is 12634 (1989): method of determination for direct shear
TRANSCRIPT
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.
इंटरनेट मानक
“!ान $ एक न' भारत का +नम-ण”Satyanarayan Gangaram Pitroda
“Invent a New India Using Knowledge”
“प0रा1 को छोड न' 5 तरफ”Jawaharlal Nehru
“Step Out From the Old to the New”
“जान1 का अ+धकार, जी1 का अ+धकार”Mazdoor Kisan Shakti Sangathan
“The Right to Information, The Right to Live”
“!ान एक ऐसा खजाना > जो कभी च0राया नहB जा सकता है”Bhartṛhari—Nītiśatakam
“Knowledge is such a treasure which cannot be stolen”
“Invent a New India Using Knowledge”
है”ह”ह
IS 12634 (1989): Method of determination for direct shearstrength of rock joints [CED 48: Rock Mechanics]
IS 12634 : 1989
Indian Standard Reaffirmed 2010
ROCK JOINTS DIRECT SHEAR STRENGTHLABORATORY METHOD OF DETERMINATION
— —-
UDC 624.121.37 : 624.131.439.5
© BIS 1989
BUREAU OF INDIAN STANDARDSMANAK BHAVAN, 9 BAHADUR SHAH ZAFAR MARG
. NEW DELHI 110002
August 1989 Price Group 2
AMENDMENT NO.1 DECEMBER 2007TO
IS 12634 : 1989 ROCK JOINTS - DIRECT SHEARSTRENGTH - LABORATORY METHOD OF
DETERMINATION
(Page 3, Fig. 3) - Substitute the following for the existing:
'SHEAR STRESS' for 'SHEAR STRENGTH' in the title ofr-axis,
'0.8 MPa' for '0.8 MPalmma" and
'2.5 MPa' for '2.5 MPalmma, .
(Page 4, clause 7.3, lines 2 and 4) - Substitute 'Normal Force (PJ' for'Total normal stress (Pn) , and 'Shear Force (P.)' for 'Total shear stress (P.)'respectively.
(Page 4, Fig. 4) - Substitute 'SHEAR STRENGTH' for 'SHEAR STRESS'.
(Page 4, clause 8.1, Note, line 2) - Substitute 'correlation' for 'corelation' .
(CED48)
Rcpropaphy Unit,BIS,New Delhi. India
It
Rock Mechanics Sectional Committee. IDe 73
FOREWORD
This Indian Standard was adopted by the Bureau of Indian Standards on 16 January 198~t after thodraft finalized by the Rock Mechanics Sectional Committee had been approved by the Civil Enlineerins Division Council.
Thr direct shear strength measured in the laboratory can be used to realistically assess the Itrenath orrock joints. This test measures the peak and residual direct shear strenJth of rock joint samples a8 afunction of stress normal to the sbearing plane. The results of this test can be used directly in thestability anal)"is only if the type and size or rou,hness irresu1arities of the tested plane are similarto those obtained in the field on a larger scale. I this is not the case. then the laboratory value ofpeak strength should be suitably modified. IS 11315 ( Part 4 ) : 1987 'Method for the quantitativedescriptions of discontinuities in rock masses : Part 4 Roughness' may be referred for non-linear shearstrenath crittria ofjoints.
For the purpose of deciding whether a particular requirement of this standard is complied withJ~theflnal value. observed or calculated, expressing the results of a test or anal)'s;s, shall be rounded off inaccordance with IS 2 : 1960 'Rules for rounding off numerical values (revised )'. The number ofsi,nificant places retained in the rounded off value should be the same as that of the specified value inthis standard.
IS 12634 : I'"
Indian Standard
ROCK JOINTS - DIRECT SHEAR STRENGTH '"LNlORATORY METHOD" OF DETERMINATION
1 SCOPE
1.1 This standard covers a laboratory method ford~termiD8tion of direct shear strength of rockjoints.
2 REPERENCES
2.1 The followinS Indian Standards are necessaryadjuncts to this standard:
., APPARATUS
4.1 Suitable materials to protect the specimenfrom mechanical damaae and to maintain thewater content both during cutting and transit tothe laboratory, such as, protective packiog andwax, or other similar water proofiD8 materials.Suitable materials are also required for holdio.the specimen together, such 8S, binding wire ormetal band.
IS 11358: t98?
