History of Tunnels.pdf

1HISTORY OF TUNNELS IN INDIA

History of Tunnelsin India

Editors

V.K. KanjliaP.P. Wahi

A.C. Gupta

Publication No. 307

Central Board of Irrigation & Power

Tunnelling Associationof India


2008

ISBN 81-7336-314-5

_________________________________"Reproduction of any part of this publication in any form is permissible subject to proper acknowledgement andintimation to the publisher. The publisher / author / editors have taken utmost care to avoid errors in the publication.However, the publisher / author / editors are in no way responsible for the authenticity of data or information given inthe book."

Central Board of Irrigation & PowerMalcha Marg, Chanakyapuri, New Delhi 110 021Phone : 011-2687 5017 / 2687 6567 Fax : 011-2611 6347E-mail : [email protected]/[email protected] Web : www.cbip.org


Mr. Vinod KumarKonkan Railway Corporation Ltd.

Mr. P.N. VenkateshKarnataka Power Corpn. Ltd.

Mr. G.M. PrasadTehri Hydro Development Corpn. Ltd.

Mr. R.L. GuptaJaypee Ventures Pvt. Ltd.

Mr. A.K. BajajNational Highways Authority of India

Mr. B.P. AwasthiNorthern Railways

Mr. S.K. DesaiPatel Engineering Company

Mr. K.K. GuptaLarsen & Toubro Limited

Mr. S.D. JeurHindustan Construction Co. Ltd.

Mr. J. Chandrasekhar IyerCentral Water Commission

Mr. Alok GargRITES Ltd.

Dr. R.K. GoelCentral Institute of Mining and Fuel Research

Mr. Nripendra KumarCentral Soil & Materials Res. Station

Mr. P.A. KapurContinental Construction Company

Dr. Kishor KumarCentral Road Research Institute

Mr. R.S. ChauhanSatluj Jal Vidyut Nigam Ltd.

Mr. M.S. RanaKonkan Railway Corpn. Ltd.

Dr. Y. DevaGeological Survey of India

Mr. M.M. MadanNHPC Ltd.

Dr. Gopal DhawanNHPC Ltd.

Mr. M.S. BisariaGammon India Ltd.

Mr. D.P. LalIRCON International Ltd.

Dr. V.K. YadavDirectorate General Border Roads

Mr. Veer SenCentral Public Works Department

Mr. H.S. AhluwaliaMinistry of Shipping, Road Transport & Highways

Mr. P.K. GargDelhi Metro Rail Corpn. Ltd.

Prof. K.G. SharmaPresident, ISRM (India), Indian Institute of Technology Delhi

Dr. D.G. KadkadePresident, ISEG, Jaiprakash Associates Ltd.

Mr. S.M. SabnisMaharashtra State Road Development Corpn. Ltd.

Mr. Y.N. ApparaoTeesta Urja Ltd.

Mr. Manohar KhuslaniCentral Board of Irrigation & Power

TECHNICAL COMMITTEECHAIRMAN CONVENER

Prof. T. Ramamurthy Mr. V.K. Kanjlia, Secretary GeneralNew Delhi Tunnelling Association of India

MEMBERS


Tunnelling Association of India and Central Board of Irrigation & Power acknowledge the contributionsof the following organizations in compilation of the publication on History of Tunnels in India:

1. Andhra Pradesh Power Generation Corporation Ltd.

2. Bhakra Beas Management Board

3. Border Roads Organisation

4. Brihan Mumbai Municipal Corporation

5. Delhi Metro Rail Corporation Ltd.

6. Jaiprakash Associates Limited

7. Konkan Railway Corporation Ltd.

8. Maharashtra Jeevan Pradhikaran

9. Metro Railway Kolkata

10. Narmada Valley Development Authority

11. National Highway Authority of India

12. NHPC Ltd.

13. North Eastern Electric Power Corporation Ltd.

14. Northern Railway

15. NTPC Ltd.

16. Sardar Sarovar Narmada Nigam Ltd.

17. Satluj Jal Vidyut Nigam Ltd.

18. Tehri Hydro Development Corporation Ltd.

19. Water Resources Department, Govt. of Maharashtra


CONTENTS

FOREWORD 7

1. Introduction to Underground Works 9

2. Hydro Tunnels 19

3. Railway Tunnels 107a. Railway Tunnels in Hilly Terrain 109b. Delhi Metro 120c. Kolkata Metro 125d. Konkan Railway 127

4. Road and Highway Tunnels 141

5. Water Supply and Irrigation Tunnels 149

6. Ancient Caves and Caverns 173

7. Future Tunneling and Underground Works 183

Page No.

HISTORY OF TUNNELS IN INDIA


Tunnels had their own roles toplay in every civilization and Indiancivilization is no exception. Tunnellingdates back to prehistoric times.Primitive people dug cavities orwidened the natural caves as shelteragainst weather, wild life and enemies.Archaeological research establishesthat man even in the stone-age

excavated cavities. Prehistoric tunnels built a fewthousand years ago have been discovered in India. Tunnelconstruction in India dates back to Mahabharata periodwhen Pandavas excavated an escape tunnel. History alsoreveals that many kings constructed escape tunnels fromtheir forts to safer places to be used during emergencies.

Modern tunnel construction in India has its originmainly in the nineteenth century when a number of railwaytunnels were constructed for the extension of the railwaynetwork for crossing hill ranges in Western Ghats,Vindhayas and in the foothills of Himalayas, for connectingfew hill resorts like Shimla. Barring a few tunnels in thesoft rock formations in the Himalayan foothills, most ofthe tunnels were excavated in hard rock strata inPeninsular India.

Construction of tunnels received a big boost afterIndependence when large programmes for harnessing ofwater resources were undertaken, which involvedconstruction of tunnels for water conveyance and otherunderground works. Tunnels in other sectors such asrailways, roads transport were also taken up. In the lastsix decades, about 350 tunnels have been constructedhaving a total length of about 660 km in various projects.

The Ministry of Power is according high priority forthe development of hydropower and has envisaged a visionPower for all by 2012. This enhanced capacity inhydropower sector is going to play an important role infulfilling this vision. It is proposed to add about 16,000 MWby the end of 11th Plan ending March 2012 and 30,000 MWby end of 12th Plan ending March 2017. Out of the installedcapacity assessed to be about 150,000 MW, only about23% of the vast hydro potential has been harnessed. Mostof the hydro potential is concentrated in the hilly states ofArunachal Pradesh, Sikkim, Himachal Pradesh,Uttarakhand and Jammu & Kashmir. Considerable tunnelingactivity is involved in the hydropower projects located inthese states. Execution of the tunnelling works is a bigchallenge in these areas, due to complex geological settingand difficult terrain conditions.

About 1200 km of tunneling is planned includinghydro sector in the coming years. Such development ofhydropower sector is opening avenues for construction oftunnels, underground caverns and other connectedinfrastructure on a very large scale.

FOREWORD Growth of road infrastructure is essential for thegrowth of road transport industry to facilitate smootherand faster movement of motor vehicles. India has about3.3 million kilometres road network which is the secondlargest in the world. It includes Expressways, NationalHighways, State Highways, Major District Roads andRural Roads. The total length of National Highways is66,600 km. This constitutes only 2 percent of the totalroad network but share approximately 40 percent of thetotal traffic on roads. The Government of India haslaunched a major initiative to upgrade and strengthenthe National Highways through various phases ofNational Highways Development Project which wouldnecessitate construction of tunnels in various reaches.

