10th Asian Regional Conference of IAEG (2015)

RMR and SMR as Slope Stability Preliminary Studies
of Rajamandala Limestone Mine Area
Ilham PRASETYA(1), Rizqi NARENDRA(1), Agus WIRAMSYA(2), Irvan SOPHIAN(3),and Dicky MUSLIM(3)(1) Undergraduate of Geological Engineering Faculty, Padjadjaran University, Indonesia
E-mail: ilhampb160@yahoo.co.id(2) Postgraduate of Geological Engineering Faculty, Padjadjaran University, Indonesia(3) Geological Engineering Faculty, Padjadjaran University, Indonesia
Abstract
Rajamandala Limestone in Padalarang area in Indonesia has a long history of mining andexploitation. Most Rajamandala Limestone mining is performed in open-pit. Slope stability isoften a major issue in an open-pit mine. The stability of the open-pit mine slope must be
maintained so as not to disrupt the mining process. Rock Mass Rating (RMR) has been widelyused as a method of classifying the strength of the rock mass. RMR values in this study derived
from observations of the rock mass characteristics directly in Padalarang area at three different
mine sites and testing of the materials of intact samples in the laboratory. RMR values are thencorrelated into Slope Mass Rating (SMR) which is a system of classification of a rock slope.
The study showed that the Rajamandala Limestone Mine area has RMR values of 66-71 andincluded in the class II or Good Rock and SMR ranged between 61° - 72° and belong to Good
Slope class.
Keyword: Rajamandala Limestone, Open Pit Mining, RMR, SMR

2. RMR and SMR

1. Introduction
Rajamandala Limestone in Padalarang area inThe RMR (Rock Mass Classification) wasIndonesia has a long history of mining and exploitation.

developed By Bieniawski during 1972 - 1973Most Rajamandala Limestone mining is performed in(Bieniawski, 1973). It was modified over the years asopen-pit. Slope stability is often a major issue in an

more case histories became available and to conform

open-pit mine. The stability of the open-pit mine slopewith international standards and procedures (Bieniawski,

must be maintained so as not to disrupt the mining1979). Due to the RMR system having been modifiedprocess. This paper aimed to perform how to correlate

several times, and since the method is interchangeablyrock mass observations data from field to RMR andknown as the Geomechanics Classification or the RockSMR and use it as mining slope stability preliminary

Mass Rating system, it is important to state that thestudies.

system has remained essentially the same in principle

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10th Asian Regional Conference of IAEG (2015)

despite the changes (Bieniawski, 1989). The following

suggest the SMR value as follows :discussion is based upon the 1989 version of theSMR = 35 ln RMR-71(2)classification (Bieniawski, 1989). The following six

3. Laubscherr (1975, in Djakamihardja & Soebowo,

parameters are used to classify a rock mass using the1996) discusses the relationship of RMR and SMR as

RMR system :follows :Table 1. Laubscherr relationship of RMR and SMR

1. Uniaxial compressive strength of rock material.
3. Spacing of discontinuities

RMR Total
Value

SMR,
recommended
slope angle

4. Conditions of discontinuities

81 - 10075°

5. Groundwater conditions

61 - 8065°

6. Orientation of discontinuities

41 - 6055°

21 - 4045°

0 - 2035°

2. Rock Quality Designation (RQD).

2. Methodology
RMR

valuesinthisstudy

derivedfromobservations of the rock mass characteristics directly in
Padalarang area at three different mine sites (X01, X02,X03) and testing of the materials of intact samples inthe laboratory.

Fig 1. Sample of a rock mass with discontinuities (Hoekand Bray, 1981, in Wyllie 2005)
The RMR system is presented in Table 2. Each ofsix parameters is assigned a rating corresponding to thecharacteristic of the rock. These ratings are summed togive a value of RMR which lies between 0 - 100.
The Slope Mass Rating (SMR) is the applicationof the RMR to estimate the angle of slope stripping.
Some methods of mathematical calculation of the SMR
from RMR value has been developed by several authors,
here are some theme :1. Hall (1985, in Djakamihardja & Soebowo, 1996),
providing the SMR value as follows :SMR = 0.65 RMR + 25

Fig 2. Study area (Courtesy of Google Maps, 2015)
Figure 1 shows the spacing, conditions, andorientation of discontinuities in a jointed rock mass.

