Theoretical investigation of the effect of stress on the performance of support systems based on Rock Mass Rating (RMR) support recommendations

Research output: Chapter in Book/Conference paperConference paper

Abstract

The Rock Mass Rating (RMR) classification system is widely used to design support systems for underground
openings. For underground openings, excavated in the same quality rock mass, the system proposes the
same support system independent from the depth of the opening. This study theoretically analyses the
performance of RMR proposed support for openings excavated in the same quality rock masses at different
depths.

A very comprehensive numerical modelling programme was conducted. Different case studies were
collected from current literature, presenting the results of the underground support design projects
conducted by different researchers. The quality of the rock masses range from poor to fair. Using the
collected information, numerical models of selected cases were constructed and internal support pressure
equivalent to RMR proposed support systems was applied. Next, the in situ stress conditions were changed
by assigning different depths and corresponding displacements were calculated. A critical strain criterion
was used to evaluate the relative performance of the RMR proposed support systems. The support pressure
necessary for keeping the strain below critical strain values was found iteratively for each case study, under
changing stress conditions. Finally, an empirical equation and graph were produced showing the
relationship between RMR, depth and the support pressure ratio, obtained by dividing necessary support
pressure by RMR proposed support pressure.

It was concluded that the pressure supplied by the RMR system is adequate for the openings excavated in
good quality rock masses and rock masses at shallow depth. However, as the rock quality decreases and the
depth increases, the support pressure provided by the proposed support system may not be adequate for
maintaining the opening’s stability.
Original languageEnglish
Title of host publicationProceedings of the 8th International Symposium on Ground Support in Mining and Underground Construction
EditorsErling Nordlund, Tristan Jones, Andreas Eitzenberger
PublisherLulea University of Technology
Number of pages9
ISBN (Print)978-91-7583-804-5
Publication statusPublished - 2016
Event8th International Symposium on Ground Support in Mining and Underground Construction - Lulea, Sweden
Duration: 12 Sep 201614 Sep 2016

Conference

Conference8th International Symposium on Ground Support in Mining and Underground Construction
Abbreviated titleGround Support 2016
CountrySweden
CityLulea
Period12/09/1614/09/16

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