalar multiplier) to reduce parameters c, φ. During the course of analysis this parameter is progressively updated.
- Min. reduction factor - the limit value, below which the value of reduction factor should not fall during the searching process. This parameter ensures that the computation will not continue for needless low values of the reduction factor. It is one of the parameters to terminate the searching process.
- Reduction of soil parameters - this parameter allows us to define which of the parameters c, φ should be reduced. The default setting assumes that both parameters are reduced at the same time.
Basic parameters of slope stability analysis