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है”ह”ह

IS 11105 (2004): Design and Construction of Tunnel Plugs -Code of Practice [WRD 14: Water Conductor Systems]

IS 11105:2004

Indian Standard

DESIGN AND CONSTRUCTION OF TUNNELPLUGS — CODE OF PRACTICE

(First Revision)q

ICS 93.16

G BIS 2004

BUREAU OF INDIAN STANDARDSMANAK BHAVAN, 9 BAHADUR SHAH ZAFAR MARG

NEW DELHI 110002

August 2004 Price Group 5

?!!;

Water Conductor Systems Sectional Committee, WRD 14

FOREWORD

This Indian Standard (First Revision) was adopted by the Bureau of Indian Standards, after the draft finalized bythe Water Conductor Systems Sectional Committee had been approved by the Water Resources Division Council.

Diversion tunnels are constructed to divert water of a river during construction stage of a dam. These tunnelswould need to be suitably plugged after the utilization of diversion works. The tunnel plugs resist the entireunbalanced water pressure and transfer it to the surrounding rock. The seepage/leakage is kept to a minimummanageable quantity.

To facilitate construction, adits are provided at one or more intermediate points of long tunnels. These adits haveto be suitably plugged before commissioning of the tunnels.

This standard was first published in 1984. This revision has been taken up to include construction aspects of thetunnel plugs to make this standard comprehensive.

There is no 1S0 Standard on the subject. This standard has been prepared taking into consideration the practicesprevalent in the field in India.

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

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 significant places retained in the rounded offvalue should be the same as that of the specified value in this standard.

.“

IS 11105:2004

Indian Standard

DESIGN AND CONSTRUCTION OF TUNNELPLUGS — CODE OF PRACTICE

(First Revision)

1 SCOPE

1.1 This standard covers design and constructionaspects of tunnel plugs including keys, concreting,grouting and cooling of concrete.

1.2 This standard does not cover the criteria forsuitability or otherwise of providing solid concrete plugor concrete plug with gated access for facilitatinginspection.

1.3 This standard does not cover design of adit section,structural design of gate and its recess in the body ofthe plug,

2 REFERENCES

The following standards contain provisions whichthrough reference in this text, constitute provisions ofthis standard. At the time of publication, the editionsindicated were valid. All standards are subject torevision, and parties to agreements based on thisstandard are encouraged to investigate the possibilityof applying the most recent editions of the standardsindicated below:

IS No.

456:2000

457:1957

5878:(Part 7) 1972

14591:1999

3 MATERIAL

Title

Plain and reinforced concrete —Code of practice ~ourth revision)

Code of practice for generalconstruction of plain and reinforcedconcrete for dams and other massivestructuresCode of practice for construction oftunnels conveying water: Part 7GroutingTemperature control ofmass concretefor dams — Guidelines

Plain and reinforced concrete/work shall conform toIS 456.

4 LOCATION

4.1 For permitting utilization of diversion tunnels asspillway tunnels, outlet tunnels, tail race tunnels, etc,the plugs shall be placed immediately upstream of the

intersection point of the diversion tunnel with thevertical/inclined shaft, water conductor tunnel, etc.Additional concrete may be required to be placedfor necessary hydraulic profile at the junction (seeFig. 1).

4.2 For plugging construction adits, solid concreteplugs shall be provided at their junctions with maintunnel. Gates if provided, shall be as close to the tunnelas possible to cause minimum hydraulic losses. It shallopen inside the tunnel so that water pressure shall forceclosure and sealing of gates (see Fig. 2).

5 TYPES OF PLUGS

Plugs are mainly classified as:

a) Solid concrete plug (see Fig. 1); and

b) Gated plug (concrete plug with gated opening,see Fig. 2).

6 CONSTRUCTION FEATURES OF THECONCRETE PLUG

6.1 Wedge shaped keys are generally provided forbetter plug action.

6.2 Keys shall be provided in rock/concrete interfaceand within concrete to ensure effective plug action byproviding adequate bearing of the plug concrete onthe tunnel lining or plug concrete/tunnel lining on thesurrounding rock. The keyways in the tunnel liningmay be filled up with lean concretelwood packinglmasonry to ensure smo@h flow of water duringdiversion stage and this shall be removed prior to theconcreting of the plug.

6.3 Keyways provided in the fust stage plug concreteshall be designed for anticipated horizontal thrust.Keyways thus provided shall be filled up with thematerial given in 6.2 so long as the tunnel is used forrestricted flow purposes.

