research article rock load estimation in development...

Research ArticleRock Load Estimation in Development Galleriesand Junctions for Underground Coal Mines A CMRI-ISM RockMass Rating Approach

Avinash Paul1 V M S R Murthy2 and Ajoy Kumar Singh1

1 CSIR-Central Institute of Mining and Fuel Research Dhanbad 826 015 India2Mining Engineering Department Indian School of Mines Dhanbad 826004 India

Correspondence should be addressed to Avinash Paul avinashpaul02gmailcom

Received 27 August 2013 Accepted 19 December 2013 Published 9 March 2014

Academic Editor Manoj Khandelwal

Copyright copy 2014 Avinash Paul et al This is an open access article distributed under the Creative Commons Attribution Licensewhich permits unrestricted use distribution and reproduction in any medium provided the original work is properly cited

Rock mass rating (RMR) plays important role in design and selection of support system (Ghosh 2000) For stability assessment ofrockmass it is very important to know the amount of rock loadmobilized around the development gallery which is estimated usingRMR (Singh et al 2003 Barton et al 1974 Bieniawski 1984 andGhosh et al 1992) In Indian coal mines CentralMining ResearchInstitute-Indian School of Mines rock mass rating (herein after referred to as CMRI-ISM RMR) is mostly used for formulatingdesign guidelines for supports In this paper an attempt has been made to correlate CMRI-ISM RMR values and rock load ofgalleries and junctions for different gallery widths ranging from 36m to 48m at different densities of roof rocks The proposedempirical expression can help in quick design of support system for underground coal mines working in the same regime

1 Introduction

Roof and side falls in underground coal mines constitute themajor reason for underground accidents and fatalities eventoday Statistical analysis reveals that the share of roof andside falls contributes to 285 of the fatalities [1 2] Afterthe development of CMRI-ISM RMR an empirical approachfor rock load estimation and support design in Indianunderground mine roadways the support related accidentshave started declining though they still haunt the miningengineers every now and then The RMR reflects the qualityof roof in numeric terms and quantitative terms It is based onfive parameters and obtained after summation of all those fivevalues The obtained RMR is adjusted for different workingconditions and then used to estimate the rock load mobilizedaround the galleries and junctions for design of supportsystem for underground coal mines

2 Study Area of Research Work

The case studies incorporated in this paper are taken fromdifferent mines of Bharat Coking Coal Limited and Tata

Steel Limited situated in Jharia coalfield (Figure 1) [3] Jhariacoalfield located in Dhanbad district of Jharkhand state isone of the largest coalfields in India that has been activelyassociatedwith coalmining activities formore than a centuryThe study area lies in the heart of Damodar valley alongthe north of Damodar river The coalfield is named after thechief mining centre Jharia situated in the eastern part of thecoalfield The coal basin extends for about 38 km in the east-west direction and a maximum of 18 km in the north-southdirection covering an area of about 450 km2

21 CMRI-ISM RMRmdashAn Overview Rock mass rating(CMRI-ISM RMR) [4ndash9] determined by CMRI-ISM Geome-chanical Classification System is the summation of the ratingsof five individual parameters The individual parameters andtheir maximum rating are provided in Table 1

Layer thickness is very important as delamination is amajor causative factor for deterioration of roof condition [5]For determining layer thickness thickness of bedding planeis measured if roof is sandstone In case of shale thickness ofbedding plane or thickness of lamination is measured In case

Hindawi Publishing CorporationJournal of MiningVolume 2014 Article ID 618719 9 pageshttpdxdoiorg1011552014618719

2 Journal of Mining

0 312

(km)

Jharia Coalfield

New Delhi

JharkhandMumbai

Chennai

Son River

DaltonganjBarwadih

Lohardaga

GayaGT Road

Hazaribag

Ranchi

Damodar River

MuriPurulia

Gomoh

AdraDamodar River

Barakar River

GT Road

Asansol

Dhanbad

JhariaCoalfield

Up Bihar

JharkhandMP Jharia

BengalW

N

Orissa

(1)(2)

(3)(4)

(5)

(6)

0 16 48

(km)

28∘

Kolkata

(1) Raniganj(2) Jharia(3) Bokaro(4) North Karanpura(5) Daltonganj

(6) RamgarhRail lineRoadRiver

84∘0998400

85∘0998400

86∘0998400

87∘0998400

84∘0998400

24∘0998400 24

∘0998400

85∘0998400

86∘0998400

87∘0998400

Figure 1 Location of Jharia coalfield in India

Table 1 Parameters of CMRI-ISM rock mass rating

Parameter Maximum ratingLayer thickness (cm) 30Structural features 25Weatherability (1st cycle slake durability index) 20Compressive strength (Kgcm2) 15Groundwater condition (mLmin) 10

of coal roof there are different small bands or layers of coalwhich are measured as layer thickness

Structural features are geological structures which causeroof deterioration and constitute major faults slips jointsand other sedimentary features like sandstone channel plantimpression and so forthWater percolation is themajor prob-lem in Indian coal mines thus weatherability is importantbecause many coal measure rocks become weak or disinte-grate due to weathering especially in presence of water Themeasure for this parameter is the 1st cycle slake durabilityindex (SDI) determined by slake durability apparatus [10]

Compressive strength of rock is determined in the laboratoryas per Bureau of Indian Standards [11]

Groundwater seepage is measured by drilling a 15 to18m long hole in roof and thereafter collecting the waterpercolation through it The rate of percolation is expressedin mLmin

Adjustments for depth lateral stress induced stressesmethod of excavation and gallery span aremade for account-ing their positive neutral and negative contribution to RMRvalues as given in Table 2

