Abstract
This paper described three-dimensional effects of a support system and its evaluation for NATM. The investigation was carried out by means of three-dimensional FEM analysis considering progress of face. The investigation made it clear that the support effect of rock mass around tunnel was influenced by the difference of rigidity in the installed support system. Based on this result, we proposed a new three-dimensional support system which combines with a heavier support system with a lighter support system. This was regarded as a reasonable support system based on the concept of NATM. Finally, three-dimensional analysis results and the results obtained at the test construction site made it clear that the three-dimensional support system recommended here was useful.
