A probabilistic design approach for tunnel supports
Probabilistic calculation and design tools are not at present widely used for tunnel supports. A probabilistic approach, when it is possible to have sufficient data on the quality of the rock mass, leads to: a better understanding of the project risks; a more efficient geomechanical zoning; a more reliable estimation of the costs. This paper presents a probabilistic numerical approach for the design of primary tunnel supports, according to the hyperstatic reaction method. This approach considers the probabilistic distributions of the geomechanical index of the rock mass and of the mechanical parameters of the support material, using a Monte-Carlo technique. From the calculation results it is possible to obtain the probabilistic distribution of the support safety factors and then to design the supports on the basis of this probabilistic curve.
probabilistic approach probabilistic distribution safety factor quality index of the rock mass probability density function cumulative distribution function monte-carlo procedure geomechanical zoning of tunnel section rock masssupport interaction