6.4 The solid concrete plug may be provided instages where required from operational/functionalrequirements for diversion tunnels (see Fig. 1). Forensuring proper bonding between existing andsubsequent stages of concrete chippinglroughening of

1

IS 11105:2004

I.Ll

LEGEND:

~ INITIALLININGCONCRETE

~ SECONDSTAGECONCRETE

X-J

SECOND STAGECONCRHE

v- C.L. OF TUNNEL

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E

SECTION X=X

FIG. 1 TYPICALSECTION(SHOWINGCONCRETEPLUG IN STAGES)

2

/- C.L.OF TUNNEL

Ll-—------ -—-—o—-—- =-4

C.L

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I C.L. OF ADIT

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PLUGCONCRETE .(2ND STAGE) 7(

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FIG. 2 PLAN SHOWINGGATEDPLUG

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1S 11105:2004

existing concrete should be carried out along withprovision for suitable dowels.

6.5 The reinforcement of the tunnel lining shall be soplaced that this does not get damaged and hinder duringthe chipping of concrete keys.

6.6 The length of concrete plug in the tunnel ifprovided, without keys will depend mainly uponfrictional resistance offered by the surrounding initialconcrete or rock and bearing on the rock dependingupon shape of the plug.

6.7 Adequate provisions shall be made for dewateringduring construction.

6.8 To facilitate grouting a gallery may also be left inthe plug wherever required.

7 DESIGN OF PLUG

7.1 Design Head

7.1.1 Plugs in the tunnel are designed for the maximumreservoir level with no flow or minimum flow in thetunnel.

7.1.2 Allowance shall be made for increase in waterhead in reservoir due to any rare situations like wavebuild up, surge and water hammer effects, if applicable,in case of sudden stoppage of flow in the tunnel.

7.2 Plug Length

7.2.1 The length of the plug shall not be less than theexcavated diameter of the tunnel. The overall length ofthe plug may be increased to keep an allowance for sealsat the near ends. The plug length maybe calculated basedon any of the following formulae as applicable:

a) Length of the plug >

b) Length of the plug 2

c) Length of the plug 2

NOTES

Hydrostatic force on theplug due to water head

Permissible averageshear stress x PerimeFerof tunnel section

Hydrostatic force on theplug due to water head

Frictional resistance perumt length of the plug

Hydrostatic force on theplug due to water head

Frictional resistance ofplug and shear resistanceof anchors per unitlength of the plug

1 Value of permissible average shear stress/shear frictionbetween the plug and surrounding concrete/rock shall allowfor any imperfections in contact grouting between the phrgand the tunnel lining. Conservative values with ample safetyfactors shall be considered.

2 Values of permissible shear and frictional resistance shall bevalidated where required at site.

7.2.2 It is preferable to provide the whole length ofplug in one block without arty construction joint.

8 DEPTH OF KEYWAYS

8.1 Key in Concrete/Rock

The depth of key maybe calculated from the averagebearing stress in concrete/rock from the followingformula. The permissible stresses in concrete shall bein accordance with IS 456. In many cases the stressesin concrete will govern as rock would be generallystronger than concrete.

Hydrostatic force on the plugAverage bearing =stress Effective projected bearing

area

NOTES

1 Effective projected bearing area shall be assumed 75 percentof the total projected bearing area of the keys to allowimperfections in grouting.

2 The depth of any key where feasible shall not be less than450 mm.

9 GROUTING

9.1 General

9.1.1 Grouting is required to improve the quality ofthe rock by filling the fissures/voids of the rocksurrounding the plug. This shall also be done to ensurebetter shear friction.

9.2 Types of Grouting

9.2.1 Following are the two types of grouting:

a) Consolidation grouting, and

b) Contact grouting.

9.2.1.1 Consolidation grouting is done to improve thequality of bearing rock in the vicinity of plug and toreduce leakage at that location. In poor rocks,consolidation grouting is done to make good any fissuresin the rock which may either be existing previously orcaused during tunnel driving. Consolidation groutingalso reduces the possible leakage through the rock.Consolidation grouting of the rock surrounding theplug shall be done prior to the placement of the plug(see Fig. 3).

9.2.1.2 Contact grouting is low pressure groutingthrough shallow holes. Contact grouting shall be doneto fill any cracks developed at the interfaces on accountof shrinkage of concrete and to ensure better shearfriction and prevent excessive leakage along the contactofplug concrete and rockhunnel lining. It shall be done

.-%

.

