Historical Changes of Rock Mass Modelling and Numerical Technique and the Features of Those

A lot of methods have been developed in order to evaluate mechanical behavior of rock mass containing discontinuities. The methods can be classified roughly into three categories. First one is to model the rock mass which contains many and unspecific discontinuities by replacing it with an equivalent continuum. Second one is to analyze failure behavior of rock mass, modeling all of the discontinuities as they are, for the rock mass in which specific joints exist distinctly. Third one is to analyze formation of shear band as the result of successive development of micro fractures and accumulation of those, which depend on heterogeneity of rock mass.These numerical methods have been rapidly developed since the decade of 1960 when FEM analyses were introduced into rock engineering and computer came into wide use, and further development are still being carried out. Historical changes in development of the numerical methods and the significant features of those are described in this report.