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IS 13946-4 (1994): Determination of rock stress-Code ofpractice, Part 4: Using flat jack technique [CED 48: RockMechanics]

. .

IS 13946 ( Part 4 ) : 1994

Indian Standard

DETERMINATIONOFROCKSTRBSS- CODEOFPRACTICE

PART 4 USING FLAT JACK TECHNIQUE

UDC 624-121.4

o BIS 1994

BUREAU OF INDIAN STANDARDS MANAK BHAVAN, 9 BAHADUR SHAH ZAFAR MARG

NEW DELHI 110002

March 1994 Price Group 5

l

Rock Mechanics Sectional Committee, CED 48

FOREWORD

This Indian Standard ( Part 4 ) was adopted by the Bureau of Indian Standards, after the draft finalized by the Rock Mechanics Sectional Committee had been approved by the Civil Engineering Division

Council.

Vertical stress on a rock mass varies in a more predictable fashion than horizontal stress because the former is primarily affected by the weight of overburden.

When an opening is introduced in the rockmass, the natural state of stress is disturbed locally as the rock mass attains a new state of equilibrium. The stress around an opening resulting from various man-made activities is termed ‘induced stress’ as opposed to virgin stress or absolute stress which describes the original, undisturbed state of stress. The natural state of stress is often termed as in situ stress.

Underground in situ stress is sometimes sufficiently high ( relative to the rock mass strength ) to cause rock bursting spalling, buckling, heaving, or other ground control problems. In such cases, knowledge of the state of in situ stress is of critical importance to the design and construction of engineering structures in a rock mass. Even in cases where the effects of stress are less dramatic, the optimum shape, orientation and layout of under-ground structures, as well as the effectiveness and ultimate cost of rock support systems, can be significantly influenced by the in situ stress.

Factors affecting the magnitudes and orientation of in situ stress include the weight of overlying and materials, geologic structures ( on local and regional scales ), tectonic forces within the earth’s crust, residual stress and the thermal stress. The complexity of the relations between theses factors and the in situ stress usually prohibits reliable estimation of rock stress. In addition, stress cannot be measured directly, and therefore, rock stress determination techniques rely on the measurement of some response ( fcr example displacement, strain, deformation ) that is induced by a disturbance of the rock mass. This measured response of rock in a stress-disturbed zone ( for example, the wall of a tunnel ) is extrapolated, from the opening outwards, through a numerical model or analytical techniqu- es or measurements must be made via a drillhole that extends into an undistrurbed region of the rock mass.

Several methods have been tried to arrive at a reliable means of measuring in situ stress. Each offers different advantage and disadvantages with respect to a particulur applicable.

Different methods for measurement of rock stress have been covered in following four parts which have got wide acceptance :

Part 1 Using the hydraulic fracturing technique

Part 2 Using a USBM type drillhole deformation gauge

Part 3 Using a CSIR or CSIRO type cell with 9 or 12 strain gauges

Part 4 Using flat jack technique

For field use, the technique for measuring stress in rock should be simple and enable a number of measurements to be made easily. The flat jack method is one such technique. The method consists of cutting a thin slot into the rock surface by drilling a series of overlapping holes. This process relieves the rock surface of the stress which originally existed across it. Because of the stress relief, the sides of the plot converge. This is measured between two points across the slot fixed in the rock prior to cutting the slot. The convergence occurring is then neutralized by inflating a flat jack fixed in the slot and the cancellation pressure is noted, Assuming that the rock mass is elastic within range of working stress, this canceIlation pressure is taken as very nearly equal to the pressure that existed in the rock normal to the plane of slot before the slot was cut.

The main limitations of the test are : the size of the flat jack in relation to the size of the rock mass, assumption of elastic recovery, errors due to stress concentration due to driving of tunnels, etc. This test cannot be carried out at any appreciable depth from the rock surface.