A national project to link Jammu with KashmirValley by 340 km broad gauge railway line has beenundertaken by the Ministry of Railways involvingconstruction of about 63 tunnels, out of which 21 havealready been completed in Jammu-Udhampur sector.On completion of this project, it will be an engineeringmarvel and will supplement the transportation needs andshall also encourage tourism and provide thrust toindustrial development of Jammu & Kashmir.

Delhi, the national capital with the population ofabout 16 million ought to have had a Rapid Mass TransitSystem (RMTS) network long back as per the prevailingstandards. Though late but its first phase covering 65.10km has already been completed and the work in phaseII (125 km) having a tunnel length of about 29 km is inprogress. Phase III & IV have been planned for extendingthe metro network work.

MRTS are also planned for other cities namelyBangalore, Hyderabad, Ahmedabad, Mumbai, Chennaietc. All these developments would involve extensiveconstruction activities of tunnels and underground works.Thus there is a great opportunity for all agencies in Indiaand abroad to get themselves actively involved in thedevelopment of tunnel industry in India.

This publication on History of Tunnels in Indiagives a glimpse of important features of well knowntunnels executed for various projects in different sectorssuch as Hydro, Railway, Road and Highways, WaterSupply and Irrigation and also ancient caves in India.

On behalf of Tunnelling Association of India,I sincerely thank all the organisations and individuals whohave provided information for compilation in the publication.

I am sure the information provided in this publicationwould be of great interest to all the readers.

V.K. Kanjlia

Secretary GeneralTunnelling Association of India and

Secretary, Central Board of Irrigation & Power

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INTRODUCTION TOUNDERGROUND WORKS

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India is a land of lofty mountains and mighty rivers.A vast land with such varied relief is inhabited by morethan one billion people. The country consists of threemain physical divisions. They are the great mountainsof the north and north- east, the great plains of northernIndia and the great southern plateau of Peninsular India.The southern plateau is flanked by the narrow coastalstrips which are a part and parcel of the peninsular landmass. India has diverse geology too.

Ancient CavesIndia has a very old history. Indus civilization is

well known. Tunnels had their own roles to play in everycivilization and Indian civilization is no exception.Tunneling dates back to prehistoric times. Primitivepeople dug cavities or widened the natural caves forshelter against weather, enemies and wild life.Archaeological research establishes that men even inthe stone age excavated cavities. Pre historic tunnelsbuilt a few thousand years ago have been discovered inIndia. Tunnel construction in India dates back toMahabharat period when Pandavas excavated escapetunnel . History also reveals that many kings gotconstructed escape tunnels from their forts to saferplaces to be used during emergencies. In India, numberof ancient caves are preserved even now and are wellknown through out the world. The paintings found inthese caves and the architecture of these caves whilereflecting the history of that period also indicates theirexpertise in excavating these caves. While the caves ofAjanta, Ellora, Elephanta are the tourist attraction, thereare other caves which are equally fascinating and detailsof such 18 caves are given in this book.

Tunnels are important components oftransportation networks, water conveyance networks andcommunication networks. They could be in rockyenvironment or in softer media and could be in variousgeometrical shapes depending on the functional utility.Earlier tunnels were constructed manually. Mansinsatiable passion to achieve more and more progressand production to meet the ever increasing requirementof mankind has driven him to design and improve uponthe production of basic tunneling tools into more efficientand productive ones.

Hydro TunnelsConstruction of tunnels received a big boost after

independence in 1947 when large programmes forexploitation of water resources were taken up whichinvolved construction of tunnels for water conveyanceand other underground works. In the last six decades

INTRODUCTION TOUNDERGROUNDWORKS

large number of tunnels have been constructed inconnection with multipurpose and hydroelectric projectsin the Himalayan region. Amongst the important projects,where tunnels have been built include Chamera, Baira-suil, and Nathpa Jhakri projects in Himachal Pradesh,Uri Stage-I, Dulhasti and, Salal projects in Jammu andKashmir, Dhauliganga project in Uttaranchal. In the North-East, important tunnel jobs have been executed at Loktakand Teesta stage- V Projects. In the Peninsular Indiatoo, there was spurt in tunneling activity connected withthe execution of Koyna, Nagarjunasagar, and Srisailamprojects. Tunnels with bore diameter of as much as 9 mand length up to over 25 km at Beas - Sutlej Link havebeen built in this period.

About 344 hydro-tunnels, small and big, totalinga length of about 659 km. have already been completedwhile 126 tunnels having a length of about 220 km. areunder construction. About 567 tunnels having a totallength of about 1200 km are planned to be executed inrecent future. Details of these projects are indicated inthe chapter on Hydro Tunnels Total lengths of tunnelsin some projects are indicated in the table below.

Name of HE Project Length of tunnelsincluding adits (km.)

Teesta Project 22.57

Tehari Project 17.32

Baira Suil Project 16.39

Chamera I Project 10.72

Nathpa Jhakri Project 90.17

Uri Project 19.40

Koyna Project 11.335

Kalinadi Project 17.21

Railway TunnelsApart from tunnels for hydroelectric works, another

sector where tunnels have a important role to play isRailway including Metros. Modern tunnel constructionin India has its origin mainly in the Nineteenth centurywhen a number of railway tunnels were constructed forextension of the rail network for crossing hill ranges inWestern Ghats, Vindhayas and in the foothills ofHimalayas for connecting few hill resorts like Shimla.Some of the Hill trains connecting important hill stationspassing through number of tunnels have historicalimportance and some of them have been given WorldHeritage Status by UNESCO. The hill train running onKalka Shimla section, built during the period 1900-1903 has to pass through 107 tunnels of varying lengths.The longest tunnel, the Barog Tunnel is 1146m long.The expertise and equipments available at that time incomparison to what we have today clearly reflects thedifficulties which must have been faced at that period toconstruct these memorable tunnels.

The new railway line, prestigious and the mostchallenging Jammu-Udhampur-Srinagar-Baramulla

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10.15 m dia Tunnel Junction (Square) for Nathpa Jhakri Project, Himachal Pradesh

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(340km.) under construction in the Himalayan Mountainsin Jammu and Kashmir state passes through difficultterrain. The adverse geology enroute has led to increasein tunnel length because it was not possible to locatebridges and tunnel portals in slide zones and otherunfavorable locations. The rocks range from looseconglomerates and severly folded and crushed sand-clay- silt stones in Katra- Sangaldan region to slates,schist and phylites beyond Sangaldan. The line shall cutacross three major thrust zones, the Reasi thrust, theMuree thrust and the Pir Panjal thrust. The rocks alongthe proposed alignment are heavily folded, over thrustedand faulted at many places making the rocks highlyjointed and crushed.

