Investigating the relationships between rock mass classification systems based on data from mechanized tunneling projects in Iran.

Rock mass classification systems are valuable tools for estimating design parameters of rock engineering projects. In some cases, due to the lack of enough geological data, it may not be possible to use a specific classification system. Many researchers have attempted to develop empirical correlations between classifications. However, these relationships are not applicable in all geological conditions and are highly site specific. Hence, it is necessary to introduce different geology-specific empirical relationships. In this paper, geological and engineering geological data from 107 sections of three mechanized tunneling projects, constructed in different geological zones of Iran, were collected, screened, and compiled in a database. To take into account the engineering geological conditions, the collected data were first categorized based on the conditions of rock masses in the tunnels. Two important parameters of lithology and rock mass structure were the basic criteria for categorizing the collected data. Then, the relationships between different classifications including RMR, Q, and GSI in categorized engineering geological conditions were investigated. In addition, for the first time, some empirical relationships between usual rock mass parameters and less-known parameters, which apply in the NTNU model (proposed for predicting TBM performance), were developed to facilitate the application of this model. Statistical analysis of the developed relationships shows that the geological characteristics are very important in development of these relationships. Parameters such as presence of clayey and foliated rocks, thickness of beds, and number of discontinuity sets are some of the factors that affect these relationships. [ABSTRACT FROM AUTHOR]