4

PLUG CONCRETE

.●

s-

1S11105:2004

/

C.L. OF ADIT

ICONSOLIDATION

T GROUT HOLES

/ INITIAL LININGKY /i CONCRETE

I

FIG.3 TYPICALSECTION(SHOWINGCONSOLIDATIONGROUTING)

from the outer ends of the plugs by means of system 9.2.1.3 In case of gated plug, contact grouting mayof supply, return and vent headers embedded in the also be done by direct holes from the gallery.plug concrete. Contact grouting shall be done after 6 9.2.1.4 Grouting of rock surrounding the plug shallweeks of concreting the plug (see Fig. 4).

conform to IS 5878 (Part 7).

/

C.L, OF ADIT

CONTACT GROUTINGHOLEfl

INITIAL LININGCONCRETE

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FIG. 4 TYPICALSECTION(SHOWINGCONTRACTGROUTING)

5

IS 11105:2004

9.2.1.5 In case of excessive leakage grouting usingmicro cement and/or chemical grout shall be done toachieve the desired result.

10 COOLING OF CONCRETE

10.1 Plug concrete shall be placed at temperatures tobe determined based on cooling studies for concrete(see IS 14591 and other specialist literature). Inabsence of such studies plug concreting can be doneat a placement temperature of 130C. In caseprecooking of concrete is not possible, then post-cooling may be done by circulating chilled waterthrough coils of thin tubing installed on top of eachlift of concrete (see Fig. 5).

10.2 Special care shall be taken at lift joints to ensureadequate shear resistance.

10.3 In case of gatecl plugs, cooling of concrete maynot be required, if concreting is done in stages to reducethe thickness of concrete. Keys shall be provided infirst stage concrete for transferring the water headwhich is acting on the second stage of concrete .

11 ANCHORAGE OF MAIN TUNNEL LININGIN PLUG CONCRETE

11.1 In case of gated plug, full circular shape of lininggets broken by the access opening through the plug.The main tunnel lining would have to be supportedwith suitable arrangements. The lining may besupported on portal and concreting of this frame shall

PLUG

be done monolithic with the lining of main tunnel.Fig. 6 shows main tunnel lining of the plug accessportion (supported on the rectangular frame aroundthe access through plug).

11.2 In the portion, where main tunnel lining getsbroken by the access opening through the plug, thetunnel invert and overt shall be anchored to theexisting rock, as shown in Fig. 6, so that the loadsacting on the straight leg between invert and portal,and overt and portal are not transferred to the tunnellining.

12 BLOCKOUT FOR GATE

12.1 Blockouts for embedments of gate shall besuitably anchored into the plug concrete.

12.2 Double water seals shall be provided in theblockout to check leakage of water through the jointsbetween the plug concrete and blockouts.

13 CLEARANCE OF SILT IN GATE CHAMBER

13.1 In case of gated plugs with access through theplug, there are chances of silt deposits in gate chamberbehind the gate. This deposited silt needs clearance toavoid any difficulty in operation of the gate.

13.2 Suitable arrangements shall be provided toremove the anticipated silt. This may be done byinjecting air/water jet under pressure through theaccess of plug.

FC.L. OF ADIT

●...!** .

INITIAL LINING. .

\&,. ..;:

CONCRETE .: :

COOLING TUBES

LIH LINES

FIG. 5 TYPICALSECTION(SNOWINGCOOLINGARRANGEMENT)

6

IS 11105:2004

x1

I

QI&lUNNEL

SECONDCONCRE

/ \ —WI I

FIG. 6A PLAN AT JUNCTIONOF H.R.T. WITHADIT

IS 11105:2004

rANCHORS

SHEAR STRIRRUPS -

MULTILEG SHEAR STIRRUPS J ISECTION X -X

FIG. 6B ANCHORAGEOF MAIN TUNNELLINING

IS 11105:2004

ANNEX A

(Foreword)

COMMITTEE COMPOSITION

Water Conductor Systems Sectional Committee, WRD 14

Representative(s)Organization

Central Water Commission, New Delhi

Andhra Pradesh State Electricity Board, Hyderabad

SW D. K. MEHTA(Chairtnaa)

CHIEFENGINEER(CIVIL)SUPEIUNTENDINGENGINESR(Alternate)

CHIEFENGINEER(CtvrL)AoDmoNALCmEF ENGtNEER(DES) (Alternate)

Assam State Electricity Board, Guwahati

CHIEFENGINEER(BSL)DIIWCTOR(WATERI&GULATtON)(Mterrrale)

Bhakra Bess Management Board, Nangal Township,Hlmachal Pradesh

Central Mining Research Institute, Roorkee DR V. V. R. PRASADSHMANILSWARUP(Alternate)