There are 63 tunnels having a total length of about120 km. along the alignment, the longest being 6.574km. Jammu-Udhampur Rail Link (53.4 km) forms a partof the Jammu-Udhampur-Srinagar Baramulla railway lineconnecting Jammu, the summer capital of the J&K Statewith Udhampur the district headquarter. Track traversesthe domain of Shiwalik ranges of young Himalayas whichis highly undulating and difficult hilly terrain. Constructionof railway line involved 85.22 lac cum of earthwork androck cutting; 21 tunnels with total length of 10.680 kms,longest tunnel being 2.445 km and 158 bridges with spansup to 102 m ( in prestressed concrete) and 154 m (insteel) and pier heights up to 68 m above bed. IndianRailways, with a rich history in tunneling since 1889 whenfirst tunnel commenced at Bhor Ghat, have conqueredthe mighty and unpredictable Himalayas on JURL(Jammu-Udhampur Rail Link) with Broad Gauge line.Upon completion of the entire project, it will be anengineering marvel and will supplement thetransportation needs and shall also encourage tourism,and provide thrust to industrial development. Inadequateknowledge of strata in Himalayas makes tunneling anextremely complex, arduous, and hazardous andpainfully slow work. Certain problems were also facedwhile implementing this project. Besides the details ofthese two hilly rail links details of Kangra Valley Railway,Nilgiri Mountain Railway and Neral- Matheran Toy trainare given in the chapter on Railway Tunnels in HillyTerrain.

Another important railway tunnels belong toKonkan railway. Konkan is a thin strip of land, about 50to100 km. at its widest 720 km long between the ArabianSea and the Western Ghats or the Sahyadri mountainranges. Its proximity to the Arabian Sea, especially thefact that several major and minor sea ports in peninsularIndia fall in this region, has endowed Konkan with a richhistory and cultural heritage.

Konkan was also the area where Vasco De Gamafrom Portugal landed in 1498, leading a Europeanonslaught that eventually led to the colonisation of India.

The history of the Konkan Railway goes backmore than 150 years. Ever since 1853, when the railwaysbegan in the sub-continent, the people of the regionwere keen to have a railway line for efficient anddependable transportation of goods and passengers. Fordecades, the only means of transport here was the sea,

and this route was severely limited by the fact that it couldnot be used during the monsoon. The roads connectingcoastal towns came up only recently. The area, therefore,remained largely undeveloped, though it was rich in naturalresources.

Only after the Konkan Railway CorporationLimited (KRCL) came into existence as a public limitedcompany in July 1990 the work started on this projectand finally commissioned on 26-01-1998.

In the 760 km. long stretch of railway line, thereare 92 tunnels aggregating to a total length of 83.6 km.and nine tunnels out of these were longer than two km.It was for the very first time that such massive tunnelingwork was attempted for vehicular tunnels in India. Outof these, 74 km was through hard rock, 8.4 km. throughsoft soil, and the balances 1.2 km through cut and coverconstruction.

In the field of development of metros, though abeginning was made long back in the year 1974 whenthe work on Kolkata metros started and subsequentlycompleted in the year 1995, the work on Delhi metrostarted only in the year 1995. .

Metro Railway construction in Kolkata is firstattempt of underground railway construction in India andalso in one of the busiest cities, having poor soilconditions. For this project, a unique cut and covermethod of construction was used even through the verybusy roads of Kolkata, except in small stretches, whereshield tunneling was adopted. Cut & Cover method ofconstruction was primarily adopted due to economicalconsideration.

Kolkata Metro Railway is successfully runningbetween Tollygunge & DumDum. Success has furtherencouraged for further spread of a stretch of 18.65 km.between New Das Nagar- Salt Lake City Sec- V , whichis being planned and detailed project report has beenprepared.

Another hall mark is the Delhi Metro. The city ofDelhi with a population of around 16.0 million shouldhave had an Mass Rapid Transit System (MRTS)network long back, whereas actually it is still 65.10 kmsat the take-off stage.

Delhi has experienced phenomenal growth inpopulation in the last few decades. Its population hasincreased from 57 lakhs in 1981 to 162 lakhs in 2006and is poised to reach 190 lakhs by the year 2011. Forwant of an efficient mass transport system, the numberof motor vehicles has increased from 5.4 lakhs in 1981to 51 lakhs in 2007 and is increasing at the rate of 6.21lakhs per annum. The result is extreme congestion onDelhi roads, ever slowing speeds, increase in roadaccidents, fuel wastage and environmental pollution withmotorized vehicles alone contributing to about two thirdsof the atmospheric pollution.

Government of India ( GOI) and the Governmentof National Capital Territory of Delhi (GNCTD) , in equalpartnership, have set up a company named Delhi MetroRail Corporation Ltd. in the year 1995 which has already

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Underground Excavation in Inclined Pressure Shaft (3.1 m dia) for Baspa-II Project in Himachal Pradesh

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commissioned a 65.10 kms route in Phase-I and isproceeding ahead with another 125 kms in Phase - II.Phase II work is to be completed by 2010 before theCommon wealth games. The work is going on warfooting. Phase III and Phase IV covering length of about112 km and 109 km respectively are also envisaged infuture and these Phases are likely to be completed by2021 and total network of metro rail in Delhi would beabout 414 km.

Roads & Highway TunnelsGood and short highways help in efficient

transportation. In this category, Rohtang tunnel is ofrelevance. This tunnel is a long cherished dream for theinhabitants of Lahaul and Spiti, Pangi valley and Kazadistrict of Himachal Pradesh and Ladakh region ofJammu & Kashmir State.

Keeping in view the strategic importance and socioeconomic need of region, the responsibility fordeveloping surface communication network for this partof Indian Sub-Continent ( J&K State & mountainous regionof Himachal Pradesh) was assigned to Border RoadOrganization (BRO) in 1960 by Govt. of India.

The work on 8.8 km long Rohtang Passtunnel costing Rs 17 billion, aimed to provide an all-weather alternative route to Leh-Ladakh region, besidesHimachals snow-bound tribal district of Lahaul and Spiti,will commence this year-end. Because of heavy snowat higher reaches of Rohtang pass during winter, theroad connectivity for Lahaul and Spiti and Leh fromHimachal Pradesh remains disrupted for almost four tofive months. The snowfall is heaviest at the 3980 m-high Rohtang Pass. This tunnel will be built below thepass so that it avoids the heavy snow and provides allweather road, besides reducing the distance by 44kilometre. The BRO has planned to use latest tunnelboring machines and engage best companies of theworld for the tunnel work.

Another important highway having number oftunnels is the National Highway NH-4 which connectsMumbai earlier known as Bombay with the city ofBangalore via Poona (Pune). This is a very old roadconstructed during British era. The road betweenMumbai & Pune is passing through precipitous mountainranges of Sahyadri hills; the famous Khandala Hill stationis around midway enroute.

Due to increase in the traffic every year resultingin jams, accidents, increase in travel time etc, it wasnecessary to build a new and independent expressway.

Government of Maharashtra planned a newExpressway by-passing the city of Panvel in Raigaddistrict upto outskirt of Pune city in 1990. In order toease out the alignment and reduce the steep gradientat few locations of the road in the hilly terrain, provisionof the tunnels was unavoidable. Therefore, twin tubetunnels have been constructed at five locations i.e.Bhatan, Madap, Khandala, Kamshet I and Kamshet IIand one single tube tunnel at Adoshi for Mumbai boundtraffic. Size of each tunnel is 17.6 m wide, 9.8 high, to

accommodate four lanes of traffic. Cross-sectional areaof each tunnel is varying between 148 m to 157 m,which is considered to be a very large section,constructed for the first time in India for any road project.The length of the tunnels varies between 168 m to1086 m, totaling to 5762 m.

