Abstract
The mechanical efficiency of a thin flexible tunnel support system such as shotcrete lining and rock bolts is investigated on the basis of experimental works. At first, model tests of tunnel excavation in which shotcrete lining and rock bolts were simulated by thin papers were carried out in a dry sand ground. It was found out that even if so flexible thin paper closed ring lining has a remarkable effect on the tunnel stability and that the effect of rock bolts appears only when they are placed to get into the outside of a plastic zone developed in the surrounding ground. A circular tunnel excavation was simulated by shrinking a metal ring in an aluminum rod mass and the development of a loosened zone in the ground due to tunneling was discussed. (Author abstract)
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