After due adjustment adjusted RMR is used for estima-tion of rock load in galleries and junctions from the followingequations

Rock load in roadways (tm2)

= 119861 sdot 119863 sdot (17 minus 0037RMR + 00002RMR2) (1)

Rock load in junctions (tm2) = 5 sdot 11986103 sdot 119863(1 minus RMR100)2

(2)

Journal of Mining 3

Table 2 Adjustment factors for RMR

Parameter Adjustment ofRMR

AdjustedRMR

(1) DepthLess than 250m Nil RMR times 10250ndash400m 10 reduction RMR times 09400ndash600m 20 reduction RMR times 08More than 600m 30 reduction RMR times 07

(2) Lateral stressesSmall 10 reduction RMR times 09Moderate 20 reduction RMR times 08High 30 reduction RMR times 07

(3) Induced stressesNo adjacent workingin the seam Nil RMR times 10

Extraction areas within20ndash40m in the same seam 10 reduction RMR times 09

Extraction areas within10ndash20m in the same seam

Up to 30reduction

RMR times (07to 08)

Working with 10ndash20 parting 10 reduction RMR times 09Working with3ndash10m parting

Up to 30reduction

RMR times (07to 08)

(4) Method of excavationContinuous miner 10 increase RMR times 11Undercut and blasting Nil RMR times 10Blasting off the solid 10 reduction RMR times 09

(5) Gallery spanLess than 48m Nil RMR times 10

48ndash60m 10ndash20reduction

RMR times (08to 09)

where RMR = rock mass rating 119861 = roadway width (m) and119863 = dry density (tm3)

3 Rock Load Estimation for Galleriesand Junctions Some Field Studies

Field studies were conducted in differentmines andRMRwasdetermined For determination of RMR three parametersnamely layer thickness structural features and groundwaterwere collected during geotechnical studies of roof rocks in themine site Compressive strength and 1st cycle slake durabilityindex were determined in the laboratory The details ofinvestigations carried out are provided in Table 3 The casesare classified based on gallery width that is 36m 42m and48m respectively

4 Analysis of Investigations

41 Mine Development Galleries The correlation analysisdone between CMRI-ISM RMR and estimated rock load ofgalleries (with the suggested rock load equation (1)) wasstatistically analyzed using least square regression method(Table 3) Equations have been developed for 36m 42m

55 56 57 58 59 60 61 62RMR

15

16

17

18

19

20

21

95 confidence

Rock

load

(tm

2)

RMR versus rock load (36m gallery width)Rock load = 72478 minus 093

Correlation r2 = 09

0

4

4 lowast RMR

Figure 2 Correlation between RMR and rock load for 36m gallerywidth

30 35 40 45 50 55 60 65RMR

14161820222426283032343638

95 confidence

Rock

load

(tm

2)

42m gallery width)Rock load = 5914

Correlation r2 = 098

4 minus 00675 lowast RMRRMR versus rock load (


and 48m gallery width using different range of densitiesThe equation of best fit line and coefficient of determination(R2) were determined for each regression (Figures 2ndash4)Minimum R2 value obtained in this analysis is 086 for 48mgallery width The results of regression equation and thecoefficient of determination are presented in Table 5 A linearrelationship was observed in all three cases

Correlation between RMR and Rock Load for 36m GalleryWidth See Figure 2



42 Junctions The correlation analysis done between CMRI-ISM RMR and estimated (estimated using (2)) rock load ofjunctions was statistically analyzed using least square regres-sionmethod (Table 3)The equations have beendeveloped for

4 Journal of Mining

Table 3 RMR and rock load estimation for galleries and junctions for different mines

S number Name of the mine Density(tm3) RMR Rock load in gallery

(tm2)Rock load in junction

(tm2)For 36m gallery width where roof rock density varied from 22 tm3 to 24 tm3

variation of RMR and density from minimum value is up to 96 and 95 respectively1 Huriladih 219 576 183 2892 Block IV 221 603 156 2553 Sudamdih 24 612 159 2654 Huriladih 223 558 207 319

For 42m gallery width where roof rock density varied from 127 tm3 to 255 tm3

variation of RMR and density from minimum value is up to 75 and 875 respectively1 Bagdighi 255 6205 186 2822 Jogidih 238 612 185 2763 Khas Kusunda 218 587 199 2864 Khas Kusunda 232 63 159 2445 Damoda 24 612 186 2776 Sendra Bansjora 205 558 222 3077 Dobari 182 604 149 2198 Tetulmari 237 608 188 289 Sendra Bansjora (Bot) 143 3807 349 42210 Gopalichack 148 433 294 36611 Kusunda 136 367 349 41912 Bagdighi 136 408 29 36613 East Bhuggatdih 152 424 313 38814 Damoda (BJ Pit) 127 36 334 415 Amlabad 144 416 306 37816 Alkusha 149 432 297 36917 Nichitpur 154 424 317 39318 Industry 141 369 359 43219 Ramkanali 144 416 307 37820 Mudidih (Pit number 3) 151 4374 294 367


variation of RMR and density from minimum value is up to 514 and 764 respectively1 Godhur 148 45 32 352 South Balihari 139 424 327 363 Huriladih 135 416 328 364 Godhur incline 147 432 335 385 Mahamaya mine SECL 19 612 158 226 Churcha mine SECL 24 567 282 367 Shivani mine SECL 215 576 24 308 Baherabad mine SECL 226 63 176 24

junctions formed with 36m 42m and 48m wide galleriesusing different range of densities The equation of best fit lineand coefficient of determination (R2) were determined foreach regression (Figures 5ndash7) Minimum R2 value obtainedhere is 072 for junctions formed with 48m gallery widthThe results of regression equation and the coefficient ofdetermination are presented in Table 5 A linear relationshiphas been observed in all three cases