The tunnels on this expressway have been providedwith modern facilities of ventilation, lighting,communication system, fire fighting vehicles,computerized control room etc; and would rank amongstthe best in the world.

Water Supply TunnelsWater supply tunnels have predominantly been

used in India in the state of Maharashtra that inMumbai.Municipal Corporation of Brihan (MCBM).Mumbai has used tunnels in number of its WaterSupply Schemes. The first such scheme was VaitarnaScheme where 7.2 km. long tunnel was driven throughVaitarna hills to link the Vaitarna and Tanasa lakes in theyear 1952. Since then tunnels have always remainedan undivided part of any water supply scheme of MCBM.The tunneling system adopted in Mumbais water supplycomprises an inlet and outlet shafts, vertical in naturewith intermediate shafts, if any, as per the requirements.TBMSs have been used for drilling of tunnels. In factMCBM has been the pioneer with regard to adoption ofTBMs for tunnel construction. Since then MCBM hascompleted more than 25 km of tunneling for water supplyin Mumbai and about 29 km are under construction today.The range of diameters of tunnels varies from 2.2m to3.5 m. The details of these projects and another projectMorbe Dam Project are given in the relevant Chapter.

Though predominantly irrigation channels areconstructed for irrigation purposes, even then some tunnelshave been constructed for irrigation purposes in differentparts of India, totaling a length of about72 km. Some of the important irrigation tunnels pertain tothe projects- Tawa project, Hemavaty reservoir project,Malaprabha Irrigation Project and Ghatprabha project.Details of a recently constructed irrigation tunnel called Punasa Tunnel diverting water of Narmada river from thereservoir of Indira Sagar Project are highlighted in this book.

Construction TechnologyA review of tunneling methods in India shows that

the conventional drill-&-blast method remains practicallythe dominant practice for excavation of tunnel in India..

Construction EquipmentsAttempts have been made in the past on some

projects to use Roadheaders and Tunnel BoringMachines (TBMs) with success in some and failure inothers. A beginning was made using the TBMs for theconstruction of a water supply tunnel in Bombay calledthe Malabar Hill Tunnel and Dulhasti Project in J&K. andParbati Project Stage II in Himachal Pradesh. Roadheaders are being used for quite sometime in the miningsector particularly in the Singareni Collieries Co. Ltd. Aroad header was used for the excavation of the Loktaktunnel in Manipur in late Seventies.

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Till recently, barring a few cases, the use of steelribs with backfilling by tunnel muck or lean concrete waspractically the only method of supporting in India. Thisbeing a passive support system, a considerable damageis done to the rock mass before the ribs interact with it.The combination of the drill-&-blast method of excavationand steel rib support system delays the supporting action,allows opening of the existing joints, creates new fractures,permits loosening of the rock mass in the roof, mobilizeshigher tunnel closures and greater rock loads which requirelarger excavation and thicker support. All these problemsresult in increased cost and completion period.

Lately, there has been considerable increase inthe use of shotcrete as a support system, particularly forlarge underground cavities. The use of steel fibre reinforcedshotcrete (SFRS) has also been made at a few projects,such as, Uri (J & K) and Koyna Project (Maharashtra).

Compared with the great advances made inmethodology for tunnelling all around the globe, it isobvious that we have still a long way to go to catch upwith modern tunnel construction technologies. With newtunnelling techniques, extensive developments have takenplace in the field of special excavation equipment -hydraulic jumbos, Tunnel Borers, Road Headers,explosives, methods of ground stabilization, methods forrock support, special equipment for concrete lining, whichenable realization of tunnel construction at rates hithertounimaginable.

Construction industry in India is growing at a fasterpace. About 1200 km of tunnels including adits areproposed to be constructed for number of projects whichare planned to be taken up in near future. Keeping inview the execution of large number of projects foraccelerated development of tunnel projects, sufficient andcompetent agencies are not available in the country. Toenable more construction companies to enter in the field,policies and procedures have been simplified byGovernment of India. With the change in policies andprocedures, some international reputed companies havealready started operation in India in the recent past andmany more are expected to join shortly.

Geological InvestigationAlmost every aspect of a tunneling project, from

its conception to commissioning, is influenced by thegeology of the area. Reliability of the predicted geology,therefore, plays an important role in the success of theproject. Inadequate geological investigation and pooranticipation of the nature and the magnitude of problemscatch the tunneling engineers unawares, resulting indelays and higher cost of construction. Inadequateinvestigations could be attributed to financial, technicaland site constraints etc .

The nature of major construction problems whichhave been experienced in the past due to inadequateinvestigations are:

(i) Buckling of steel ribs requiring rectification undersqueezing ground conditions in lower Himalaya.

(ii) Roof falls and chimney formations

(iii) Water inrush (Chhibro-Khodri tunnel)

(iv) Methane explosion (Giri-Bata tunnel, Loktak tunnel)

(v) Running ground conditions

In view of the above, adequate investigationsneeds no emphasis. Keeping in mind that huge tunnelingactivity is likely to be involved while executing manyproposed hydroelectric, railway, and road projects inHimalayan region where challenges are more, attemptsare being made to induct modern techniques ofengineering geological investigations in order to unravelgeological complexities and adversities well in advance,so that geological surprises are minimized duringconstruction. The other means of investigations suchas satellite image analysis and geophysical methodsneed to be explored. Geological investigations and thesemethods of investigations could definitely provideadditional information which shall be useful during boringof tunnels. Besides, numerical modelling for designconsiderations and fast tunneling technology usingTunnel Boring Machine (TBM) are being adopted toreduce time and cost over run and ensure safety andstability of the structures.

Contractual PracticesFor successful and timely completion of a tunnel

project, correct contracting practices are very important.Essential contracting practices include all operations andprocedures involved from fixing up an agency forexecution of the work, getting a contract agreementsigned and effective follow up and monitoring theprogress of works till completion of the job.

Practically, all the tunneling projects in the countryare executed through contractors only and it has beenexperienced that there are invariably time and/or costoverruns on almost every such project due, among otherthings, to deficiencies in the contracting practices whichare generally found to be indifferent to the project needs.Inadequate finances, delay in decision making,inadequate geological exploration often lead tocontractual problems

Future of Underground Construction in IndiaFor a fast developing country like India, a need

has been felt to enhance the electrical power, a basicnecessity for any developmental activity. Existing electricalpower being considered insufficient for the requirementfor the country, it is now envisaged to provide Power forall by 2012 and big plans to achieve this target are onthe anvil. Hydro power addition is expected to play animportant role in this vision. Not only in 11th five year planbut also in the 12th five year plan ending March 2017,hydro power development has been emphasized. It isproposed to add about 16000 MW hydropower by end of11th plan ending 2012 and 30000 MW by end of 12th planending 2017 and such development have opened avenuesfor construction of tunnels, under ground caverns etc. andother connected infra structure on a much larger scale.

