Rock mass has many discontinuities and irregular initial stress conditions due to various geophysical and geological activities. Because the underground structure has many unreliable factors in design stage, it is required to predict discontinuities ahead of tunnel face during tunnel construction. By monitoring and analyzing 3-dimensional absolute displacement during tunnel excavation, it is possible to predict discontinuity zones ahead of tunnel face. This paper presents results of the analysis of 3-dimensional displacement obtained from 3-dimensional numerical simulations used for assessing the effect of discontinuity zones on monitoring data. The influence of fault zones, cavities, and in situ initial stress on the 3-dimensional tunnel movement is evaluated.