Correlation betweenRMRandRock Load for Junctions Formedwith 36mWide Gallery See Figure 5



Journal of Mining 5

Table 4 Estimated rock load for 36m 42m and 48m wide gal-leries and junctions

Estimated rock load(CMRI-ISM RMR)

Estimated rock load(best fit equation)

Gallery(tm2)

Junction(tm2)

Gallery(tm2)

Junction(tm2)

18 28 21 29For 36mwidegalleries

15 25 18 2715 26 17 2620 31 22 3118 28 17 26

For 42mwidegalleries

18 27 18 2619 28 19 2815 24 16 2518 27 18 2622 30 21 2914 21 18 2718 28 18 2634 42 33 4029 36 30 3734 41 34 4129 36 31 3831 38 30 3833 40 35 4130 37 31 3829 36 30 3731 39 30 3835 43 34 4130 37 31 3829 36 29 3732 35 31 36


32 36 33 3732 36 34 3833 38 33 3715 22 19 2728 36 23 2924 30 22 2917 24 18 26

5 Correlation of Estimated Rock Load forGalleries and Junctions

The estimated rock load which is obtained from CMRI-ISMRMR is correlated with the estimated rock load determinedfor both galleries and junctions which is arrived at by bestfit equations in the analysis for 36m 42m and for 48mgalleries as well as for junctions formed with 36m 42mand 48m galleries (Table 4) The estimated rock load fromdeveloped best fit equations is presented Table 5 Here alsovery good correlation is obtained in all the cases which areshown in the figures (Figures 8ndash13)The error in the estimatedvalue is represented by the distance of each data point from

40 42 44 46 48 50 52 54 56 58 60 62 64141618202224262830323436

RMR

95 confidence

Rock

load

(tm

2)

Rock load = 64493 minus


00729 lowast RMR48m gallery width)RMR versus rock load (

Figure 4 Correlation between RMR and rock load of 48m gallerywidth

094

55 56 57 58 59 60 61 62252627282930313233

RMR

Rock

load

(tm

2)

36m junctions)Rock load = 92159 minus

Correlation r2 =

95 confidence

01089 lowast RMRRMR versus rock load (

Figure 5 Correlation between RMR and rock load of junctions(36m wide galleries)

the 1 1 slope line A point lying on the 1 1 slope line shows anaccurate estimation whereas points away from the line showthe error as shown in Figures 2ndash12 Equations for statisticalanalysis are selected so that the coefficient of determination(R2) value should be more than 072 in all six cases which isacceptable for establishment of correlation equations

Correlation between Estimated Rock Load for 36mWide Gal-lery and Junctions See Figures 8 and 9



6 Studentrsquos 119905-Test

The significance of 119877-values can be determined by the 119905-testassuming that both variables are normally distributed and theobservations are chosen randomly The test finds the 119905-valueand check the significance of the input values of the equationsIf the 119875 value (level of significance ) is less than 005 thenit is said that the data which is used is statistically significant

6 Journal of Mining

Table 5 Regression equations between CMRI-ISM RMR and rock load of galleries and Junctions

Case number Parameters Regression equations 1198772 value

1 RMR versus rock load(for 36m wide galleries) RL(galleries) = 72 minus 009 lowast RMR 094



4 RMR versus rock load(for 36m wide junctions) RL(junctions) = 92 minus 010 lowast RMR 094



Table 6 119905-test for independent samples (variables treated as independent samples)

S number Group 1 versus group 2 Meangroup 1

Meangroup 2 119905-value df 119875

(level of significance) Remarks

1 RMR versus calculated rock load(gallery width 36m) 675 218 20 8 005 Number of data

are less2 RMR versus calculated rock load

(junctions) 675 226 20 8 005


are good4 RMR versus calculated rock load

(junctions) 510 81 74 40 0000000


are moderate6 RMR versus calculated rock load

(junctions) 513 32 148 14 0000000

30 35 40 45 50 55 60 6520242832364044

RMR

Rock

load

(tm

2)

RMR versus rock load (junctions)Rock load = 63397 minus

096Correlation r2 =

95 confidence

00602 lowast RMR


119905-test used for comparing the means of two variables even ifthey have different number of replicates In general term 119905-testcompares the actual difference between twomeans in relationto the variation in data The formula for the 119905-test is the ratio

in which the numerator is just the difference between twomeans or average and denominator is a measure of variabilityor dispersion Consider

119905 =( 119879minus 119862)

radicVar119879119899119879+ Var119862119899119862

(3)

From Table 6 it is seen that in all of the three cases the valueof 119875 (level of significance) is lt005 which is the value tocheck the significance of the input data whether they arestatistically significant or not Thus it may be concluded thata high degree of correlation has been seen between CMRI-ISM RMR and best fit equations estimated rock load valuesfor galleries and junctions Thus the obtained equationsare acceptable for future application in similar geo-miningregime

7 Predictability of the Derived Equations

An analysis is carried out to study the influence of varyingRMR on rock load estimated from best fit equations to assessthe behavior of the developed equations for the both galleries

Journal of Mining 7

0717

40 42 44 46 48 50 52 54 56 58 60 62 642022242628303234363840

RMR

95 confidence

Rock

load

(tm

2)