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Considerable activities in the field of tunneling are thereforeenvisaged for the execution of water resources projectsfor irrigation, hydropower generation, building of roads inmountainous area, subsurface excavation for undergroundrailway and for mining purposes. With the growing needto accelerate the tempo of water resources andhydropower development, new projects are being takenup, which involve construction of about 1200 km length oftunnels, practically in every type of strata and sizes varyingfrom 2.5 m dia to 14 m dia besides underground excavationof caverns for the power houses. These projects areplanned to be taken-up on priority for completion of someby end of 2012 and others by end of 2017. It is alsoplanned to develop 31000 MW in the 13th planning ending2022 and remaining about 36500 MW by end of 14th planending 2027. These developments would provide amplescope for tunnel and underground construction in a bigway in times to come.

Construction of Metro is another field where lot ofactivity in tunnel construction and underground works areenvisaged in times to come. After completion of ongoingtunneling works of about 29 km in phase- II, Delhi MetroRail Corporation is planning to take up phase-III andphase-IV involving extension of metro track by about 113km. and 109 km. respectively thereby extending the trackto a length of about 414 km. These developments wouldalso involve construction of tunnels and also undergroundstations in a big way.

The success of the Delhi Metro has encouragedother Indian cities to seriously attempt to introduce Metrosystems. DMRC has already been appointed the PrimeConsultant for Hyderabad and Kochi Metro and is the in-house consultant for Mumbai Metro. DMRC has alsosubmitted Detailed Project Reports (DPRs) for Metrosystems in Bangalore, Kolkata (East-West Line),Mumbai, Ahmedabad and Chennai. DPRs are beingprepared for Pune and Ludhiana. In fact, work has alreadybegun on the Bangalore and Hyderabad Metros.

Details of the other Metros being planned in Indiaare as follows:

Sl. Name of Line KmsNo. the city1 Bangalore Line-I Mysore Road 18.1

Baiyyappanhalli

Line- II Yeshwantpur 14.9Jaya Nagar Airport Link

City Airport Terminalat Police Ground

(NH-7) New 33.65InternationalAirport (Phase-I)

2 Hyderabad Line-I Miyapur 26.27Chaitanya Puri

Line-II Secunderabad 13.18Falaknuma

Line-III Tarnaka 21.74Hi tech City

Airport Link

Begampet Airport -Hyderabad

International Airport at 42.35

Shamsabad (Phase-I)

3 Ahmedabad Metro System

Line-I Akshardham 32.65APMC Vasana

Line-II Ahmedabad 10.90Thaltej

Regional Rail System

Line-I Barjedi 44.85Ahmedabad Kalol

Line-II Ahmedabad 9.85Naroda

4 Mumbai Line-I Versova 11.07AndheriGhatkopar

Line-II Colaba 38.24Bandra Charkop

Line-III Bandra Kurla 13.18Mankhurd

5 Kochi Line-I Alwaye Petta 25.25

6 Chennai Line-I Airport 23.05Wahsermen Pet

Line-II Chennai Fort - St. 23.44Thomas Mount.

7 Kolkata New Das Nagar Salt 18.65Lake-City Sec - V

8 Ghaziabad Dilshad Garden 9.41New Bus depot

9 Badarpur Badarpur - YMCA Chowk 13.87

Metros which has wide scope for the constructionof tunnels and underground works have an excellent futurein India in view of the large scale aforementioned workswhich are planned.

In addition road tunnels also are to be executed infuture. The work of Rs 17 billion Rohtang Tunnel project,aimed to provide an all-weather alternative route to Leh-Ladakh region, besides Himachals snow-bound tribaldistrict of Lahaul and Spiti, will commence this year-end.Because of heavy snow at higher reaches of Rohtangpass during winter, the road connectivity for Lahaul andSpiti and Leh from Himachal Pradesh remains disruptedfor almost four to five months. This tunnel will be builtbelow the pass so that it avoids the heavy snow andprovides all weather road, besides reducing the distanceby 44 kilometre. Border Road Organisation has gearedup to take up this work. The tunnel is likely to be completedby 2014. There are other road tunnels , the execution ofwhich are under active consideration.

1818


An important rail tunnel work is going on Jammu-Udhampur- Srinagar- Baramulla sector in the state ofJammu and Kashmir. The Jammu- Udhampur sectorhaving 21 tunnels has already been completed while thework in the remaining sector having 42 tunnels with totallength of 108 km. is in progress. In other sectors alsothere is a good future role for underground works.

Tunnels are generally located in difficultenvironments- in various types of softer media- and thealignment may traverse zones of various complexities. Itis important that such engineering projects are properlyconceptualized and planned systematically to ensuresmooth implementation. Since one of the fundamentalmeasures to ensure fast track construction is the choiceof a safe alignment, careful consideration is required to

be given to avoid all types of hazards as far as possibleand these include treacherous soil conditions,subterranean water streams, strata bearing hazardousgases such as methane, etc. In addition, it is also to beensured that adequate investigations have been done,proper selection of tunneling equipment has been made,appropriate contracting practices are available,environment and forest clearances have been taken,competent construction agencies are available, socialissues have been taken care of and similar other issuesare duly considered. If these are not properly accounted,the implementation will not be smooth and many problemsare likely to arise from various affected agencies duringthe construction leaving to delay and cost over-runs.

1919


HYDRO TUNNELS

2020


2121


HYDRO TUNNELS

For a fast developing country like India, a needhas been felt to enhance the power generation, a basicnecessity for any developmental activity. Existingelectrical power is considered insufficient for therequirement of the country. Significant portion of ourpopulation is deprived of electricity. It is now envisagedto provide Power for all by 2012 and big plans toachieve this target are on the anvil. Hydropower additionis expected to play an important role in this vision. Sincepresent installed capacity of hydropower plants is onlyabout 36,000 MW against hydropower potential of about1,50,000 MW, there is a big scope for exploitation ofbalance hydropower potential. Not only in 11th five yearplan but also in the 12th five year plan ending March2017, hydropower development has been emphasized.It is proposed to add about 16,000 MW hydropower byend of 11th plan and 30,000 MW by end of 12th plan.Such developments have opened avenues forconstruction of tunnels, underground caverns and otherconnected infra structure on a much larger scale.

Construction of tunnels received a big boost afterindependence in 1947 when large programs forexploitation of water resources were taken up whichinvolved construction of tunnels for water conveyanceand other underground works. In the last six decadeslarge number of tunnels have been constructed inconnection with multipurpose and hydroelectric projectsin the Himalayan region. Amongst the important projects,where tunnels have been built include Chamera, Baira-Siul, and Nathpa Jhakri projects in Himachal Pradesh,Uri Stage-I, Dulhasti and Salal projects in Jammu andKashmir, Dhauliganga project in Uttaranchal. In theNorth-East, important tunnel jobs have been executedat Loktak and Teesta Stage-V Projects. In the PeninsularIndia too, there was spurt in tunnelling activity connectedwith the execution of Koyna, Nagarjunasagar, andSirisailam projects.