(1)

2. Orr (1992, in Djakamihardja & Soebowo, 1996)2

10th Asian Regional Conference of IAEG (2015)

Table 2. Classification parameters for RMR

The strength value of rock material in this study iscalculation is :RQD = 100 (0.1 λ + 1) e-0.1λobtained from point load test to each samples of intact(3)rock from field observation in laboratory. The RQD

Where λ is ratio between the amount ofvalue in this study is also obtained by direct

discontinuities passed by scan-line and the length ofmeasurement in field using scan-line method which isscan-line

introduced by

Hudson, 1979 (Wyllie, 2005), theThe obtained RMR values then correlated into

Table 3. Summary of RMR ValueSLOPE X01
Limestone, medium sizegrained, dark grey, very
hard, low permeability,
low slacking potential

SLOPE X02
Limestone, finegrained, pale brown,
very hard, lowpermeability, low

SLOPE X03
Limestone, fine grained,
pale brown, very hard,
low permeability, lowslacking potential

Strenght of Intact Rock Material (PointLoad Strenght Index (Mpa))

1.04

3.41

1.38

RATING

474

98.56%

73.40%

98%

Lithology Description

GroundWater

Conditions of Discontinuities

RQD (Hudson, 1979, in Djakamihardja &Soebowo, 1996))
RATING201320Spacing of Discontinuities (m)

3.16

1.95

1.2

RATING

201515

Discontinuity Length (m)

5.45

2.49

5.35

RATING

242

Separation (cm)

4.45

0.5

4.18

RATING

000

Roughness

Slightly RoughSmoothSlightly RoughRATING

313Soft (<5mm)

Soft (<5mm)

None

RATING

262Weathering

Slightly Weathered

Slightly Weathered

Slightly Weathered

RATING

555Flow

No Water Flow

No Water Flow

No Water Flow

General Conditions
RATING
TOTAL

Completely Dry
1571

Completely Dry
1566

Completely Dry
1566

Infilling (gouge)

310th Asian Regional Conference of IAEG (2015)

SMR using Hall, Orr, and Laubscherr method. So, inangle, it proved by the fact in the field on sites X02 andeach slope we have three values from three different

X03 that their overall slope ranges between 52° - 55°

method that can be used to estimate the slope stripping(Photo 1)
As the RMR and SMR value in this study isangle for each slope.

obtained from preliminary study based on surface data,
further investigation is required to obtain more

3. ResultFrom the observations of the Rajamandalaconclusive results.

Limestone characteristics directly at three different
mine sites (X01, X02, X03), we obtain that the study
area based on RMR classification system is consist ofsame rock class, which is Class II or Good Rock, andTable 4. RMR and SMR value in study area
RMRRatingsClass
Description
SMR
Laubscherr
Hall
Orr

X01
71
IIGood RockX01
60
66
61

X02
66
II
Good RockX02
55
67.3
72.9

X03
66
II
Good RockX03
55
67.3
72.9

based from three method (Laubsherr, Hall, Orr) thePhoto 1. Local failure at Site X03 with 53° slope angle

SMR value range between 55° - 72.9° (Table 3). The
descriptions and weighting for each RMR parameters ineach sites can be seen in Table 4.
From those three sites (X01, X02, X03), theobtained RMR and SMR values are similar. This can be
explained if we think geologically. We already knowthat these sites are consist of Limestone Members ofRajamandala Formation, which geologically they weredeposited together and had experienced the same
tectonic periods, this made this three sites has similar
physical characteristic from their strength into theirdiscontinuities properties.

Photo 2. Field documentation. (A) Site X02, (B) Fault
gauge at Site X02, (C) Joint sets in Site X01, (D)Calcite vein in site X03.

4. Conclusion
Based on RMR clasiffication system, in three
Referencedifferent sites, The Rajamandala Limestone mining area
has classified into Class II or Good Rock and has theSMR value range between 55° - 72.9°. The SMR value

Bieniawski, Z. T. (1989). Engineering Rock Mass

can not be the main criterion in determining a safe slope

Classification : A Complete Manual For Engineers andGeologist

4inMining,

Civil,andPetroleum10th Asian Regional Conference of IAEG (2015)

Engineering. Wiley_Interscience. ISBN 0-471-601721.
Bieniawski, Z.T. (1976). "Rock Mass Engineering"
Exploration for Rock Engineering, ed.

Z. T

Bieniawski, A. A. Balkema, Johannesburg.
Djakamiharja, A.S., & Soebowo, E. (1996). Studi
Kemantapan Lereng Batuan Pada Jalur jalan Raya
Liwa - Krui, Lampung Barat, Prosiding Seminar
Sehari Kemantapan Lereng Pertambangan ITB.
Direktorat

TeknikPertambagan,

Departemen

Pertambangan dan Energi.
Wyllie, Duncan. (2005). Rock Slope Engineering Civiland Mining 4th Edition. Spon Press Taylor & Francis
Group. London.

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