Correlation r2 =00556 lowast RMR48m junctions)RMR versus rock load (

Figure 7 Correlation between RMR and rock loads of Junctions(48m wide galleries)

and junctions with the varying width from 36m to 48m(Figures 14 and 15) It may be seen that in some case for theless gallery width the rock load obtained is on higher side forboth galleries and junctions when the gallery and junctionwidth were less (36m)This transition line was at RMR valueof 50 for galleries and 60 for junctions A normal trend ofreduced rock load was seen with reduced galleries width athigher values of RMR

8 Conclusion

(1) This study indicates that the rock load of galleries andjunctions of various coal measures rocks of India canbe estimated by using simple empirical relationshipsafter substituting only the value of RMR All the sixcases showed linear relationship with each other

(2) The empirical expressions for rock load estimation incoal measure roof rocks for 36m 42m and 48mgallery width are as follows

Rock Load (galleries of 36m)

= 72 minus 009 lowast RMR

1198772 = 094



1198772 = 098



1198772 = 086

15 16 17 18 19 20 211718192021222324

95 confidence

Calc

ulat

ed ro

cklo

ad (t

m2)

Actual rock load (tm2)

Actual rock load versus calculated rock load(36m gallery)


Figure 8 Correlation between estimated rock loads for 36mgalleries

25 26 27 28 29 30 31 32 33252627282930313233

Calc

ulat

ed ro

cklo

ad (t

m2)


Actual rock load versus calculated rock loadCorrelation r2 = 0947

95 confidence

Figure 9 Correlation between estimated rock loads for junctions

Rock Load (junctions of 36m)


1198772 = 095



1198772 = 096

Rock Load (junction of 48m)


1198772 = 072(4)

(3) Strong coefficient of determination was found in allthe six cases shown

(4) Developed equations are applicable for 36m 42mand 48m gallery width with density in the range of22 tm3ndash24 tm3for 36m gallery width 127 tm3ndash255 tm3 for 42 gallery width and 135 tm3ndash24 tm3for 48m gallery width

(5) Equations are practical simple and reasonably accu-rate to apply

8 Journal of Mining

14 16 18 20 22 24 26 28 30 32 34 36 382022242628303234363840424446

Calc

ulat

ed ro

ck lo

ad (t

m2)



Actual rock load versus calculated rock load(gallery width 42m)

95 confidence


20 22 24 26 28 30 32 34 36 38 40 42 44 462426283032343638404244

95 confidence

Calc

ulat

ed ro

ck lo

ad (t

m2)


Actual rock load versus calculated rock load (junctions)Correlation r2 = 09634


(6) This study coupled with judicious judgment canbe helpful for arriving at the initial estimates ofrock loads in development galleries and junctions ofunderground coal mines and thus can help in supportdesign with greater safety and stability for Indiangeomining conditions

(7) The variation in rock load behavior in different gallerywidths can be attributed to variation in roof rocksdensity and RMR range Lack of enough data setsalso lead to this variation thus pointing to the needfor including more data for realistic predictions Arelook into the parameters considered for rock loadestimation is also necessary tomakemore wholesomepredictions

Abbreviations

CMRI-ISM Central Mining ResearchInstitute-Indian School of Mines

RMR Rock mass ratingRL Rock loadBCCL Bharat Coking Coal Limited

(48 wide gallery)0865

14 16 18 20 22 24 26 28 30 32 34 361618202224262830323436

Calc

ulat

ed ro

ck lo

ad (t

m2)


Correlation r2 =

Var actual rock load versus calculated rock load

95 confidence

Figure 12 Correlation between estimated rock loads for 48m widegalleries

0717

20 22 24 26 28 30 32 34 36 38 40242628303234363840

Calc

ulat

ed ro

ck lo

ad (t

m2)


Actual rock load versus calculated rock load (junctions)Correlation r2 =

95 confidence

Figure 13 Correlation between estimated rock loads for 48m widegalleries and junctions

00

10

20

30

40

50

60

70

000 2000 4000 6000 8000(RMR)

RMR versus rock load

Transition line

36m gallery width42m gallery width48m gallery width

Rock

load

(tm

2)

Figure 14 Plot between assumed RMR and rock load for 36 42and 48m galleries

Journal of Mining 9

00102030405060708090

0 10 20 30 40 50 60 70 80

Transition line


(RMR)


Rock

load

(tm

2)

Figure 15 Plot between assumed RMR and rock load for 36 42and 48m junctions

Conflict of Interests

The authors declare that they do not have conflict of interestsregarding of the publication of this paper

Acknowledgments

The authors would like to thank the Director of CIMFRDhanbad and Director of ISM Dhanbad and also the MineManagement for their kind support during the researchwork The authors are also thankful to Mr S K Singh SeniorPrincipal Scientist and Head Geo-mechanical Lab CIMFRDhanbad for his sincere help during testing of rock samplesThe work forms a part of the PhD work of the first authorbeing carried out at ISM Dhanbad Jharkhand India

References

[1] A K Sinha B Bhattacharjee and R Sharma ldquoRole of resinbolting in strata management in Indian coal minesmdasha synopticoverviewrdquo in Proceedings of the National Seminar on Geome-chanics and Ground Control pp 3ndash15 2003

[2] M Murkute A K Sinha and V M S R Murthy ldquoA review ofrock mass classification system for support design in n coalmine development roadwaysmdasha strategy for improvementrdquo inProceedings of the Seminar on 1st Indian Mineral Congress pp56ndash65 2005

[3] B C Sarkar B N Mahanta K Saikia P R Paul and G SinghldquoGeo-environmental quality assessment in Jharia coalfieldIndia using multivariate statistics and geographic informationsystemrdquo Environmental Geology vol 51 no 7 pp 1177ndash11962007

[4] CMRI Report ldquoGeomechanical classification of roof rocks vis-a-vis roof supportsrdquo SandT Project Report 1987