In this part method covered in IS 7292 : 1974 has been elaborated further to include calibration aspect and reporting of results besides using SI units. After publication of this part IS 7292 : 1974 shall be withdrawn.

The committee responsible for the formulation of this standard is given at Annex A.

( Continued on third cover )

IS 13946 ( Part 4 ) : 1994

Indian Standard

DETERMINATIONOFROCKSTRBSS- CODEOFPRACTICE

PART 4 USING FLAT JACK TECHNIQUE

1 SCOPE

1.1 This code deals with determination of magnitude of stress in rock mass by using flat jack technique.

2 TERMINOLOGY

2.0 For the purpose of this standard, the follow- ing definitions shall apply.

2.1 Gauge Points

These are arbitrary marked points on both sides of the slots and are used as observation points for deformeters ( see Fig. 1 ).

2.2 Flat Sack

An equipment used for applying cancellation hydraulic pressure.

2.3 Gauge Length

Gauge length is the distance between two gauge points, taken on either side of the slot in the plane normal to it ( see Fig. 1 ).

2.4 Deformeter

A high precision equipment used for measure- ment of change in distance between two gauge points.

2.5 Cancellation Pressure

This is the hydraulic pressure in the flat jack at which the displcements created by cutting the slot are cancelled.

2.6 Slot Axis

This is the axis passing through the centre of the slot section and parallel to the plane of slot width and the plane of exposed rock face ( see Fig. 2 ).

3 SYMBOLS

3.1 For the purpose of this code, unless other- wise defined in the text, the following symbols shall apply ( see Fig. 2 ) :

c = half length of the slot;

co = half length of the flat jack;

j / ii I

SECTIONAL VIEW OF ROCK FACE ROCK FACE

A-D and E-H, 500 mm pair gauge point B-C and F-G, 250 mm pair gauge point

i, k 250 mm gauge length j, I500 mm gauge length

All dimensions in millimetres.

FIG. 1 DBTAILS OF SLOT AND GAUGE POINT

1

IS 13946

E =

P =

s =

Q =

w=

wo =

WI =

wp =

Wj E

( Part 4 ) : 1994

deformation modulus ( in situ );

cancellation pressure in the flat jack;

rock stress normal to the plane of the slot;

rock stress parallel to the plane of the slot;

observed displacement of the rock along the axis normal to slot at the gauge point as a distance from the slot axis;

the displacement of the rock along the axis normal to slot at the gauge point at a distance from the slot axis due to stress on an infinitely thin slot;

a correction term, for the slot of finite width 2 Y, regarded as an elongated ellipse, shall be added to W,;

displacement of the rock at the gauge point at a distance y from the slot axis due to stress Q, in the direction of w,;

displacement of the rock at the gauge point at a distance from the slot axis caused by flat jack when raised to pressure P, in direction opposite to W,

Y = distance of the gauge from the slot axis and normal to it;

y. = finite half \+idth of the slot; and

IJ = Poisson’s ratio.

4 GENERAL

4.1 The determination of rock properties by flat jack method consists in measuring the displace- ment in the rock due to cutting a slot in it. A flat jack is then cemented into the slot and pressure applied to it until the displacement created due to cutting the slot is cancelled. This cancellation pressure is then used to compute the rock properties by means of equations given in 4.3.

4.2 The method involves the following assump- tions and considerations :

a) The cutting of the slot causes a change in stress distribution in the rock which in turn produces a corresponding strain or displacement at the gauge points.

b) The strain or displacement produced by pressure in the flat jack at cancellation pressure is equal and opposite to that developed as a result of cutting of slot.

c) The application of cancellation pressure by flat jack restores the initial stress field in the rock around the slot and the can- cellation pressure is therefore eqnal to the initial stress existing within the rock ( be- fore the slot was cut ).

Value of deformation modulus E and Poisson’s ratio ( p ) has been assumed to be the same in all directions.

e) Errors due to stress concentrations due to driving of tunnels are negligible.

