Abstract: It is well known that the correct division of engineering geological strata groups of rock mass is the basis of rock mass quality evaluation. When many soil layers were revealed, especially in large projects, it is necessary to divide the engineering geological strata groups of soil mass either. The division is helpful to show the geological structure of the site more clearly, make it convenient to generalize the engineering geological model and study geotechnical parameters on the basis of the model and is helpful to capture and evaluate the primary engineering geological problems. Furthermore, it is easier for the architects to understand and to apply to. Taking the Nanjing Metro for example, the issues of the division are discussed. Through the statistics of discrete data acquired from the divided strata groups and analyses on the engineering geological models and problems, the rationality and significance of the division is noticeable.

Key words: soil mass, engineering geological strata groups, Nanjing Metro