[5] V Venkateswarlu A K Ghose and N M Raju ldquoRock-massclassification for design of roof supportsmdasha statistical evalua-tion of parametersrdquo Mining Science and Technology vol 8 no2 pp 97ndash107 1989

[6] Z T Bieniawski Rock Mechanics Design in Mining and Tunnel-ing Balkema Cape Town South Africa 1984

[7] Z T Bieniawski ldquoRock mass classification as a design aid intunnellingrdquo Tunnels and Tunnelling International vol 20 no 7pp 19ndash22 1988

[8] A K Singh A Sinha A Paul and K Saikia ldquoGeotechnicalinvestigation for support design in depillaring panels in Indiancoalminesrdquo Journal of Scientific and Industrial Research vol 64no 5 pp 358ndash363 2005

[9] A Paul A K Singh N Kumar and D G Rao ldquoEmpiricalapproach for estimation of rock load in development workingsof room and pillar miningrdquo Journal of Scientific and IndustrialResearch vol 68 no 3 pp 214ndash216 2009

[10] Bureau of Indian Standard Indian standard 100501981[11] Bureau of Indian Standard Indian standard 91431979

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2 Journal of Mining

0 312

(km)

Jharia Coalfield

New Delhi

JharkhandMumbai

Chennai

Son River

DaltonganjBarwadih

Lohardaga

GayaGT Road

Hazaribag

Ranchi

Damodar River

MuriPurulia

Gomoh

AdraDamodar River

Barakar River

GT Road

Asansol

Dhanbad

JhariaCoalfield

Up Bihar

JharkhandMP Jharia

BengalW

N

Orissa

(1)(2)

(3)(4)

(5)

(6)

0 16 48

(km)

28∘

Kolkata

(1) Raniganj(2) Jharia(3) Bokaro(4) North Karanpura(5) Daltonganj

(6) RamgarhRail lineRoadRiver

84∘0998400

85∘0998400

86∘0998400

87∘0998400

84∘0998400

24∘0998400 24

∘0998400

85∘0998400

86∘0998400

87∘0998400

Figure 1 Location of Jharia coalfield in India

Table 1 Parameters of CMRI-ISM rock mass rating

Parameter Maximum ratingLayer thickness (cm) 30Structural features 25Weatherability (1st cycle slake durability index) 20Compressive strength (Kgcm2) 15Groundwater condition (mLmin) 10

of coal roof there are different small bands or layers of coalwhich are measured as layer thickness

Structural features are geological structures which causeroof deterioration and constitute major faults slips jointsand other sedimentary features like sandstone channel plantimpression and so forthWater percolation is themajor prob-lem in Indian coal mines thus weatherability is importantbecause many coal measure rocks become weak or disinte-grate due to weathering especially in presence of water Themeasure for this parameter is the 1st cycle slake durabilityindex (SDI) determined by slake durability apparatus [10]

Compressive strength of rock is determined in the laboratoryas per Bureau of Indian Standards [11]

Groundwater seepage is measured by drilling a 15 to18m long hole in roof and thereafter collecting the waterpercolation through it The rate of percolation is expressedin mLmin

Adjustments for depth lateral stress induced stressesmethod of excavation and gallery span aremade for account-ing their positive neutral and negative contribution to RMRvalues as given in Table 2

After due adjustment adjusted RMR is used for estima-tion of rock load in galleries and junctions from the followingequations

Rock load in roadways (tm2)

= 119861 sdot 119863 sdot (17 minus 0037RMR + 00002RMR2) (1)

Rock load in junctions (tm2) = 5 sdot 11986103 sdot 119863(1 minus RMR100)2

(2)

Journal of Mining 3



AdjustedRMR






Up to 30reduction

RMR times (07to 08)


Up to 30reduction

RMR times (07to 08)




RMR times (08to 09)






55 56 57 58 59 60 61 62RMR

15

16

17

18

19

20

21

95 confidence

Rock

load

(tm

2)


Correlation r2 = 09

0

4

4 lowast RMR


30 35 40 45 50 55 60 65RMR

14161820222426283032343638

95 confidence

Rock

load

(tm

2)










4 Journal of Mining














Journal of Mining 5




Gallery(tm2)

Junction(tm2)

Gallery(tm2)

Junction(tm2)


15 25 18 2715 26 17 2620 31 22 3118 28 17 26


18 27 18 2619 28 19 2815 24 16 2518 27 18 2622 30 21 2914 21 18 2718 28 18 2634 42 33 4029 36 30 3734 41 34 4129 36 31 3831 38 30 3833 40 35 4130 37 31 3829 36 30 3731 39 30 3835 43 34 4130 37 31 3829 36 29 3732 35 31 36


32 36 33 3732 36 34 3833 38 33 3715 22 19 2728 36 23 2924 30 22 2917 24 18 26



40 42 44 46 48 50 52 54 56 58 60 62 64141618202224262830323436

RMR

95 confidence

Rock

load

(tm

2)





094

55 56 57 58 59 60 61 62252627282930313233

RMR

Rock

load

(tm

2)


Correlation r2 =

95 confidence









6 Journal of Mining















(junctions) 675 226 20 8 005



(junctions) 510 81 74 40 0000000



(junctions) 513 32 148 14 0000000

30 35 40 45 50 55 60 6520242832364044

RMR

Rock

load

(tm

2)


096Correlation r2 =

95 confidence

00602 lowast RMR




119905 =( 119879minus 119862)

radicVar119879119899119879+ Var119862119899119862

(3)




Journal of Mining 7

0717

40 42 44 46 48 50 52 54 56 58 60 62 642022242628303234363840

RMR

95 confidence

Rock

load

(tm

2)