4.3 Theory

Since the stress system S and Q existing within the rock prior to slot cutting is compressive, the total displacement after cutting the slot is given by the following equations:

w = w,+w,+w, . . . . . (1)

W, __%I (1 --p) (a _ $)+W 1

. . . ...(2)

w =syo- 2 1 E i ( /z a - _v_ + .!rw

c > a I . . . . . (3)

WI = -w;$ . . . ...(4)

where

a= J

1+ $-

S

SLOT AXIS FLAT JACK

All dimensions in millimetres.

FIG. 2 STRESS FIELD AROUND THE SLOT

2

1s 13946 ( Part 4 ) : 1394

After the flat jack is grouted in the slot and and, when the slot was cut in vertical plane, raised to hydraulic pressure the displacement is using equation (10) of 4.3. given by: Q = 0.815 x 16.87 + 0.064 x S . . . . ..(12)

where

. . . ...(5)

a, = J

14; 0

If the pressure in the flat jack is cancellation pressure, then,

w = wj . . . ...(6)

or

Wj = W0 + WI + wZ . . . - (7)

Substituting the values of WO, WI, Ws and WI from equations 2, 3, 4 and 5 in equation 7.

s - FI P + Fz Q . . . . . (8)

where, F1 and Fz are constants and their values can be taken as 0.815 and 0.064 respectively, for a slot length ( 2c ) = 33 cm, flat jack length ( 2 c, ) = 30 cm, slot width ( 2 y0 ) = 4.0 cm, gauge length ( 2 y ) = 25 cm and Poisson’s ratio ( p ) ranging from 0 15 to 0.25. The equation (8) involves two unknowns, namely, S and Q and as such the flat jack tests are carried out in two directions, normal to each other so as to formu- late a set of two equations. These equations shall then be solved for the values of S and Q.

Thus Ph and Pv are the cancellation pressures in horizontal and vertical slot directions respec- tively, then

S = FI Ph + Fz Q a.. -. (9) Q -1. F, P, + F, S . . . . ..(lO)

NOTE - To make the equations clearer, an example is shown below:

Example: a) Length of slot 2c = 33 cm b) Length of flat jack 2c0 = 30 cm

c) Width of slot 2 yo = 40 cm

d) Gauge length 2 y = 25 cm

e) Poisson’s ratio (a typi- cal value for the rock ) EL = 0’167

f) Cancellation pressure when slot is horizontal Ph = 21’10 kg/cm’

g) Cancellation pressure when slot is vertical PV = 16’87 kg/cm’

Using the equations given in 4.3, the values of constants Fl and Fz are computed as 0.815 and O-064, respectively.

Thus when the slot was cut in horizontal plane, using equation (9) of 4.3.

S = 0.815 x 21.10 + 0.064 x Q . . . ...(n)

Q = 14.90 kg/cm2

4.4 In order to determine the principal stresses at least three tests shall be carried out at one site in three orthogonal planes. The test shall be carried out at the same site but in the zone not influenced by any previous test. For this, tests should be carried out at a distance of more than 3 times the length of the slot from the centre of the slot along its length.

4.5 Site Selection

The test site shall be as flat as possible and not adjacent to any pronounced irregularities. The test site selected should be in sound rock. The soundness shall be tested by striking the rock by a 35 mm diameter and 1 to I.5 m long steel rod. Ligther bars may not give the difference in sound. If there is any drumminess at the site, it shall be rejected. Sites where the rock is damaged as a result of weathering and stress re- laxation, shall be avoided. Sites too near a large excavated opening having loosened rocks due to blasting or points of stress concentration, such as corners shall be voided. If required, test drifts may be excavated inside the tunnel.

5 TEST EQUIPMENT

5.1 Hydraulic Pump

Capable of giving pressures up to 20 MPa. The pump shall be capable of holding a given press- ure for a period of 24 h with a maximum drop in pressure of 2 percent.