3 'TERMINOLOGY
4.2 Equipment for specimen preparation shouldIS No. Title include core drills, percussive drills of suitable
diameter, rock saws, chisels and hammers forIS 1131S ( Part 4) : 1987 Method for the quan- cutting the specimen and the equipment for
titative description of measuring the dip, direction, roughness and otherdiscontinuities in rock characteristics of the test horizon.mass : Part 4 Roughness
4.3 Equipment for mounting the specimen shouldGlossary of terms and include specimen carriers forming a dismountablesymbols relating to part of the test equipment, mixing utensils alongrock mechanics with strong encapsulating material, such as,cement,
plaster or resin.
4.4 Test Eqalpaa_
3~1 For the purpose of this standard, the defini- Along with the shear box ( see Fig- 1 ), the testtions liven in IS 11358 : 1987 shall apply. system should comprise the following:
NORMAL LOAD
SHEARLOAD
~~~~~~~~~~~~~lOW FRICTfONARRANGEMENT
PIG. 1 ARRANGEMENT POI. THE LABORATORY DIRECT SHBA" TEST ON Rocu
1
IS 12634: 198'
mechaaical iDtearity of tile ~meD ahould bepreserved by bindiDI tiptly with wire or tapewhich ia to be kept in position until tho commencement of the test.
5.2 Specimens which are Dot eDC8psu!atetl immediatc:ly for testin. should be liven a waterproofcoatlna, labelled and packed to avoid pouib1edamage in transit to the laboratory. Special careshou.ld be taken while transportin, fraillespecimens.
~.3 After the specimen is taken to the laboratory.Its protective packing is removed and the blocksupported in one of the carriers so that the horizonto .be t~sted is secured in I?roper position andorlentattcn, The encapsulating material is thenpoured and allowed to set. The other half of thespecimen is also similarly encapsulated. A clearzone of about S mm on either side of the shearplane should be free from the encapsulation. Forrock joints, plaster of Paris may be used as theencapsulating material.
6 TEST PROCEDURE
6.1 COlllOlldadoD
4.4.3 Equipment for Measuring the Normal andShear Forces Independently
The accuracy shall be ±1 percent of the maximumvalues of these forces during a test. This equipment should be calibrated before the test and therelevent charts/tables should be supplied with thereport.
6.t.l Before the actural commencement of thetest, the specimen is allowed to consolidate underfull normal load for dissipation of pore waterpressure in the rock material and the filling
4.4.4 Suitable Devices for Measuring the Normal material adjacent to the shear plane.and Shear Displacements During the Test NOTB - The sample should be saturated before tOlt
for ftDdina values In saturated condition_
".4.1 Jt Suitable Hydraulic, Pneumatic Dr Mechanical System
It shall be capable of applying normal loads onthe shear plane of the specimen in such a mannerthat the load is uniformly distributed over theplane to be tested. The normal load should passthrough the centre of the shearing area. Thesystem should be capable of maintaining thenormal loads consistent to within ± 2 percent ofthe desired load.
4.4.Z A Suitable Hydraulic Jack or a MechanicalGear Drive System
This system is for applying shear loads uniformlyalondthe half-face of the specimen with the resultant acting in the plane of shearing. It sbouldhave rollers, cables or other low friction deviceto ensure that the resistance of the equipment toshear displacement is within 1 percent of themaximum shear force applied during a test.
These may include micrometer dial gauges, displacement transducers, etc. The shear displacementmeasuring system should have a travel greaterthan 10 percent of the specimen length and withan accuracy of o· t mm. The normal and lateraldisplacement measuring system should have atravel more than 20 mm and an accuracy of O·OSmm. In the case of displacement transducers,the relevant calibration data should be includedin the report.
5 SPECIMEN PREPARATION
5.1 A suitable test horizon should be selected andits relevant geological characteristics, such as, dip,dip direction, etc, are recorded. Block or corespecimens are then collected from the said testhorizon in such a manner that the specimen issubjected to least disturbances and its location
. within the test horizon should be such as to allowmounting without any further trimming in thelaboratory and with sufficient clearance foradequate encapsulation. The test plane shouldbe square as far as possible and with a minimumarea of 2 500 mm l • It should be smooth and flatin comparison with the sjze of the specimen. The
6.1.2 After mounting the specimen in the shearbox, all gauges are checked and a preliminary setof load-displacement readings are taken.
6.1.3 Normal load is then gradually increased tothe specific value. The normal displacement( consolidation) of the specimen is recorded as afunction of applied loads and time as shown inFig. 2.