In India, considerable tunnelling activity is involvedin the hydropower projects located in Himalayan regionand it is bound to be accelerated since, of late, majorthrust has been laid by the Government of India for

harnessing available hydropower potential of theHimalayan rivers in order to strike a balance betweentotal demand and supply in the power sector. Himalayanregion occupies a unique position having substantialhydropower potential. Out of the total 1,50,000 MWhydropower potential in India, major share lies in theHimalayan rivers constituting about 73% of the totalpotential, that comes to about 1,10,000 MW. Presentlyonly about 9400 MW hydropower has been developedin Himalayan sector and a vast potential remainsunutilized. The pace of hydropower development inHimalayan region is facing many challenges related tocomplex geological setup, difficult terrain conditions andhigh seismicity. Besides, adverse climatic conditions,forest and environmental issues and rehabilitationproblems are some more hurdles. In order to achievean ideal hydro-thermal mix, serious efforts are being putby the Government of India to focus on harnessing ofhydropower potential of Himalayan rivers in Uttaranchal,Himachal Pradesh, Jammu & Kashmir and the north-eastern states where about 527 hydel projects (413 runof the river and 114 storage schemes) have beenidentified.

Construction of these hydel projects will involveextensive tunnelling, particularly in the run of the riverschemes where length of power tunnels is in kilometreslike in Nathpa Jhakri Hydel Project in the state ofHimachal Pradesh where the length of the headracetunnel is 27.4 km. In the state of Uttaranchal alone about750 km tunneling will be involved in different hydroelectricprojects already proposed.

Many organizations such as National HydroelectricPower Corporation (NHPC) Satluj Jal Vidyut Nigam Ltd.( SJVNL), Tehri Hydro Development Corporation (THDC),North Eastern Electric Power Corporation (NEEPCO),Narmada Hydro Development Corporation (NHDC), ,Uttaranchal Jal Vidyut Nigam, NTPC Ltd., StateGovernments, Joint Ventures and some privateorganizations are actively involved in development of hydropower projects in the country which involve both theconstruction of tunnels and underground works. About659 km. of tunnel including HRT,TRT, adits etc. of varioushydroelectric projects have been completed. Of thesecompleted tunnels, about 347 km. tunnel pertain toprojects owned by state governments, 173km. by centralGovernment, 123 km. by Joint ventures and 16km. byPrivate sector. 220 km. of tunnels are also underconstruction in different hydroelectric projects. Followingtable gives the lengths of tunnels including adits forcompleted and under construction hydroelectric projects.

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Roof Support of Underground Power House Cavern for Lakhwar Project (Uttaranchal)

2323


Sl. Name of the Project Length in kmNo.

A Completed

1 Nagarjuna sagar Project (960 MW) 6.467

2 Srisailam Left Bank HE Project 4.842(1670 MW)

3 Lower Sileru (460 MW) 3.206

4 Neelam Sanjeeva Reddy Sagar 1.771Project

5 Ranganadi HE Project (405 MW) 10.264

6 Karbi Langpi HE Project (100 MW) 4.43

7 Dalaima Small Hydro Electric (4 MW) 1.77

8 Kopili HEP 1st Stage (275 MW) 9.659

9 Sardar Sarovar (Narmada) Project. 1.74(250 MW)

10 Sardar Sarovar Narmada Project, 1.83Power House (1200 MW)

11 Sanjay Vidyut Pariyojna - (120 MW) 11.099

12 Shanan Hydel Project (110 MW) 4.673

13 Baira Siul Power Station (180 MW) 16.319

14 Chamera-I (540 MW) 10.72

15 Chamera-II (300MW) 16.906

16 Beas Sutlej Link Project 25.46(BSL) Dehar HEP (990 MW)

17 Beas Sutlej Link Project 5.017Pong HEP (396 MW)

18 Nathpa Jhakri HE Project (1500 MW) 90.172

19 Baspa Hydroelectrci Project (300 MW) 7.695

20 Uri Stage - I (480 MW) 19.394

21 Dulhasti (390 MW) 11.495

22 Salal (690 MW) 5.454

23 Subarnarekha Hydel Project (130 MW) 1.706

24 Maithon Hydel Project (60 MW) 0.0635

25 Sharavathy Valley HEP (1006.2 MW) 6.1

26 Kali Nadi HEP Stage I (855 MW) 17.21

27 Varahi HEP (230 MW) 3.05

28 Sabarigiri Hydro Electric Project 7.708(300 MW)

29 Idukki HE Project (780 MW) 9.932

30 Idamalayar Multipurpose Project 1.598(75 MW)

31 Kakkad Hydro Electric Project 10.548(50 MW)

32 Lower Periyar HEP(180 MW) 17.611

33 Kuttiyadi Hydro Electric Project 0.919(125 MW)


34 Pallivasal HEP (67.5 MW) 3.119

35 Poringalkuthu HE Scheme (32 MW) 1.228

36 Neriamangalam HEP (45 MW) 3.395

37 Sengulam Hydro Electric Project 1.779(48 MW)

38 Panniar Hydro Electric Project 2.93(30 MW)

39 Sholayar (54 MW) 0.771

40 Koyna HEP Stage I,II & III (920 MW) 11.335

41 Koyna HEP Stage IV (1000 MW) 17.747

42 Tillari Hydro Electric Project (60 MW) 3.968

43 Bhira Hydro Electric Project (300 MW) 8.615

44 Bhandaradara Project ( 44 MW) .208

45 Vaitarna HEP (60 MW) 3.299

46 Ghatghar PSS (250 MW) 4.44

47 Lokatak HE Project (105 MW) 6.766

48 Umiam Umtu Stage I (36 MW) 2.058

49 Umiam Umtu Stage II (60 MW) 0.019

50 Umiam Umtu Stage III (18 MW) 3.441

51 Umiam Umtu Stage IV (11.2 MW) 7.637

52 Bansagar Tons Multi-purpose 3.928Project (425 MW)

53 Indira Sagar Project (1000 MW) 4.11

54 Doyang Hydro Electric Plant 10.61(75 MW)

55 Balimela Hydroelectric Project 5.648(360MW)

56 Upper Kolab Hydro Electric 0.392Project (320MW)

57 Upper Indravati (600 MW) 13.921

58 Bhakra Dam (1325MW) 0.805

59 Rangit Sagar Dam (600 MW) 3.42

60 Jawahar Sagar (99 MW) 0.412

61 Rana Pratap Sagar (172 MW) 1.467

62 Rangit (60 MW) 5.411

63 Teesta-V (510 MW) 22.576

64 Kodayar Hydro Electric Project 6.16(100MW)

65 Periyar Hydro Electric Project 3.103(40MW)

66 Mettur Hydro Electric Project 0.776(200MW)

67 Kundah Hydro Electric Project 8.165(500MW)

2424



68 Sarkarpatti (30MW) 3.85

69 Sholayar (95MW) 3.655

70 Kadamparai Pumped Storage 4.147Project (400MW)

71 Madras Atomic Power Station 4.78

72 Parsons Valley Hydro Power Station 3.055(30MW)

73 Pyakara Hydro Power Station 11.973(251.91MW)

74 Maneri Bhali Hydroelectric Project 8.467(90MW)

75 Tehri Hydro Electric Project 17.329(1000MW)

76 Dhauliganga H.E. Project, Stage-I 9.124(280MW)

77 Vishnu Prayag Hydroelectric Project 22.83(400MW)

78 Rammam Hydel Project, Stage 3.25II (50 MW)

Sub Total 648.279


B Under Construction

1 Kameng HE Project (600 MW) 18.261

2 Subansiri Lower Project (2000 MW) 13.512

3 Chamera-III (231 MW) 24.788

4 ParbatiStage-II (800 MW) 44.419

5 ParbatiStage-III (520 MW) 14.475

6 Rampur Hydro-electric Project 19.071(412 MW)

7 Baglihar Project - I (450 MW 10.324

8 Uri - II (240 MW) 12.039

9 Chutak HE Project (44 MW) 5.420

10 Myntdu Stage - I (84 MW) 3.316

11 Tons Hydel Project (Tunnel- II) 4.569

12 Sewa-II (120 MW) 14.77

13 Loharinag Pala HEPP (600 MW 22.667

14 Loharinag Pala HEPP (600 MW) 12.801

Sub Total 220.432

As is evident from the above table, 1196 km oftunnel is planned to be constructed in near future besidesother underground structures and in view of such largetunnelling works to be under taken, there is a vast scopefor agencies within as well as outside the country, todemonstrate their capability either in providing servicesor equipment.

