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इंटरनेट मानक Disclosure to Promote the Right To Information Whereas the Parliament of India has set out to provide a practical regime of right to information for citizens to secure access to information under the control of public authorities, in order to promote transparency and accountability in the working of every public authority, and whereas the attached publication of the Bureau of Indian Standards is of particular interest to the public, particularly disadvantaged communities and those engaged in the pursuit of education and knowledge, the attached public safety standard is made available to promote the timely dissemination of this information in an accurate manner to the public. “जान1 का अ+धकार, जी1 का अ+धकार” “प0रा1 को छोड न’ 5 तरफ” Mazdoor Kisan Shakti Sangathan Jawaharlal Nehru “The Right to Information, The Right to Live” “Step Out From the Old to the New” IS 8764 (1998): Method of determination of point load strength index of rocks [CED 48: Rock Mechanics] “!ान $ एक न’ भारत का +नम-ण” Satyanarayan Gangaram Pitroda ““IInnvveenntt aa NNeeww IInnddiiaa UUssiinngg KKnnoowwlleeddggee”” “!ान एक ऐसा खजाना > जो कभी च0राया नहB जा सकता हहहहै””ै” Bhartṛhari—Nītiśatakam “Knowledge is such a treasure which cannot be stolen” IS 8764 : 1998 REAFFIRMED 2008 ~rtr~ g;rftwr ) ( qe;HI Indian Standard METHOD FOR DETERMINATION OF POINT LOAD STRENGTH INDEX OF ROCKS ( First Revision) ICS 19.060;91.100.20 1998 BUREAU OF INDIAN STANDARDS MANAK BHAVAN, 9 BAHADUR SHAH ZAFAR MARG NEW DEL HI 110002 September 1998 PriceGroup 5 AMENDMENT NO. 1 DECEMBER 2006 TO IS 8764 : 1998METHOD FORDETERMINATION OF POINTLOAD STRENGTH INDEX OFROCKS (FarsiRnisioll) (Page6,clause7.1.1)- Substitutethefollowingfortheexistingformula: p I, (SO) = where 1.(50)=pointloadstrengthindexinMPa(forthestandardcoresize), P =failureloadinN, D =corediameterinnun,and Dso =standardcorediameter(50mm). (Page6,clause7.3)- Substitutethefollowingfortheexistingformula: P IL (SO) == ---- (Dr¥)°·7S ~D so where P =peakloadinNatfailure, (DW) =theminimumcrosssectionalareapassingthroughpointloadsin mm2 , I (SO)=pointloadlumpsttengthindexinMPa, L Dso =standardsizeoflump(SO nun), D =distancebetweenpointloadsinmm,and W =averagewidthofminimumcrosssectionalareainmm. (Page 6, clause7.4, lastline)- Delete 'This ---only' and insertthe followingNote: NOTE- Thecorrelationsin7.2and7.4areapproximateforthepurposeofcluaificatian of rockmu..andvalidformainlyunweath«edandilOtrOpicrocks. (CED48) Reprolf&PhyUnit,BIS.NewDelhi,India (cid:65)(cid:77)(cid:69)(cid:78)(cid:68)(cid:77)(cid:69)(cid:78)(cid:84)(cid:32)(cid:78)(cid:79)(cid:46)(cid:32)(cid:50) (cid:79)(cid:67)(cid:84)(cid:79)(cid:66)(cid:69)(cid:82)(cid:32)(cid:32)(cid:50)(cid:48)(cid:49)(cid:49) (cid:84)(cid:79) (cid:73)(cid:83)(cid:32)(cid:56)(cid:55)(cid:54)(cid:52)(cid:32)(cid:58)(cid:32)(cid:49)(cid:57)(cid:57)(cid:56)(cid:32)(cid:77)(cid:69)(cid:84)(cid:72)(cid:79)(cid:68)(cid:32)(cid:70)(cid:79)(cid:82)(cid:32)(cid:68)(cid:69)(cid:84)(cid:69)(cid:82)(cid:77)(cid:73)(cid:78)(cid:65)(cid:84)(cid:73)(cid:79)(cid:78)(cid:32)(cid:79)(cid:70)(cid:32)(cid:80)(cid:79)(cid:73)(cid:78)(cid:84)(cid:32)(cid:76)(cid:79)(cid:65)(cid:68) (cid:83)(cid:84)(cid:82)(cid:69)(cid:78)(cid:71)(cid:84)(cid:72)(cid:32)(cid:73)(cid:78)(cid:68)(cid:69)(cid:88)(cid:32)(cid:79)(cid:70)(cid:32)(cid:82)(cid:79)(cid:67)(cid:75)(cid:83) (cid:40)(cid:70)(cid:105)(cid:114)(cid:115)(cid:116)(cid:32)(cid:82)(cid:101)(cid:118)(cid:105)(cid:115)(cid:105)(cid:111)(cid:110)(cid:41) (cid:40)(cid:80)(cid:97)(cid:103)(cid:101)(cid:32)(cid:53)(cid