8 Conclusion





1198772 = 094



1198772 = 098



1198772 = 086

15 16 17 18 19 20 211718192021222324

95 confidence

Calc

ulat

ed ro

cklo

ad (t

m2)





25 26 27 28 29 30 31 32 33252627282930313233

Calc

ulat

ed ro

cklo

ad (t

m2)



95 confidence




1198772 = 095



1198772 = 096



1198772 = 072(4)




8 Journal of Mining

14 16 18 20 22 24 26 28 30 32 34 36 382022242628303234363840424446

Calc

ulat

ed ro

ck lo

ad (t

m2)




95 confidence


20 22 24 26 28 30 32 34 36 38 40 42 44 462426283032343638404244

95 confidence

Calc

ulat

ed ro

ck lo

ad (t

m2)






Abbreviations




14 16 18 20 22 24 26 28 30 32 34 361618202224262830323436

Calc

ulat

ed ro

ck lo

ad (t

m2)


Correlation r2 =


95 confidence


0717

20 22 24 26 28 30 32 34 36 38 40242628303234363840

Calc

ulat

ed ro

ck lo

ad (t

m2)



95 confidence


00

10

20

30

40

50

60

70

000 2000 4000 6000 8000(RMR)


Transition line


Rock

load

(tm

2)


Journal of Mining 9

00102030405060708090

0 10 20 30 40 50 60 70 80

Transition line


(RMR)


Rock

load

(tm

2)




Acknowledgments


References




















Volume 2014

Mining


Journal of



Geophysics







Journal of




Advances in











Geology Advances in

Journal of Mining 3



AdjustedRMR






Up to 30reduction

RMR times (07to 08)


Up to 30reduction

RMR times (07to 08)




RMR times (08to 09)






55 56 57 58 59 60 61 62RMR

15

16

17

18

19

20

21

95 confidence

Rock

load

(tm

2)


Correlation r2 = 09

0

4

4 lowast RMR


30 35 40 45 50 55 60 65RMR

14161820222426283032343638

95 confidence

Rock

load

(tm

2)










4 Journal of Mining














Journal of Mining 5




Gallery(tm2)

Junction(tm2)

Gallery(tm2)

Junction(tm2)


15 25 18 2715 26 17 2620 31 22 3118 28 17 26


18 27 18 2619 28 19 2815 24 16 2518 27 18 2622 30 21 2914 21 18 2718 28 18 2634 42 33 4029 36 30 3734 41 34 4129 36 31 3831 38 30 3833 40 35 4130 37 31 3829 36 30 3731 39 30 3835 43 34 4130 37 31 3829 36 29 3732 35 31 36


32 36 33 3732 36 34 3833 38 33 3715 22 19 2728 36 23 2924 30 22 2917 24 18 26



40 42 44 46 48 50 52 54 56 58 60 62 64141618202224262830323436

RMR

95 confidence

Rock

load

(tm

2)





094

55 56 57 58 59 60 61 62252627282930313233

RMR

Rock

load

(tm

2)


Correlation r2 =

95 confidence









6 Journal of Mining















(junctions) 675 226 20 8 005



(junctions) 510 81 74 40 0000000



(junctions) 513 32 148 14 0000000

30 35 40 45 50 55 60 6520242832364044

RMR

Rock

load

(tm

2)


096Correlation r2 =

95 confidence

00602 lowast RMR




119905 =( 119879minus 119862)

radicVar119879119899119879+ Var119862119899119862

(3)




Journal of Mining 7

0717

40 42 44 46 48 50 52 54 56 58 60 62 642022242628303234363840

RMR

95 confidence

Rock

load

(tm

2)





8 Conclusion





1198772 = 094



1198772 = 098



1198772 = 086

15 16 17 18 19 20 211718192021222324

95 confidence

Calc

ulat

ed ro

cklo

ad (t

m2)





25 26 27 28 29 30 31 32 33252627282930313233

Calc

ulat

ed ro

cklo

ad (t

m2)



95 confidence




1198772 = 095



1198772 = 096



1198772 = 072(4)




8 Journal of Mining

14 16 18 20 22 24 26 28 30 32 34 36 382022242628303234363840424446

Calc

ulat

ed ro

ck lo

ad (t

m2)




95 confidence


20 22 24 26 28 30 32 34 36 38 40 42 44 462426283032343638404244

95 confidence

Calc

ulat

ed ro

ck lo

ad (t

m2)






Abbreviations




14 16 18 20 22 24 26 28 30 32 34 361618202224262830323436

Calc

ulat

ed ro

ck lo

ad (t

m2)


Correlation r2 =


95 confidence


0717

20 22 24 26 28 30 32 34 36 38 40242628303234363840

Calc

ulat

ed ro

ck lo

ad (t

m2)



95 confidence


00

10

20

30

40

50

60

70

000 2000 4000 6000 8000(RMR)


Transition line


Rock

load

(tm

2)


Journal of Mining 9

00102030405060708090

0 10 20 30 40 50 60 70 80

Transition line


(RMR)


Rock

load

(tm

2)




Acknowledgments


References




















Volume 2014

Mining


Journal of



Geophysics







Journal of




Advances in











Geology Advances in

4 Journal of Mining














Journal of Mining 5




Gallery(tm2)

Junction(tm2)

Gallery(tm2)

Junction(tm2)


15 25 18 2715 26 17 2620 31 22 3118 28 17 26


18 27 18 2619 28 19 2815 24 16 2518 27 18 2622 30 21 2914 21 18 2718 28 18 2634 42 33 4029 36 30 3734 41 34 4129 36 31 3831 38 30 3833 40 35 4130 37 31 3829 36 30 3731 39 30 3835 43 34 4130 37 31 3829 36 29 3732 35 31 36