A review of tunneling methods in India shows thatthe conventional drill-&-blast method remains practicallythe dominant practice for excavation of tunnels in India.Attempts have been made in the past on some projectsto use Roadheaders and Tunnel Boring Machines(TBMs) with success in some and failure in others. Abeginning was made using the TBMs for constructionof a water supply tunnel in Bombay called the MalabarHill Tunnel and Dulhasti Project in J&K. and ParbatiProject StageII in H.P. To have good progress intunneling, there is need to use mechanized tunnelingmethods and latest tunnelling techniques. Till recently,barring a few cases, the use of steel ribs with backfillingby tunnel muck or lean concrete was practically the onlymethod of supporting in India. This being a passive

support system, a considerable damage is done to therock mass before the ribs interact with it. Thecombination of the drill-&-blast method of excavation andsteel rib support system delays the supporting action,allows opening of the existing joints, creates newfractures, permits loosening of the rock mass in the roof,mobilizes higher tunnel closures and greater rock loadswhich require larger excavation and thicker support. Allthese problems result in increased cost and completionperiod.

Lately, there has been considerable increase inthe use of shotcrete as a support system, particularlyfor large underground cavities. The use of steel fibrereinforced shotcrete (SFRS) has also been made at afew projects, such as, Uri (J&K) and Koyna Project(Maharashtra).

A brief description of the salient features ofimportant projects along with geological set up,construction methodology, problems encountered andremedial measures adopted for tunnels and undergroundworks are given in the subsequent pages.

2525


Tunnelling dates back to pre-historic time. Primitiveman made cavities or found natural caves for their dwelling.Tunnel construction in India dates back to Mahabharataperiod when Pandvas constructed escape tunnel. Historyreveals that many kings got constructed the escapetunnels from their fort to safer places to be used duringemergencies. The caves of Ajanta, Ellora and Elephantaare excellent examples of architecture and undergroundspace development. Earlier tunnels were excavated withmanual methods, today it is state-of-the-art technology.Major improvement in the methodology of tunnelexcavation has been made world over due to technologicaladvancement. Today tunnels are being constructed withmodern equipment and methodology.The tunnelconstruction involves huge investment and had a directimpact on the completion schedule and milestones ofthe project. Todays trend demand for competency toforecast the tunnelling condition, more mechanizedapproach and utilization of state of the art technology toachieve faster rate in construction by tackling the pitfallseffectively. For sustainable development, application ofnew technologies and use of sophisticated equipmentsare the need of the day to execute the undergroundstructures in a cost effective manner.

There are three major areas of tunnels andunderground cavern construction;

. For hydro power, water supply, sewerage andirrigation

TUNNELLING ANDUNDERGROUNDWORKS IN INDIA

For vehicular traffic and transportation of goods i.e.,for railways and road tunnels

For defence and nuclear purposes- undergroundstorage etc.

Modern tunnel construction in India has its originin nineteenth century when a number of railway tunnelswere constructed for extension of rail net work in variouspart of the country for crossing of hill ranges. The famousKalka-Simla railway track passing across 102 tunnelsand Siliguri-Darjeeling rail network are beautiful examplesof tunneling activity in foothill Himalayas. The Konkanrailway is a shining example of tunneling through WesternGhats in peninsular India. Kolkata metro and Delhi Metroare the glorious example of advancement of technologyin the field of underground tunneling. The proposed 190km long Jammu-Udhampur-Katra-Quazigund-Baramullarailway track passes through very rugged terraincomprising soft rocks of Shiwaliks, rocks of lesserHimalayas and many regional thrust, has been partlycompleted in challenging geological conditions.

Construction of hydro power tunnels received a bigboost soon after India independence in 1947 whenambitious plans for harnessing the hydro power potentialwere launched which involved construction of tunnels forconducting water and other underground works. In thelast six decades a number of hydropower projects havebeen constructed in Himalayan region as well as inpeninsular region. Apart from tunnels for hydroelectricprojects, few tunnels were constructed for transportationand water supply works, the notable among them areBanihal road tunnel across the Pir Panjal range in Jammu& Kashmir and Mumbai water supply works. The work onmuch awaited Rohtang tunnel involving an all weatherpassage between snow clad regions of Himachal Pradeshand Laddakh region of J&K is on the anvil.

2626


HYDRO POWERTUNNELS

Hydro power projects have a very important role tomeet the ever growing demand of energy .An ambitiousprogramme of 50,000 MW capacity addition has beenlaunched by Govt.of India targeting to harness theavailable hydro power resources and to provide power toall by 2012. In India, about 73 % of the total power potentialof the country lies in Himalayas. However, hydropowerdevelopment in Himalayas is faced with many challengesrelated to complex geological set up, difficult terrainconditions and high seismicity. Some of the commonproblems faced during construction are water bearingzones, stresses due to high cover, squeezing groundcondition etc. These adverse situations can be handledby adequate investigation prior to construction, planningsuitable construction methodologies depending upon thenature of rock, designing of adequate support, properdrainage arrangement and monitoring of deformations, ifany, through instrumentation. Certain pre-constructionmeasures such as advance probe drilling and pre-groutingin water bearing strata are very useful in forecasting thetunneling conditions and making proper arrangements inadvance to tackle the difficult zones. More recently theTunnel Seismic profiling (TSP) technique has also beenintroduced to predict the sheared and water bearing stratawell in advance.

Advancement in construction methodology hasalso given boost for tunneling at a faster pace. Till recentlyin India, drill and blast was the conventional method fortunneling by which the progress was slow. Attempts havebeen made to deploy Tunnel Boring Machine (TBM) insome of the projects, though with partial success.However, the TBM are successful in underground metroworks where the strata are mostly homogeneous.Advancement has also come in the field of rock support.Normally, conventional steel support backfilled withconcrete are installed in weak rock. The installation ofribs is a time taking job and do not support the rock massimmediately, as a result the ribs often gets deformed andtheir rehabilitation is a cumbersome process which mayresults in the time and cost overrun. Introduction of piperoofing, double wire mesh with fibre reinforced shotcreteand lattice girders are found to be effective supportmeasures in some of the projects.