:44)(cid:99)(cid:108)(cid:97)(cid:117)(cid:115)(cid:101)(cid:54)(cid:46)(cid:52)(cid:46)(cid:49)(cid:44)(cid:108)(cid:105)(cid:110)(cid:101)(cid:32)(cid:50)(cid:41)(cid:8212)(cid:32)(cid:83)(cid:117)(cid:98)(cid:115)(cid:116)(cid:105)(cid:116)(cid:117)(cid:116)(cid:101)(cid:32)(cid:8216)(cid:49)(cid:46)(cid:48)(cid:8217)(cid:102)(cid:111)(cid:114)(cid:32)(cid:8216)(cid:49)(cid:46)(cid:53)(cid:8217)(cid:46) (cid:40)(cid:80)(cid:97)(cid:103)(cid:101)(cid:32)(cid:53)(cid:44)(cid:99)(cid:108)(cid:97)(cid:117)(cid:115)(cid:101)(cid:54)(cid:46)(cid:52)(cid:46)(cid:51)(cid:44)(cid:32)(cid:108)(cid:105)(cid:110)(cid:101)(cid:52)(cid:41)(cid:8212)(cid:32)(cid:83)(cid:117)(cid:98)(cid:115)(cid:116)(cid:105)(cid:116)(cid:117)(cid:116)(cid:101)(cid:32)(cid:8216)(cid:48)(cid:46)(cid:53)(cid:48)(cid:8217)(cid:102)(cid:111)(cid:114)(cid:32)(cid:8216)(cid:48)(cid:46)(cid:55)(cid:53)(cid:8217)(cid:46) (cid:40)(cid:67)(cid:69)(cid:68)(cid:32)(cid:52)(cid:56)(cid:41) (cid:82)(cid:101)(cid:112)(cid:114)(cid:111)(cid:103)(cid:114)(cid:97)(cid:112)(cid:104)(cid:121)(cid:32)(cid:85)(cid:110)(cid:105)(cid:116)(cid:44)(cid:32)(cid:66)(cid:73)(cid:83)(cid:44)(cid:32)(cid:78)(cid:101)(cid:119)(cid:32)(cid:68)(cid:101)(cid:108)(cid:104)(cid:105)(cid:44)(cid:32)(cid:73)(cid:110)(cid:100)(cid:105)(cid:97) RockMechanics Sectional Committee,CED48 I:()REWORD This Indian Standard (FirstRevision) wasadoptedbytheBureauofIndian Standards, after thedraft finalized hythe RockMechanicsSectionalCommitteehadbeenapproved bytheCivilEngineering DivisionCouncil. The point loadtest isprimarily anindextestfor strengthclassificationofrock materials. Although itmay be used in the laboratory, itis mainly intended forfield measurements on rock core and lump specimens. The results ofthe test should be used to predict the uniaxial compressive strength of unweathered rock for the purposeofRockMassClassification. Theapparatususedinthetestislightandportableandcanbeusedinthe laboratory aswellasinthefield. When first introduced, the point loadstrength test was used mainly topredict uniaxial compressive strength which was then the established test forgeneral purpose rockstrengthclassification. Point load strength now often replaces uniaxialcompressive strength inthisrole,since(whenproperly conducted) itisasreliable and much quicker to measure. It should be useddirectly for rockclassification. since correlations with uniaxial compressive strength are only approximate. On average, uniaxial compressive strength is20-25 times point loadstrength indexof rockcores. However, intestson many different rocktypes, theratiocan varybetween 15and50especially foranisotropicrocks,sothaterrorsof upto 100percentarepossibleinusinganarbitrary ratio value to predict compressivestrength frompointloadstrength. The point loadstrength test isaform of 'indirect tensile' test, but this is largely irrelevant to its primary role in rock classification and strength characterization. Is(50) isapproximately0.80timestheuniaxialtensileorBraziliantensilestrength. This standard is revision andsynthesis of twoold standard on point load strength index and point load lump strength index. Revision isneededbecauseofadvancesintheinterpretationsofthetestdata anddevelopment of new correlations for estimating uniaxial compressive strength of rock material. This standard includes diametricaltest fordeterminingpointstrength index,axial testand lurnptestfordeterminingpoint loadlump strengthindex. Thestandardsizeofrockcoresandlumpsiscommon,thatis,50mm. Thesizecorrelationchart isnotincluded asitisaccounted forincalculationofindicesstrengthanisotropyindex