Uncertainties and tunnelling risks
The rockmasses surrounding an underground opening form a complex structure. Interpretations and extrapolations that are necessary to work out the geological setting in an underground excavation from the known conditions at the terrain surface, may introduce considerable uncertainties.
The rockmass.net site presents methods, descriptions and recommendations to improved collection of geological information for application in rock engineering and design. See 'Field observations'
Rock engineering and classification systems
An important requirement in rock engineering is that the method or tool used adequately covers the behaviour of the ground surrounding the tunnel or cavern. Rockmass classification systems play an important role here. How can such systems be applied correctly? What are the limitations?
Take a look at topics under 'Classification and design' to learn more about this.
Characterization and RockMass index (RMi)
Contrary to civil engineering and mining, the quality if the construction materials (rockmasses) in underground excavations cannot be measured by strength tests, but have to be characterized by several geological parameters. As a consequence of this, the RockMass index (RMi) has been developed, with input of the parameters that have the greatest influence on rockmass strength. Being based on strength properties the RMi values found can be used for various purposes.
The RMi system includes more parameter inputs than most of other systems. The structure is, however, such that RMi can be found also when only a few parameters are found. This is shown in Excel spreadsheets presented in 'Estimation'
Useful information is presented under 'Miscellaneous'