5.2 Deformeter

The deformeter consists of two arms with coni- cal legs 25 or 50 cm apart ( for 25 or 50 cm gauge lengths respectively ) centre-to-centre at their outer ends, The deformeter is provided with a precision dial gauge which records the movement of the legs. The deformeter should be sensitive to measure change in lengths up to 0.002 mm. In case such deformeters are not available damec type mechanical strain gauges of similar sensitivity may be used.

5.3 Invar Test Length

This consists of a 28 cm or 53 cm long invar bar having two small holes 25 cm apart centre- to-centre in the 53 cm bar to check the distance between the legs of the deformeter.

5.4 Flat Jack

It is a hollow square shaped hydraulic pressure cell made of 2 mm mild steel plates welded on

IS 13946 ( Part 4 ) : 1994

the four sides. A nozzle is provided for connect- ing rt with the pump as shown in Fig. 3. Oil is pumped into the cell to apply the pressure by the flat jack. It would be desirable to provide for an air exit valve in the flat jack for releasing all the air from the jack. Flat jacks of 30 cm x 30 cm, 45 cm x 45 cm or 60 cm x 60 cm may be used depending on its availability. Larger size flat jack should be preferred, particulary in jointed rock, as it gives more representative results due to stressing of larger zone of rock mass.

5.5 Gauge Pin

These are 12 mm square cross-section mild steel or brass bar 10 cm long and are wedge shaped. These are embedded in the rock face at the gauge points. The outer end of these bars are machined to have a spherical or conical seat depending upon the deformeter points. The angle of cone is exactly the same as that of the de- formeter leg. The inverted cone shall serve as gauge point and shall provide seat for the de- formeter leg. Details are shown in Fig. 4. The outer face of this end is threaded so as to cap the conical seat while gauge readings are dis- continued. This thread end shall be screwed to the holes of the spacer bar while mortaring the socket.

5.6 Jig

It isa frame made of mild steel and has location for the flat jack slot and gauge points. This ensures accuracy for the positionings and align- ment of the holes to be drilled in the rock face both for slot and gauge points ( see Fig. 5 ).

5.7 Rock Drill

Electrically operated drilling machine ( if power supply is available ) or pneumatic rock drill machine with accessories, the former being pre- ferred.

5.8 Spacer Bars

A set of 25 mm x 12 mm cross-section mild steel bars 300 mm ( or 550 mm ) long with two 10.5 mm diameter holes drilled 250 mm &- O*OOl mm ( or 500 mm f 0.001 mm ) centre-to- centre. The bar shown in Fig. 4 has a screw joint at its middle length and can be easily detached in order to unscrew the gauge pin after setting. This shall be used to position the pins accurately during their mortaring and shall ensure the gauge lengths to be within the range of the deformeter.

6 PROCEDURE

6.1 Each test location should be a firm, flat or slightly concern rock surface. The test site selected should be in sound rock. The roundness shall be tested by striking the rock by a 35 mm diameter and 1 to l-5 m long steel rod. Lighter bars may not give the difference in sound. If there is any drummines; dimensions at the site, it shall be rejected. Sites where the rock is damaged as a result of weathering and stress relaxation shall be avoided. If no suitable location is immediately available, hand or pne- umatic tool excavation should be used to pre- pare the test surface.

The distance between the test location and any significant geological drscontinuities or irregul- arities on the rock surface should be at least three times the length of the flat jack slot.

6.2 Calibration

Fiat jack suppliers should measure this difference using suitable laboratory procedures and should supply an appropriate calibration factors with each flat jack. Edge effect caused by welding, particularly for small-sized flat jacks, lead to hydraulic pressure within the jack being higher than the pressure exerted by it on the walls of the slot.

1, 25 A

i

(

300 SQ

1 +-

AXIS WELD

A

lmm APPROX

2 mm MS PLATE

ENLARGED DETAIL AT A

/NOZZLE WITH

3 ID AND 10 00

All dimensions in millimetres.