isintroduced totestthe anisotropic andlaminatedrockmaterials. In the formulation of this standard due weightage has been given to international co-ordination among the standards and practices prevailing indifferentcountries inadditiontorelating ittothepractices inthe fieldin thiscountry. IS 10785: 1983 'Method fordetermination of compressive and tensile strength for point load tests on rock IUlllPS' hasbeen withdrawnanditsprovisionshavebeenincludedinthisrevision. Technical CommitteeresponsiblefortheformulationofthisstandardisgivenatAnnexA. In reporting the result of a test or analysis in accordance with this standard. if the final value, observed or calculated, istoberoundedoff.itshallbedoneinaccordancewithIS2:1960'Rules forroundingoffnumerical values(revised)'. IS8764: 1998 Indian Standard METHOD FOR DETERMINATION OF POINT LOAD STRENGTH INDEX OF ROCKS ( First Revision) 1 SCOPE materialssuchastungstencarbideorhardenedsteelso thattheyremainundamagedduringfrequenttesting. 1.1 This standard lays down the procedurefor determination of diametral and axial point load 4.1.3 This frameshallhaveadequateadjustmentto strengthindexof rock cores, cut blocksor irregular alignperfectlythe loadingaxis passingthrough the lumps,whichmaybetestedwithoutanytreatment. centreofthebearingplatesandloadingplatensatall thepositionsoftheramofthehydraulicjack. 1.2 The testing may be carried out either in the laboratoryorinfieldatthedrillingsite. 4.1.4 ThediaphragmboltshowninFig.2shouldbe usedtocheckthealignmentoftheloadingaxis. 1.3 Thesetestsarenotreliableifpointloadstrength index(IsorIL)islessthan1MPa. 4.1.5 Thepointloadtestershallbeportable. 1 REFERENCES 4.1 HydraulicJackand Accessories TheIndianStandardsgivenbelowcontainprovisions 4.2.1 The loadingcapacityofhydraulicjack should which through reference in this text, constitute be of sufficient capacity to break the largest and provisionofthisstandard. Atthetimeofpublication, strongestspecimentobetested. the editions indicatedwerevalid. All standardsare 4.2.1 Thereshallnotbeanyplaybetweentheramand subjecttorevision,andpartiestoagreementsbasedon thejack. this standard are encouraged to investigate the possibilityofapplyingthemostrecenteditionsofthe 4.2.3 The ram shall have low friction seals. The standardsindicatedbelow: frictionbetweentheramandthejackshallbelessthan SON(5kgt). ISNo. Title 4.2.4 TIlesystemistoberesistanttohydraulicshock 11358: 1987 Glossary of terms and symbols and vibration so that accuracy of readings is not applicabletorockmechanics adverselyaffectedbyrepeatedtesting. 13030: 1991 Methodoftestforlaboratorydeter minationofwatercontent,porosity, -42.~ If quick-retractingram is used to reduce the density and related properties of delaybetweentests,eithertheramreturnspringforce rockmaterial and ram friction should togetherbelessthanabout 5percentofthesmallestloadtobemeasuredduring 3 TERMINOLOGY testing,oranindependentloadcellratherthananoil Forthepurposeofthisstandard,thedefinitionofterms pressuregaugeshouldbeusedforloaddetermination. giveninIS 11358shallapply. These forcecan besignificantwhentesting weaker andsmallerspecimens. 4 APPARATUS 4.3 PressureGauges Figures 1 and 2 show a typical design. However alternativesuitabledesignmayalsobeused. 4.3.1 Bourden type pressure gauges of 200 mm diameter shall be equipped with maximumreading 4.1 LoadingFrame indicator. 4.1.1 The frame shallbe sufficientlyrigidandshall 4.3.2 The gauges shall be fitted with a hydraulic besodesignedthattheloadapplicationisinplumb. 