32 36 33 3732 36 34 3833 38 33 3715 22 19 2728 36 23 2924 30 22 2917 24 18 26



40 42 44 46 48 50 52 54 56 58 60 62 64141618202224262830323436

RMR

95 confidence

Rock

load

(tm

2)





094

55 56 57 58 59 60 61 62252627282930313233

RMR

Rock

load

(tm

2)


Correlation r2 =

95 confidence









6 Journal of Mining















(junctions) 675 226 20 8 005



(junctions) 510 81 74 40 0000000



(junctions) 513 32 148 14 0000000

30 35 40 45 50 55 60 6520242832364044

RMR

Rock

load

(tm

2)


096Correlation r2 =

95 confidence

00602 lowast RMR




119905 =( 119879minus 119862)

radicVar119879119899119879+ Var119862119899119862

(3)




Journal of Mining 7

0717

40 42 44 46 48 50 52 54 56 58 60 62 642022242628303234363840

RMR

95 confidence

Rock

load

(tm

2)





8 Conclusion





1198772 = 094



1198772 = 098



1198772 = 086

15 16 17 18 19 20 211718192021222324

95 confidence

Calc

ulat

ed ro

cklo

ad (t

m2)





25 26 27 28 29 30 31 32 33252627282930313233

Calc

ulat

ed ro

cklo

ad (t

m2)



95 confidence




1198772 = 095



1198772 = 096



1198772 = 072(4)




8 Journal of Mining

14 16 18 20 22 24 26 28 30 32 34 36 382022242628303234363840424446

Calc

ulat

ed ro

ck lo

ad (t

m2)




95 confidence


20 22 24 26 28 30 32 34 36 38 40 42 44 462426283032343638404244

95 confidence

Calc

ulat

ed ro

ck lo

ad (t

m2)






Abbreviations




14 16 18 20 22 24 26 28 30 32 34 361618202224262830323436

Calc

ulat

ed ro

ck lo

ad (t

m2)


Correlation r2 =


95 confidence


0717

20 22 24 26 28 30 32 34 36 38 40242628303234363840

Calc

ulat

ed ro

ck lo

ad (t

m2)



95 confidence


00

10

20

30

40

50

60

70

000 2000 4000 6000 8000(RMR)


Transition line


Rock

load

(tm

2)


Journal of Mining 9

00102030405060708090

0 10 20 30 40 50 60 70 80

Transition line


(RMR)


Rock

load

(tm

2)




Acknowledgments


References




















Volume 2014

Mining


Journal of



Geophysics







Journal of




Advances in











Geology Advances in

Journal of Mining 5




Gallery(tm2)

Junction(tm2)

Gallery(tm2)

Junction(tm2)


15 25 18 2715 26 17 2620 31 22 3118 28 17 26


18 27 18 2619 28 19 2815 24 16 2518 27 18 2622 30 21 2914 21 18 2718 28 18 2634 42 33 4029 36 30 3734 41 34 4129 36 31 3831 38 30 3833 40 35 4130 37 31 3829 36 30 3731 39 30 3835 43 34 4130 37 31 3829 36 29 3732 35 31 36


32 36 33 3732 36 34 3833 38 33 3715 22 19 2728 36 23 2924 30 22 2917 24 18 26



40 42 44 46 48 50 52 54 56 58 60 62 64141618202224262830323436

RMR

95 confidence

Rock

load

(tm

2)





094

55 56 57 58 59 60 61 62252627282930313233

RMR

Rock

load

(tm

2)


Correlation r2 =

95 confidence









6 Journal of Mining















(junctions) 675 226 20 8 005



(junctions) 510 81 74 40 0000000



(junctions) 513 32 148 14 0000000

30 35 40 45 50 55 60 6520242832364044

RMR

Rock

load

(tm

2)


096Correlation r2 =

95 confidence

00602 lowast RMR




119905 =( 119879minus 119862)

radicVar119879119899119879+ Var119862119899119862

(3)




Journal of Mining 7

0717

40 42 44 46 48 50 52 54 56 58 60 62 642022242628303234363840

RMR

95 confidence

Rock

load

(tm

2)





8 Conclusion





1198772 = 094



1198772 = 098



1198772 = 086

15 16 17 18 19 20 211718192021222324

95 confidence

Calc

ulat

ed ro

cklo

ad (t

m2)





25 26 27 28 29 30 31 32 33252627282930313233

Calc

ulat

ed ro

cklo

ad (t

m2)



95 confidence




1198772 = 095



1198772 = 096



1198772 = 072(4)




8 Journal of Mining

14 16 18 20 22 24 26 28 30 32 34 36 382022242628303234363840424446

Calc

ulat

ed ro

ck lo

ad (t

m2)




95 confidence


20 22 24 26 28 30 32 34 36 38 40 42 44 462426283032343638404244

95 confidence

Calc

ulat

ed ro

ck lo

ad (t

m2)






Abbreviations




14 16 18 20 22 24 26 28 30 32 34 361618202224262830323436

Calc

ulat

ed ro

ck lo

ad (t

m2)


Correlation r2 =


95 confidence


0717

20 22 24 26 28 30 32 34 36 38 40242628303234363840

Calc

ulat

ed ro

ck lo

ad (t

m2)



95 confidence


00

10

20

30

40

50

60

70

000 2000 4000 6000 8000(RMR)


Transition line


Rock

load

(tm

2)