6.1.4 The consolidation of the specimen is considered complete when the rate of change of normaldisplacement is Jess than O·OS mm in 10 minutes.
6.2 Sbearl..,
6.2.1 The object of sbearing is to establish thepeak and residual values of direct shear strenathof the test horison.
~.2.z The shear ror~e should be applied either inIncrements or continuously in such a way 8S tocontrol the rate of shear displacement.
6.2.3 The rate or shear displacement should beless than 0·1 mm/min in the 10 minute periodjust
2
IS 12634: 1989
e-0·2S~."' E...
"c<3-....ZLU2:w -0·50uet-A0...tn0
...<t
--0-75~ax0z
-1·000·1 10 100 1000
ELAPSED TIME) min
o,...------------~-.....---------..
FIG.2 CONSOLIDATION CUR.VES FOR DIRECT SHEAR TEST SHOWING ESTIMA.TION OF t 100prior to takina readings. This rate may be mente Approximately, 10 sets of readings shouldincreased to not more than O·S mm/min between be taken before the peak strength is reached.cODleCutive sets or readinp provided that ~be peak 6.2.4 Once the peak strength is reached, thestrength is properl)' recorded. When testing clay readinss should be taken at increments of O·S mmfilled discontinutiOl, or in a drained test, the total shear displacements as required to adequatelytime to reach the peak strensth should exceed 6 definethe force-displacement curve shown in Fig. 3.times t 100 as determined from the consolidation The rate of shear displacement should be 0-02 tocurve in Fig. 2. If required, the rate of shear can 0-2 mm/min in the 10 minute period just before abe reduced or the application of subsequent shear set of readings is taken and may be increased toforce increments delayed so as to meet tbis require- not more than I mm/min between sets of readings.
".-.------------....12
eee
3 <2..."2 :
, 2
~. 8 I 1~, C
%.. ,... I 0 ~~ 6 {PEAK I ~~ ,tI' \ STRENGTH : ., -'
=; \ 'RES'OUAL -2 ~• '-·----- ,~STRENGTH ~
~ STAGE I ..t- STAGE -3 z~ CJft •• k.f/c",2 .n -2Skgf/cm2
.(0.. MP./mm2) (2.SM.-./rnrr1°0 .10 20 30 '0 50 .0 70
SHEAR O'SPt.ACEM£NT.41.mm
FlO. 3 SHBAR STIlESS - DISPLACEMENT GRAPH
3 ·
NORMAL STR!SS,C1n
"1c
1Io--'~------------7 CALCULATIONS
6.1.7 At the end of each test, the shear planeshould be exposed and fully described in thereport. The area of the shearins surface sbould bemeasured and photographs of the same should betaken, if required. Samples of rock, the fillmaterial and the shear debris should be subjectedto index tests.
IS 12634: 1_
6.2.5 The residual shear strength value can be 7.5 From the combined results or all tatestablished when the sample is sheared at a con- specimens, staph. of peak and residual shearstant normal stress and a sufficient number of sets strenath VI normal stress are plotted to obtala theof readinp show Jess than S percent variation in strenath parameters, ~, 4-6, ~" c and c' as Ih-lWDshear stress over a shear displacement of 10 mm. in Fi,. 4.
6.2.6 After establishing one value of the residualshear strength, the normal stress may be variedsuitably and the specimen reconsolidated undereach new normal stress and the shearin. continuedas in earlier clauses to get additional values ofresidual shear strength.
7.1 A consolidation curve as shown in Fig. 2should be plotted for the consolidation stale ofthe test. The time t 100 required for completeprimary consolidation is determined by constructing tangents to the curve. The time required toreach the peak strength value should be ,reaterthan 6 times t 100 to allow complete dissipationof pore pressure.
7.2 The displacement readings are averaged toobtain mean values of norma) and shear displacements. Lateral displacements are recorded only toobserve the specimen behaviour during the test. Ifthese are appreciable, they should be used incalculating the correct contact area.
7.3 The normal and shear stresses are calculated as
Normal stress an = Total ~ormal stress ( Po ).Shearing Area ( A )
Shear Stress t - Total shear stress ( p. )- Shearing Area ( A )
NOTES
I The effect of primary wakeness or joint surface inrock mass should be accounted for [Ie~ IS : J13J5( Part 4 ) : 1987 ].
