A risk-based approach for the design of rock slopes subject to multiple failure modes-illustrated by a case study in Hong Kong

These risks were converted into design factors of safety using the likely numbers of failures per mode and per section (more possible failures means that each possible failure location requires a higher factor of safety to achieve the overall risk objectives). Required design factors of safety from this approach were typically in the range 1.2-1.8 compared with a normal requirement in Hong Kong of 1.4.