Central Soil and Material Research Station, New Delhi DMI?CTORDEFOTYDIRECTOR(RM) (Alternate)

DR I. AZAILUAHSmuR. M. SINNARKAR(Merrraie)

Central Water & Power Research Station, Pune

‘DIRSCTOR(SSPH )DSRSCTOR(HCD) (NW&S) (Alternate)

SHRSV. K. KAPURWIG T. K. DAS(Alternate)

Central Water Commission, New Delhi

Consulting Engineering Services (India) Ltd, New Delhi

Smr G. K. KAIMHASmu D. N. BHMTACHARVYA(Alternate)

Geological Survey of India, Faridabad

Himachal Pradesh State Electricity Board, Sundernagar CHIEFENGINEER(DESIGN)SUPERUVtENDINGENGINEER(Alternate)

Cr+mFENGINEER(CANALS)sUFEMNTSNDINGENGINEER(CDG) (Alternate)

Irrigation Department, Govt of Haryana, Chandigsrh

Irrigation Department, Govt of Maharashtr4 Nashik SUPERSNTSNDINGENGINEEREXSCLMVEENGINEER(Alternate)

CrrrEFENGINEER(CIVIL)SUPERINTENDINGENGSNEER(SCC) (Alternate)

Irrigation Department, Govt of Punjab, Chrmdigarh

Irrigation Department, Govt of UP, Roorkee

Irrigation Department, Govt of Kamatak& Gulbarga Dktrict

CNJSFENGINSSR(DE.SIGN)suPmNTsNLlINGENGINEER(Alternate)

CsirEFENGINEERDEFUrYCmF ENGINEER(Afternate)

Jaiprakash Indust;es Ltd, New Delhi Smu D. G. KADKADBSmu NARENDSMStkGH(Alternate)

CmEF ENGINESR(CrvrL DESIGN)SUFESUNTENDINGENGINEER(Ahernafe)

Karnataka Power Corporation Ltd, Bangalore

DSPUTYCrirEFENGSNEER(CrvrL)Kerala State Electricity Board, Thimvanaothapuram

Nathpa Jhrrkri Power Corporation Ltd, New Delhi DIRECTOR(CtVIL)SmuR. K. SHARMA(Alternate)

Smu V. K. GUPTASmu SATYANARAYAN(Alternate)

National Hydroelectric Power Corporation Ltd, Faridabad

North Eastern Electric Power Corporation Ltd, SIrillong Srmr A. C. GoSWAMISHFOUTPALBORA(Alferrrate)

Public Works Department, Govt of Tamil Nadu, Chennai Smu M. DrrRAmAI

9

IS 11105:2004

Organization

R.J. Shah & Co Ltd, Mumbai

Rashtrya Pariyojana, Nirman Nigam Ltd, New Delhi

Tamil Nadu Electricity Board, Tamil Nadu

Tehri Hydro Development Corporation Ltd, Rlshikesh

TEXMACO Limited, Kolkata

Water & Power Consultancy Services (I) Ltd, New Delhi

Water Resources Development Centre, Roorkee

BLS Directorate General

Representative(s)

Sma S. M. SHAH

Smu S. V. PATWARDHANSHMR. C. RASTOGI(,4/fernate)

CHSEPENGINSER(JiYDROPROJECT)SUPEMNTENOtNGENGINEER(Alternate)

SHRIG. M. PRASADSrmrSHAILENDRASINGH(Alterrraie)

Smr S. R. SINHASHIUSum BANERJEE(Ahernafe)

Smu P. L. DIWANSHSUA. P. CHOWDHURY(Alternate)

DR NAYANSHARMADR B. N. ASTHANA(Alternate)

SHruS. S. Smn, Director & Head (WRD)[Representing Dkector General (Ew#icio)]

Member-SecretarySHRIMATIROSYDHAWAN

Joint Director (WRD), BIS

10

f

Bureau of Indian Standards

BIS is a statutory institution established under the Bureau of Indian Standards Act, 1986 to promoteharmonious development of the activities of standardization, marking and quality certification of goodsand 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 reviewedperiodically; a standard along with amendments is reaffirmed when such review indicates that no changes areneeded; if the review indicates that changes are needed, it is taken up for revision. Users of Indian Standardsshould ascertain that they are in possession of the latest amendments or edition by referring to the latest issue of‘BIS Catalogue’ and ‘Standards: Monthly Additions’.

This Indian Standard has been developed from Doc : No. WRD 14 (274).

Amendments Issued Since Publication

Amend No. Date of Issue Text Affected

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