Journal of Mining 9

00102030405060708090

0 10 20 30 40 50 60 70 80

Transition line


(RMR)


Rock

load

(tm

2)




Acknowledgments


References




















Volume 2014

Mining


Journal of



Geophysics







Journal of




Advances in











Geology Advances in

6 Journal of Mining















(junctions) 675 226 20 8 005



(junctions) 510 81 74 40 0000000



(junctions) 513 32 148 14 0000000

30 35 40 45 50 55 60 6520242832364044

RMR

Rock

load

(tm

2)


096Correlation r2 =

95 confidence

00602 lowast RMR




119905 =( 119879minus 119862)

radicVar119879119899119879+ Var119862119899119862

(3)




Journal of Mining 7

0717

40 42 44 46 48 50 52 54 56 58 60 62 642022242628303234363840

RMR

95 confidence

Rock

load

(tm

2)





8 Conclusion





1198772 = 094



1198772 = 098



1198772 = 086

15 16 17 18 19 20 211718192021222324

95 confidence

Calc

ulat

ed ro

cklo

ad (t

m2)





25 26 27 28 29 30 31 32 33252627282930313233

Calc

ulat

ed ro

cklo

ad (t

m2)



95 confidence




1198772 = 095



1198772 = 096



1198772 = 072(4)




8 Journal of Mining

14 16 18 20 22 24 26 28 30 32 34 36 382022242628303234363840424446

Calc

ulat

ed ro

ck lo

ad (t

m2)




95 confidence


20 22 24 26 28 30 32 34 36 38 40 42 44 462426283032343638404244

95 confidence

Calc

ulat

ed ro

ck lo

ad (t

m2)






Abbreviations




14 16 18 20 22 24 26 28 30 32 34 361618202224262830323436

Calc

ulat

ed ro

ck lo

ad (t

m2)


Correlation r2 =


95 confidence


0717

20 22 24 26 28 30 32 34 36 38 40242628303234363840

Calc

ulat

ed ro

ck lo

ad (t

m2)



95 confidence


00

10

20

30

40

50

60

70

000 2000 4000 6000 8000(RMR)


Transition line


Rock

load

(tm

2)


Journal of Mining 9

00102030405060708090

0 10 20 30 40 50 60 70 80

Transition line


(RMR)


Rock

load

(tm

2)




Acknowledgments


References




















Volume 2014

Mining


Journal of



Geophysics







Journal of




Advances in











Geology Advances in

Journal of Mining 7

0717

40 42 44 46 48 50 52 54 56 58 60 62 642022242628303234363840

RMR

95 confidence

Rock

load

(tm

2)





8 Conclusion





1198772 = 094



1198772 = 098



1198772 = 086

15 16 17 18 19 20 211718192021222324

95 confidence

Calc

ulat

ed ro

cklo

ad (t

m2)





25 26 27 28 29 30 31 32 33252627282930313233

Calc

ulat

ed ro

cklo

ad (t

m2)



95 confidence




1198772 = 095



1198772 = 096



1198772 = 072(4)




8 Journal of Mining

14 16 18 20 22 24 26 28 30 32 34 36 382022242628303234363840424446

Calc

ulat

ed ro

ck lo

ad (t

m2)




95 confidence


20 22 24 26 28 30 32 34 36 38 40 42 44 462426283032343638404244

95 confidence

Calc

ulat

ed ro

ck lo

ad (t

m2)






Abbreviations




14 16 18 20 22 24 26 28 30 32 34 361618202224262830323436

Calc

ulat

ed ro

ck lo

ad (t

m2)


Correlation r2 =


95 confidence


0717

20 22 24 26 28 30 32 34 36 38 40242628303234363840

Calc

ulat

ed ro

ck lo

ad (t

m2)



95 confidence


00

10

20

30

40

50

60

70

000 2000 4000 6000 8000(RMR)


Transition line


Rock

load

(tm

2)


Journal of Mining 9

00102030405060708090

0 10 20 30 40 50 60 70 80

Transition line


(RMR)


Rock

load

(tm

2)




Acknowledgments


References




















Volume 2014

Mining


Journal of



Geophysics







Journal of




Advances in











Geology Advances in

8 Journal of Mining

14 16 18 20 22 24 26 28 30 32 34 36 382022242628303234363840424446

Calc

ulat

ed ro

ck lo

ad (t

m2)




95 confidence


20 22 24 26 28 30 32 34 36 38 40 42 44 462426283032343638404244

95 confidence

Calc

ulat

ed ro

ck lo

ad (t

m2)






Abbreviations




14 16 18 20 22 24 26 28 30 32 34 361618202224262830323436

Calc

ulat

ed ro

ck lo

ad (t

m2)


Correlation r2 =


95 confidence


0717

20 22 24 26 28 30 32 34 36 38 40242628303234363840

Calc

ulat

ed ro

ck lo

ad (t

m2)



95 confidence


00

10

20

30

40

50

60

70

000 2000 4000 6000 8000(RMR)


Transition line


Rock

load

(tm

2)


Journal of Mining 9

00102030405060708090

0 10 20 30 40 50 60 70 80

Transition line


(RMR)


Rock

load

(tm

2)




Acknowledgments


References




















Volume 2014

Mining


Journal of



Geophysics







Journal of




Advances in











Geology Advances in

Journal of Mining 9

00102030405060708090

0 10 20 30 40 50 60 70 80

Transition line


(RMR)


Rock

load

(tm

2)




Acknowledgments


References




















Volume 2014

Mining


Journal of



Geophysics







Journal of




Advances in











Geology Advances in










Volume 2014

Mining


Journal of



Geophysics







Journal of




Advances in











Geology Advances in

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