FIG. 3 DETAILS OPFLATJACK

4

IS 13946 ( Part 4 ) : 1994

I

ll$ THREADED HOLE SCREW

t--506+----- 125----+

SPACER BAR

--

DEFORMETER

GAUGE PIN

All dimensions in millimetres.

FIG. 4 DETAILS OF SPACER BAR 300 mm LONG AND GAUGB PIN

All pressure and displacement measuring devices shall be calibrated prior to its use in each test series. Calibration should be done by an inde- pendent testing laboratory.

6.3 Installation and Testing

6.3.1 Fixing the Jig

After preparing the test site, the jig shall be fixed in the desired plane, that is, the slot posi- tion shall be parallel to the plane in which the test is to be carried out. Eight holes shall be drilled for gauge points with a 20 mm drill to a depth of 10 cm from the face. The jig shall be removed after drilling the holes. The holes shall be filled with 1 : 3 cement sand mix with water/ cement ratio between 0.4 and 0.5. The gauge pins shall then be inserted ( Fig. 1 ) and held in correct positions with the help of spacer bars.

6.3.2 After the mortar has set and hardened, readings shall be taken with the help of defor- meters as specified in 6.5. These readings shall be repeated three times so as to avoid any error of measurement. These are the initial

gauge readings. The gauge pins shall remain capped unless the observations are taken.

6.3.3 The jig shall be refixed and the slot cut by 40 mm overlapping holes. The depth of holes shall be 35 to 65 cm and slot length 33 to 63 cm depending on the size of the flat jack used for the test. Gauge reading shall be observed during slot cutting also in the same order as the initial reading to observe the behaviour of the rock mass. If these readings indicate any expansion or no change over the initial gauge readings the test shall be discontinued as the rock shows some abnormal conditions at the site.

6.4 Fixing the Flat Jack

6.4.1 When the gauge readings indicate normal rock behaviour, the flat jack shall be embedded with its axis coinciding with that of the slot. Before holding the flat jack in its position, the slot shall be filled with 1 : 3 cement sand mortar at water/cement ratio between 0.4 and 0.5 and grouted under pressure or using temping rods to ensure that no air gap remains in any corner of

5

IS 13946 ( Part 4 ) : 1994

/ I 600 -

L25 @ HOLE FOR FIXING FRAME IN POSITION

All dimensions in millimetres.

FIG. 5 A TYPSCAL JIG FOR FLAT JACK OF 30 cm x 30 cm SIZE

the slot. Flat jack shall be placed in desired position and left till the mortar gains compres- sive strength of 10 MPa at ‘least. For this normally 3 to 5 days are required.

6.4.2 When the mortar in the slot has set and hardened, pressure shall be applied in the flat jack through a pump at slow but steady rate. Instantaneous raising of pressure shall be avoid- ed. The raising of the pressure in the jack to cancellation pressure shall be done in steps of 0.5 MPa for stronger rocks or less for weaker rocks depending on the condition of rock at site. These steps may be modified in the light of ex- perience at site. A minimum of 10 readings for the expected maximnm pressure range shall be taken. At every step the pressure shall be maintained for a period of 30 min after the change in gauge reading is 0.007 mm or less. All the air in the flat jack shall be bled out before raising pressure in it. The simple way of bleeding out the air is to raise the pressure in the flat jack to 0.3 MPa and slacken the pressure pipe connection and retighten. Gauge reading shall be taken before and after increasing the pressure in the flat jack. When the deformation is nearly recovered the pressure shall be retained for 24 h. The cancellation pressure for 100 percent re- covery of the total deformation shall be adjus- ed.

