RMR Bieniawski

The “Rock Mass Rating” (RMR) system by Z.T. Bieniawski [1]

Parameters

The following parameter descriptions are based on the 1989 version [2].

Strength

RMR Rating – Strength of Intact Rock Material

PLT [MPa]	UCS [MPa]	Rating
> 10	> 250	15
4–10	100–250	12
2–4	50–100	7
1–2	25–50	4
0.5–1	5–25	2
< 1	1–5	1
Use of UCS preferred	< 1	0

RQD

RMR Rating – RQD (%)

RQD [%]	Rating
90–100	20
75–90	17
50–75	13
25–50	8
< 25	3

Discontinuities Spacing

RMR Rating – Spacing of Discontinuities

Spacing of Discontinuities	Rating
> 2 m	20
0.6 – 2 m	15
200 – 600 mm	10
60 – 200 mm	8
< 60 mm	5

Groundwater

RMR Rating – Groundwater Conditions

Inflow per 10 m tunnel length [L/min]	Joint water pressure / Major principal stress	General conditions	Rating
None	0	Completely dry	15
< 10	< 0.1	Damp	10
10 – 25	0.1 – 0.2	Wet	7
25 – 125	0.2 – 0.5	Dripping	4
> 125	> 0.5	Flowing	0

Joint Condition

Persistence

RMR – Discontinuity Length (Persistence)

Description	Rating
< 1 m	6
1 – 3 m	4
3 – 10 m	2
10 – 20 m	1
> 20 m	0

Aperture

RMR – Separation (Aperture)

Description	Rating
None	6
< 0.1 mm	5
0.1 – 1.0 mm	4
1 – 5 mm	1
> 5 mm	0

Roughness

RMR – Roughness

Description	Rating
Very rough	6
Rough	5
Slightly rough	3
Smooth	1
Slickensided	0

Infill

RMR – Infill (Gouge)

Description	Rating
None	6
< 5 mm (hard filling)	4
> 5 mm (hard filling)	2
< 5 mm (soft filling)	2
> 5 mm (soft filling)	0

Weathering

RMR – Weathering

Description	Rating
Unweathered	6
Slightly weathered	5
Moderately weathered	3
Highly weathered	1
Decomposed	0

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RMR Versions

The RMR system has evolved over time, with modifications to parameter weightings across key publications. The table below summarizes these changes from 1973 to 1989 [3].

Evolution of RMR Parameter Ratings (1973–1989)

Ratings	1973 [1]	1974 [4]	1975 [5]	1976 [5]	1989 [2]
Rock Strength	10	10	15	15	15
RQD	16	20	20	20	20
Discontinuity Spacing	30	30	30	30	20
Condition of Joints	34	30	30	25	30
Groundwater	10	10	10	10	15
Orientation of Joints	-(3–15)	-(0–15)	-(0–12)	-(0–12)	-(0–12)

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GeoAssistant Implementation

Hola

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References

[1] (1,2)

Z. T. Bieniawski. Engineering classification of jointed rock masses. Transactions of the South African Institution of Civil Engineers, 15(12):335–344, 1973.

[2] (1,2)

Z. T. Bieniawski. Engineering Rock Mass Classifications: A Complete Manual for Engineers and Geologists in Mining, Civil, and Petroleum Engineering. Wiley, New York, 1989. ISBN 978-0-471-60260-8.

[3]

D. Milne, J. Hadjigeorgiou, and R. Pakalnis. Rock mass characterization for underground hard rock mines. Tunnelling and Underground Space Technology, 13(4):383–391, 1998. doi:10.1016/S0886-7798(98)00081-9.

[4]

Z. T. Bieniawski. Geomechanics classification of rock masses and its application in tunneling. In Proceedings of the 3rd Congress of the International Society for Rock Mechanics (ISRM), volume 2, 27–32. Denver, Colorado, 1974.

[5] (1,2)

Z. T. Bieniawski. Rock mass classification of jointed rock masses. In Z. T. Bieniawski, editor, Exploration for Rock Engineering, pages 97–106. A. A. Balkema, Johannesburg, 1976.