One approach in definition of acceptable level of risk for slopes in hard rocks

Abstract

Slope stability analysis in hard rocks is one of the most complex tasks in geotechnical engineering. It requires application of specific design principles in order to find a way to incorporate all uncertainties coming from geological, geotechnical, economic and social aspects. In the frame of this article are presented the basics of one approach that shows how is possible to link the acceptable level of risk with the values of Factor of Safety or Probability of Failure. The methodology is supported with some results from stability analyses performed for slopes on the access road to dam "Sveta Petka" in R.Macedonia and some other case histories. Based on these analyses, the article gives some new proposals in definition of acceptable (tolerable) level of risks using also criteria of probability of failure, potential loss of life and economic impacts.

One method for defining an acceptable level of risks in tunneling

“…In order to explain the concept further here, we present some charts in Figure 8. and Figure 9, which were given by [8].…”

“…Finally, in Table 4, we are presenting some ideas to define some acceptable risk levels according to [8], modified slightly by the authors of this article. The motivation for this modification was the fact that the existing recommendations take into consideration only temporary mine openings, but not the unsupported temporary excavations for other structures presented in Table 4.…”

“…in Hong Kong [8] If the risk falls into the unacceptable zone ( Figure 1), it must be avoided or reduced, irrespective of the benefits, except in extraordinary circumstances. If the risk falls within the ALARP or tolerability region, then the cost may be taken into account when determining how far to pursue the goal of minimizing risk or achieving safety.…”

“…Concepts of determining the acceptable level of risk with a combination of the safety factor and the probability of failurea), b) and c) combinations from table Concepts of determining the acceptable level of risk a) Probability of failure -Number of deaths b) Probability of failure -Potential economic costs[8] …”