The geomechanical classification RMR (Rock Mass Rating) by BIENIAWSKI. (1973) is very well known and sistematically applied in tunnels and dam foundations. The use of this classification in slopes poses many problems due to tile difficulties in stablishing the correction factors for slopes proposed by BIENIAWSKI. SMR (Slope Mass Rating) is a method for determining the adequate corrections factors to apply RMR to slopes (ROMANA, 1985,1986), This paper resumes data collected during two years research, analyzing slopes in calcareous rocks. The paper study the correlationship of the calculated SMR index vs. the real SMR deducted from the observed field behavior and the actual support measures installed in the slopes. The conclusion is that SMR index is slightly conservative; giving a forecast around half a class minor than the real one. Numerical errors in SMR are in the ± 5 order.
La classification geomechanique RMR (BIENIAWSKI,1973) est bien connue et l'on utilise systematicament pour les tunnels et les fondations de barrages. Mais l'utllisation de cette classification pour les talus et les pentes s'aveure tres difficile a cause de les problemes pour etablir les facteurs de correction proposes par BIENIAWSKI. SMR (Slope Mass Rating) est une methode que fixe les facteurs de correction pour RMR dans pentes et talus. (ROMANA 1985, 1986). La comunication resume les dates collectees pendant deux annees, dans 50 talus in roches calcaires. La communication etudie Ie SMR calcule vs. Ie SMR'q' ont peut deduire de l'etat real du talud et aussi les mesures de confortement apliees. Les conclusions sont que l'indice SMR est legerement pessimiste, en donnant une prediction de stabilite de l'ordre d'une demiclasse moins que la reale. L'erreur numerique peut s'etablir en ±_ 5 points.
Die RMR (Rock Mass Rating) Geomechanischeseinleitung von Bieniawski (1973) ist sehr bekannt und wird öffentlich bei Tunneln und Dammuterbauer benutzt. Die Anwerdung dieser Einleitung ar Böschungen ist aber problematisch, angesichtsder schwierigkeiten die Bieniawskikorrekturjaktoren festzustellen. Die- SMRmethode (Slope Mass Rating) rechnet die geeignte RMR Korrekturjaktoren fuer Böschungen (ROMANA, 1985, 1986). Diese Mitteilung jasst die Daten einer Zweijahrigegorschung, die Böschungen in Kalksteinen untersuchte. Die Mitteilung studiert die Korrelation zwischen der gerechneten SMRindex vs. der wircklichen SMR der von dem beobachteten Feldverhalten und den getroffenen Ausbauinaßnabren abgeleitet wird. Die Folgerung der Mitteilung ist daß, die SMR Index leicht konservativ ist, und ungejaahr eine Halfte Klasse unter die wirkliche voraussicht. Rechengehler in SMR sind etwa ±5 Punkte.
RMR "Rock Mass Rating" geomechanical classification (also called CSIR) was introduced and developed by BIENIAWSKI (1973, 1976, 1979). Two books (BIENAWSKI, 1984, 1989) deal extensively with RMR (and other geomechanical classification system). A good recent reference to RMR application to tunnels is BIENIAWSKI (1993), RMR has become a standard for use in tunnels and many professionals apply it to describe any rock mass.
ORR (1996) has give a good overview of the RMR use in slopes. LAUBSCHER (1976), HALL (1985), and ORR (1992) proposed different relationships between RMR value and limit angle for slopes. STEFFEN (1978) classified 35 slopes and concluded that "results had a statistical trend".
ROBERTSON (1988) established that when RMR> 40 the slope stability is governed both by orientation and shear strength of discontinuities whereas for RMR < 30 the failure develops across the rock mass.
In the 1976 version, the "rating adjustments for discontinuity orientations" for slopes were: very favourable 0, favourable -5, fair -25, unfavourable -50, very unfavourable -60. No guidelines have been published for the definition of each class. A mistake in this value can supersede by far any careful evaluation of the rock mass, and classification work becomes both difficult and arbitrary.
