Cut-slope versus shallow tunnel: Risk-based decision making framework for alternative selection

Choice between cut-slope and shallow tunnel alternatives is a common decision-making problem in the construction of highways or railways in mountainous regions. This paper outlines a risk-based decision making framework. Five indicators, including construction cost, duration, casualties, time overruns and economic loss, are adopted to evaluate the two alternatives, cut-slope and shallow tunnel. Landslide and tunnel collapse risks are analyzed quantitatively for these two alternatives. Based on reliability analysis, the probabilities of landslide and tunnel collapse are estimated. The extent of likely impacted area is delimited based on the failure potential. Then, according to the exposed elements within the impacted area, the consequences are estimated using Monte-Carlo simulation and event tree approach. A computer code was developed for quantitative risk assessment and multi-objective optimization, and an example is presented to illustrate the entire process.