A SUPPORT METHOD FOR DECISION-MAKING ON OPTIMAL PLACEMENT OF ROCKFALL PROTECTION STRUCTURES BASED ON ROCKFALL RISK ASSESSMENT

Abstract

 Probabilistic risk assessment is useful and practical because large uncertainties are involved in the assessment of damage and it is difficult to assess the damage deterministically. This study proposes a support methodology for optimal placement of protection structures against rockfall based on minimization of the total cost (the construction cost of protection structures and the risk) and shows an example of cost-benefit analysis for a model site. The risk is defined as the product of the probability of exceedance of the limit state and the consequence. A reproduction analysis of the rockfall behavior by the lumped mass method is performed to obtain input parameter of the model for the arrival position obtained from the large scale rockfall experiment. The rockfall hazard is evaluated based on energy of each rockfall when the falling rock reaches to the road. An optimal selection of protection structures against rockfalls is shown based on minimization of the total cost with budget constraint. Finally, we perform a cost-benefit analysis and indicate optimal placement of rockfall protection structures that minimizes the total cost with and without the budget constraint.