6.5 Observations

Gauge reading of all pair gauge points as speci- fied ( Fig. 1 ) shall be taken continuously. The readings shall consist of i,j, k and I and shall be recorded as in Tables 1 and 2. The gauge readings shall be taken right from fixing the gauge pins and shall be continued during the drilling of the slot and fixing the flat jack, and shall be plotted against time. Similarly the dis- placement recoveries shall be observed and plotted against pressure in the flat jack to record the cancellation pressure ( see Fig. 6 ). The cancellation pressure thus recorded shall be used for computing the rock properties as given in 4.3. If the deformation at all the gauge points does not recover simultaneously, an average cancellation pressure shall be taken.

6.6 Reporting of Results

6.6.1 The report shall include the following general informat ion :

a) A description of the test site location.

b) Details of the test location within the test site.

c) Rock type and local geological structures.

d) Flat jack specification and calibration.

6

e) The type, manufacturer and calibration information of the displacement gauge used.

b)

6.62 The report shall include the following detailed information for each flat jack test.

a) Initial pin displacement prior to slot ex- cavation.

c)

d)

IS 13946 ( Part 4 ) : 1994

Pin displacement following slot excava- tion.

A tabulation and graphic history of pin displacement versus flat jack pressure.

Interpretation of test results.

EXCAVATION TIME FLAT JA=ESSLJRE

FIG. 6 PIN SEPARATION VERSUS EXCAVATION TIME AND FLAT JACK PRESSURE ( NOTICE

IDENTIFICATION OE CANCELLATION PRESSURE PC )

IS 13946 ( Part 4 ) : 1994

ANNEX A

( Foreword )

COMMITTEE COMPOSITION

Rock Mechanics Sectional Committee, CED 48

Chairnron Representin.:

DR RHAWAt.3 srh_Q~ University of Roorkee, Roorkee

Members

SHKI P. K. JOIN ( dhrrrate tti Dr Bhawani Singh )

ASSISTANT RESEARCH OBFICEI~ Irrigation Department, Governn ent of Uttar Pradesh Dn R. L. CHAURAN Himachal Pradesh State Electricity Board, Shimla CHIEF EN~INEEI~ ( R & D ) Irrigation Department, Haryana

DIRECTOR ( ENQ~ ) ( Alternate ) SURI DA~ES~WAH. GANQADHAR DHAYAQUDZ Asia Foundations & Constructions Ltd, Bomba)

SHHI PRAEAS~ MADH~KAR Jostrr ( Alternate1 DR A. K. DUBE

SHR~ A. K. SONI ( Alternate) SHRI A. GEOSH

Dtz G. S. Merrnoer~a ( Alternate ) DR S. GARQOPADRYAY

SHRI S. K. MUKHERJEE ( Alternate ) DR M. R. GOYAL

Sa~r KARMVIR ( Alternate ) SIIRI B. M. RAXA GOWDA

DIRIXTOR ( Alternate ) Dn UDAY V. KULPAHNI DR R. P. K~L~ARNI MEMB~~L SECRETARY

D,IRECTOR (CJ ( Alternate ) Dr M. V. NAGENUI~A

Sartr D. N. NA~ES~ ( Alternate ) SHRI M. D. NAIR

PROF T. S. NactaRAJ ( Alternate ) SHRI D. M. PANCZIOLI

Drt U. D. DATIR ( Alternate) DR Y. V. RAX~NA PR~F T. RAYAMUI~THY

DR G. V. Rao ( Alternate ) SHRI C. B. LAKSHMANA RAO

SHRI A. K. RAMAKRIYHNA ( Alternate ) DR V. hf. SBARXA

S&RI A. K. DHAWAN ( Alternate ) MAJ S. K. SHARMA

CAPT S. P. S. KOHLI ( Alternate ) SHIII D. S. TOLIA

SHRI P. J. RAO ( Alternate ) SHRI J. VENKATRAMAN,

Director ( Civ Engg )

