A rock slope just behind the Tarumi working face showed continuous contraction although excavation of limestone had been ceased at the face. In this study, a cause of this continuous deformation was investigated to assess stability of the rock slope by means of numerical analysis. 3-D finite element mesh for Ikura limestone quarry was created at several excavation stages. Then, both elastic and viscoelastic analyses were carried out to predict the rock slope deformation once elastic or viscosity moduli of rock mass were estimated by back analysis. Consequently, it was found that results of not elastic analysis but viscoelastic analysis using appropriate moduli were in good agreement with the measured results throughout the excavation stages. This reveals that the continuous contraction can be interrupted as creep deformation. The rock slope was assessed as safe because no accelerated deformation was observed.

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