Temporary Tunnel Support Strategies: Optimization and Testing
When designing and constructing support systems for tunnels in weak ground, oftentimes a temporary support regime is utilized in order to provide provisional support until the final liner is installed. These support systems are primarily designed contingent upon the ground conditions that are anticipated. The assortment and arrangement of such support systems are many and involve but, are not limited to: umbrella arch support (i.e. forepoles), steel sets, rock bolts, inverts, shotcrete, elephant’s feet etc. (Figure 1). While much investigation has been conducted on each of these support elements separately, in isolation, the combined effect of such assortments has not been investigated fully. As well, when support elements have been individually assessed in the past, the resolution of strain monitoring has been quite coarse which has led to a partial understanding of related mechanisms involved with these support elements. There is then the potential to optimize this support with respect to the anticipated performance of such support while taking into consideration, performance, cost, and safety. On the material side, the mechanisms of ground/soil support interaction related to face or near-face reinforcement systems are poorly understood.