Central Mining Research Station ( CSIR ), Roorkee

Central Building Research Institute ( CSIR ), Roorkee

Geological Survey of India

Irrigation & Power Department, Chandigarh

Central Water & Power Research Station, Pune

Hindustan Construction Co Ltd, Bombay Irrigation Department, Maharashtra Central Board of Irrigation & Power, New Delhi

National Thermal Power Corporation Ltd, New Delhi

Associated Instrument Mfrs (1) Pvt Ltd, New Delhi

Irrigation Department, Government of Gujarat

National Geophysical Research Institute, Hyderabad Indain Institute of Technology, New Delhi

Karnataka Engineering Research Station, Karoataka

Central Soil & Materials Research Station, New Delhi

Engineer-in-Chief’s Branch, New Delhi

Central Road Research Institute, New Delhi

Director General, BIS ( Ex-o&cio Member )

Secretaries

SHRI J. K. PJ~ASAU

Joint Director ( Civ Engg ), BlS

SMT NBETA SHARMA

Deputy Director ( Civ Engg ), BIS

( Continued on page 9 )

8

1s 13946 ( Part 4 ) : 1994

( Continued from page 8 )

Field Testing of Rock Mass and Rock Mass Classification Subcommittee, CED 48 : 1

Convener

SHRI U. S. RAJVANSHI

Members

PROF K. B. AQARWAL CHIEF ENCXNEER/R-CUM DIXECTOR

RESEARCH OFFICER ( Alternate ) Ds A. K. DUBE PROB A. K. GEOSE

PROF V. D. CHOUBEY ( Alternate ) SEIRI B. M. RANE GOWDE SHRI V. K. MEHROTRA SHRI G. S. MEHROTRA

SHRI U. N. SINHA ( Alternate ) SHRI D. M. PANCHOLI

SHRI U. D. DATIR ( Alternate ) DR G. V. RAO

DR K. K. GUPTA (Alternate ) RESEAECH OFFICER ( SR & P DIVISION ) SHRI B. K. SHACMA DR V. M. SHAR~V~A

DR R. B. SIN~H ( Alternale ) SHRI VITTAL RAM

Representing

U. P. Irrigation Research Institute, Roorkee

University of Roorkee, Roorkee Department of Irrigation and Power, Government of Punjab

Central Mining Research Station ( CSIR ), Dhanbad Indian School of Mines, Dhanbad

Central Water and Power Research Station, Pune U. P, Irrigation Research Institute, Roorkee Central Building Research Institute ( CSIR ), Roorkee

Irrigation Department, Central Designs Organization, Gandhinagar

Indian Institute of Technology

Maharashtra Engineering Research Institute, Nasik National Hydroelectric Power Corporation Ltd, New Delhi Central Soil and Materials Research Station, New Delhi

Department of Irrigation, Government of Haryana

9

( Continuedfrom second cover )

In the formulation of this standard due weightage have been given to international co-ordination among the standards and practices prevailing in different countries in addition to relating it to the practices in the field in this country.

For the purpose of deciding whether a particular requirement of this standard is complied with, the final value, observed or calculated, expressing the result of a test or analysis, shall be rounded off in accordance with IS 2 : 1960 ‘Rules for rounding off numerical values ( revised )‘. The number of signi- ficant places retained in the rounded off values should be the same as that of the specified values.

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BIS is a statutory institution established under the Bureau of Zndian Standards Act, I986 to promote harmonious development of the activities of standardization, marking and quality certification of goods and attending to connected matters in the country.

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Review of Indian Standards

Amendments are issued to standards as the need arises on the basis of comments. Standards are also reviewed periodically; a standard along with amendments is reaffirmed when such review indicates that no changes are needed; if the review indicates that changes are needed, it is taken up for revision. Users of Indian Standards should ascertain that they are in possession of the latest amendments or edition.

This Indian Standard has been developed from Dot : No. CED 48 ( 5130 ).

Amendments Issued Since Publication

Amend No. Date of Issue Text Affected

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