The tunnel planned by the mountain tunneling method in urban areas is located in the soft rock mass in many cases. Soft rock has a mechanical characteristic which poses a design and construction top problems, such as strain-softening and dilatancy. However, the example of the tunnel excavation analysis which took these mechanical characteristics into consideration in practical work is now few. In this study, by reproducing the result of the triaxial compression test carried out in the usual geological survey by using numerical analysis, the parameter expressing these mechanical characteristics is obtained and the process applied to tunnel excavation analysis is proposed. This proposal has the feature in the point of having thought practicality as important, though expression of localization of deformation or material degradation which is the essence of the strain-softening characteristic is realized.

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