2 Eft'ective stress should be used If the jOiDt lurfacei. in water.
. 7.4 For each test, grapbs of shear stress andnorma) displacements vs shear displacement areplotted as shown in Fig- 3. The Iraphs areannotated to indicate the nominal normal stressand any chan,es in normal stress during sheariog.The values 0 peak and residual shear strength,the normal stresses, and shear and normaJ displacements can beabstracted from these araphs.
FIG. 4 SHEAR STIlESS - NORMAL STRBSSRELA.TIONS
8 REPORTING OF RESULTS
8.1 The report of tests should include a schematicdis8ram and description of the test equipment;description of the methods used for taking,packing, transporting, storing and mouDtina of thespecimen; and the method of testing.
NOTE - The Don-linear peak atreqth curve ma,be reported by co-relation [ ••• IS 11315 ( Part 4) :J987 ].
8.1 Full geological description of the intact rockmass, sheared surfaces, fil1ins material and thedebris should be given along with index tests dataproviding information about the roughness profillerwater content, grain size distribution and Atterberglimits of the fill material.8.2.1 Diagrams or preferably photographs shoWin,the sample location, dip and dip direction of thetest horizon and any other features of importance.
8.2..2 For each test conducted. a set of data tables,consolidation, curve, Iraphs of shear stress andnormal displacement va shear displacement (asshown in Fi,. 2 and 3 ) should be Biven.
8.2.3 Abstracted values of peale and residual shearstrength should be tabulated with correspondinavalues of normal stress. shear and normal displacement.8.2.4 For shear strength determination as a whole.graphs of peak and residual shear strenlth .,.normal stress toaether with the derived vafues ofshear strength parameten (aee FiB. 4) shouldalso be liveD.
4
StaDdani Man
The use or the Standard Mark is lovemed by the provisions or the .,." of I....St.da"d, Act, 1986 and the Rules and Re,ulations made thereunder. lbe Standard Mark onproductscovered by an Indian Standard conveys tbe aauranee that they have been producedto comply with the requirements of that standard under a well defined Iystem of inspection.testina and quality control which is devised and supervised by DIS and operated by theproducer. Standard marked products are also continuously checked by DIS for conformityto that standard as a further safeauard. Details of conditions under which a licence for theOle of tho Standard Mark may be lranted to manuraeturen or producen may be obtainedrrolD the Bureau or Indian Standards. .
a.eau 01ladl. Staclanl.
· DIS is a Itatutory institution established u:ader the Bu'«IU o/I"dlrm Standara .4et. 1'8' to promoteharmonious development of the activities of standardization, markin. and quality certifiCation of loodIand attendinl to connected matters in the country.
Copyr'."t
BIS has the copyright of all its publications. No part of these publications may be reproduced inany form without the prior permission in writios of DIS. This does not preclude the free use, in thecourse of implementing the standard, of necessary details, such as symbols and sizes. type or Ifadedesignations. Enquiries relating to copyright be addressed to the Director ( Publications ). BIS.
Reyl.'OD of Indian Stud.rd.
Indian Standards are reviewed periodically and revised, when necessary and amendments, if any, areissued from time to time. Users of Indian Standards should ascertain that they are in possession ofthe latest amendments or edition. Comments on this Indian Standard may be sent to DIS livin. thefollowing reference:
Doc: No. DOC 73 (4387)
Amendments ISltted Since Pabllcatloa
Amend No. Date of Issue Text Affected
--------------------------------------
BUREAU OF INDIAN STANDARDS
Headquarters :
Manak Bhavan, 9 Bahadur Shah Zafar Mar•• New Delhi 110002Telephones: 331 01 31, 331 13 75
Regional Offices :
Central: Manak Bhavan, 9 Bahadur Shah Zafar MaraNEW DELHi 110002
Telegrams : Manaksanstha( Common to all Offices )
Telephone
{331 01 31331 13 75
Bastern : 1/14 C. I. T. Scheme VII M, V. I. P. Road, ManiktoJaCALCUTTA 700054
Northern: SCQ 445-446, Sector 3S-C, CHANDIGARH 160036
Southern: c i, T. Campus, IV Cross Road, MADRAS 600113
Western: ManakaJaya, E9 MIDC, Marol, Andheri ( East )BOMBAY 400093
Branches: AHMADABAD. BANGALORE. BHOPAL. BHUBANESHWAR.GUWAHATI. HYDERABAD. JAJPUR. KANPUR. PATNA.TRiVANDRUM.
3624 99
{2 J8 433 1641
{
41 244241 25 1941 29 16
'329295
Prioted at Printwell Printers, Delbi, India