'snubber' oforificetypetoprotectthegaugesagainst 4.1.2 The distance between the topand the bottom suddendecompression. bearing plates of this frame shall accommodate a 4.3.3 Thesegaugesshallhavethefollowingranges: hydraulic jack, two loading platens and platen to platenclearancefortestingof rockspecimensi nthe a) GaugeNo.1- Maximumloadingcapacityof rangeof 15...100nun. Theplatens shouldbeofhard 25kN(2.500kgt)toreadupto0.25kN(25kgt). IS8764:1998 .,.2SmmHOLE FOR FIXING VERTICAL SUPPORT HOLE TO TIGHTEN THE PLATEN i -1,0 ~-----4S0 LOADtNG PLATEN ANGL.E 40.40xSm", LOADING SET-UP Alldimensionsinmillimetrcs. FIG. 1 ATYPICALILLUSTRATIONOPPoINTLoADTESTINGSYSTEMANDLoADINGPLATEN b) GaugeNo.2- Maximumloadingcapacityof -,..------1t'--4'2mmHOLE 100kN(10000kgf)toreadupto0.50leN(SO kgt). 6c! Thegaugesshallhaveanaccuracyof±2percent. COLLAR 4.3.4 The gaugesshallbefitted withquickrelease couplingsforinterchanging themtosuitthestrength ofacoreorblockandshalJbeprovidedwithautomatic 10mm cut-offvalvetoisolatethelowercapacitygausewhen mIn. TOP CENTRENUT ~6 itslimitisexceeded. ~nUN CROSS-WIRES , 4.3.5 A calibration chartshallbe prepared foreach gaugewiththehelpofaprovingring. 4.3.6 Loadsof upto 50leN arecommonly required for the largerhardrockspecimens. The maximum specimensizethatcanbetestedbyagivenmachineis Alldimensionsinmillimetres. determined by the machine's load and distance FlO. 2 DIAPHRAGM BOLTFORCHECKING measuring sensitivity. Tests on specimeils smaller ALIGNMENTOPBOTrOMPLATEN = thanD 25 mm require particular precautions to 2 IS8764:1998 ensurethatthemeasuringsensitivityissufficient.The in contact, and should preferably include a zero ruseofrequiredtestloadshouldbeestimatedbefore adjustment. testing,fromapproximateassumedstrengthvalues,to 4.4.4 If significant platen penetration occurs, the ensure that the load capacity and sensitivity of the dimension D to be used in calculating point load equipment are adequate. It may be necessary to strengthshouldbethevalueDmeasuredattheinstant changetheloadmeasuringgaugeorloadcell,ortotest of failure. Theerror in assumingD to be its initial smaller or larger specimens to conform with the value is negligible when the specimen is large or capacityofavailableequipmentorwiththeaccuracy strong. The failurevaluemay always beused as an specificationsforthistest. alternativetotheinitialvalueand ispreferred ifthe 4.4 DIstanceMeasuringSystem equipmentallowsittobemeasured. Measurementof W or D made perpendicularto the line joining the 4.4.1 Thedistancemeasuringsystem,adirectreading platens are not affected and are retained at their scale isfittedto permitmeasurementofthedistance originalvalues. WI, W2 and W3 arewidthsat three 'D' between specimen platen contact points. different locationsof the actual fracture surface or Measurementsof 'D' shouldbetoanaccuracyof±2 minimumcrosssectionalarea. ThusWxDrepresents percent of D or better irrespective of the size of the minimum cross sectional area through loading specimentested. points[Fig.3(d)]. 4.5 LoadingPlatens 4.4.2 Aninstrumentsuchascalipersorasteelruleis requiredtomeasurethewidthWofspecimensforall 4.5.1 Loadingplatensshallbeconicalwith60°angle butthediametricaltest. andtheradiusofcurvatureoftheconetruncationshall be5mmasshowninFig. 1. The60°coneandthe5 4.4.3 Themeasuringsystemshouldallowacheckof mm radius spherical truncation shall meet the'zerodisplacement'valuewhenthetwoplatensare tangentially. (a) L >0·50 O·3W<0<W (c) SECTION THROUGH LOAOING POINTS WITH MINIMUM CROSS SECTIONAL AREA (d) We. ¥It... ~z+W! Alldimensionsinmillimetres, FIG.3 SPECIMENSHAPEREQUIREMENTFOR (a)THEDIAMBTRALTEST,(b)THEAXIALTEsT,(c) THE BLOCKTEsT,AND(d)THEIRREGULARLUMPTEsT 3