Abstract
Generally, supports for mountain tunnels constructed by NATM apply “Standard support patterns” due to the results of geological survey. Under existing circumstances, there are many support pattern alterations under construction. In this paper, we investigate the situation of support alterations in tunnels constructed in Granite, Slate, Schist mountains, respectively. Results obtained from the investigation indicate that the elastic wave velocity of the ground is the most effective parameter in the preliminary design of supports, but constructed support patterns barely correlate it and supports tend to alterate more safely under construction. Still more, we tried to find the factor of alteration and make a proposal to improve reliability of preliminary support designs for tunnels.