As ideal sites for hydro power projects in Himalayashas almost exhausted ,the hydropower projects are nowbeing proposed in more challenging geological conditionswhich involves tunneling through soft rocks, projectsbounded by thrust zones or tunnels passing through highcover or water bearing strata. Nevertheless, hydro powerdevelopment in India is growing at a faster pace. Some ofthe Hydroelectric Projects involving considerable tunnelinghave been commissioned in the recent past.Many

Organizations such as Satluj Jal Vidyut Nigam Ltd(SJVNL), Tehri Hydropower Development Corporation(THDC), NEEPCO, Narmada Hydro DevelopmentCorporation (NHDC),Uttranchal Jal Vidyut Nigam,NTPCetc are actively involved in development of hydro powerprojects in the country. Many projects such as NathpaJhakri (1500 MW), Tehri project (1000 MW), Indra SagarProject (1000 MW), Omkareshwar Project (520 MW) havebeen commissioned recently. With the participation ofmany private sectors the hydro power industry is gainingmomentum.NHPC ,a premier organization in the field ofhydro power development ,alone has carried out morethan 200 km of tunneling for its various projects locatedin diverse geological set up in north western, northernand north east Himalayas notable among them are UriStage-I(480 MW), Dulhasti (390 MW),Salal(690MW)inJ&K, Chamera Stage-I (540 MW),Baira Siul (198MW),Chamera Stage-II (300 MW) in Himachal Pradesh,Dhauliganga (280 MW)in Uttrakhand,Teesta Stage-V(510 MW) and Rangit (60 MW) in Sikkim,Kurichu(60 MW) In Bhutan and Loktak (105 MW) in Manipur. Asmany as 7 projects involving considerable tunneling areunder active construction stage prominent among themare Uri Stage-II (240 MW),Sewa stage-II (120MW)J&K,Parbati Stage-II (800 MW) ,Parbati Stage-III(520 MW),Chamera-III(231 MW) H.P.,Subansiri Lower(2000 MW) in Arunachal Pradesh. Total tunneling involvedin some of these projects is given in table:

Tunneling Involved in Hydropower Projects of NHPC

Sl. Project Total Tunneling*No involved (in Km)1. Commissioned Project 22.0

Uri I (J&K)2. Dul Hasti (J&K) 12.03. Salal Stage-I & II (J&K) 5.54. Chamera I (H.P) 12.55. Chamera II (H.P) 16.06. Baira Siul (H.P) 16.57. Dhauliganga (Uttarakhand) 9.08. Loktak Project (Manipur) 7.09. Rangit (Sikkim) 5.510. Teesta V (Sikkim) 23.011. Kurichu (Bhutan) 0.37

Project under construction12. Parbati Stage-II (HP) 58.013. Parbati III (H.P) 15.014. Chamera-III (HP) 20.015 Uri II (J&K) 10.016. Sewa II (J&K) 11.517 Chutak (J&K) 7.018 Subansiri Lower 11.5

(Assam/Ar.Pradesh)

2727


* Tunnels includes Intake tunnels, Desiltingchambers, Silt flushing tunnel, HRT, Feeder tunnels,various adits to HRT, Surge shaft, Pressure shaft,Powerhouse cavern, Main Access tunnel, Cable &Ventilation tunnel and TRT etc

A brief description on the salient features of theproject along with geological set up, constructionmethodology, problems and remedial measures adopted,with special reference to the tunnels and other undergroundexcavations are given in subsequent chapter :

2828


BAIRA SIUL HE PROJECT

State Himachal PradeshRiver BairaOwner NHPC LtdDesigner NHPC LtdConstruction Period Commissioned in 1981Total Length, Dia/cross 7.63 km 7.5 m, Horseshoesectional area& Shape shapedof HRTBaledh Feeder Tunnel 7.83 km, D-Shape, 2.13 m

dia

Baira Siul project is located in Chamba district ofHimachal Pradesh. The project utilizes the hydropotential of Bhaled nala, Siul and Baira river to generate750 MU power annually.

The Salient features of the project are:

A 53 m high earth and rock fill dam on Baira river. A 7.63 km long HRT

Bhaled feeder tunnel Siul weir and drop shaft A surface powerhouse having 3 units of 66 MW

each for generating 198 MW power.

The project was commissioned in 1981.

Layout of ProjectThe project has a unique layout. The flow of Baira

River is diverted through a power tunnel by constructinga rock fill dam across the river. The discharge of Bhalednala is fed to Baira just upstream of dam through7.83 km long Bhaled feeder tunnel while the flow of Siulriver is picked with diversion weir and fed into the powertunnel through two desilting chambers and a drop shaft.The surface powerhouse housing 3 Francis turbines islocated on the right bank of Siul river.

Geological Condition in HRT & Support SystemThe HRT runs mainly through the phyllitic rocks.

The 7.5 m dia tunnel has been excavated byconventional drilling and blasting method throughheading and benching. The HRT is supported by rockbolts and shotcrete as per rock class and ribs have beeninstalled in highly crushed zones; beside this contactgrouting has also been provided. The tunnel has beenlined by 20 cm thick concrete layer.

Bhaled Feeder TunnelBhaled feeder tunnel is 7.83 km long, 2.13 m dia,

2929


D-shaped tunnel for conducting water from Bhaled nalato Baira reservoir. The tunnel runs in moderately jointedphyllitic rock with schist bands.Terzagiss rockmass

classification has been adopted and the tunnel has beensupported with rock bolts, shotcrete and steel ribsdepending upon the rock class.

Layout of Baira Siul HE project

3030


BEAS SUTLEJ LINKPROJECT - ATUNNELLING PROJECT

State Himachal PradeshRiver BeasOwner BBMBConstruction Period June 1965 - June 1977Total Length of Tunnelling 26.421 km including by pass

Tunnel and chute

The year 1947 witnessed the division of the stateof Punjab and to Indias share came the waters of thethree eastern rivers, the Sutlej, the Beas and the Ravi,The Indus Water Treaty of 1960 between India andPakistan entitled India to the exclusive rights on the watersof these three rivers. The master plan was drawn to harnessthe waters to the best of advantage. The Bhakra Dam,constructed across Sutlej river, controlled the water ofSutlej for irrigation and power generation. The Beas wasthe next to be tackled, with the Ravi flowing soon after.

The Beas Project, the largest hydro-elecric-cumtunnelling Project in the country, has two units, the BeasSatluj Link Project (Unit-1) and the Beas Dam Project(Unit-II). The Beas Satluj Link (BSL) in Himachal Pradeshin the North Western lap of Himalayas diverts about4714x106 m3 (3.82 x 106 acre ft.) of Beas water from Pandohto Satluj river near village Dehar through about 40 km (25miles) long water conductor system. The remaining wateris stored at Pong primarily for irrigating the arid waterlands of Rajasthan through the Rajasthan Canal, in aplanned and regulated manner. Beas waters casacadeon a 320 m (1050 ft) fall to generate power, 660 MW infirst stage and addition of 330 MW in second stage atDehar Power Plant on right bank of Satluj before margininginto Satluj waters.

It was financed by Punjab, Haryana and Rajasthanand was managed by the Government of India (Ministryof Energy) through a construction Board withrepresentatives from Punjab, Haryana, Rajasthan andHimachal Pradesh.

The Beas Sutlej Project has a long water conductorsystems comprising Pandoh Baggi Tunnel (PBT),Sundernagar Hydel Channel (SHC), SundernagarBalancing Reservoir (SBR) and Sundernagar Sutlej Tunnel(SST), besides Pandoh Dam on river Beas at Pandohand Dehar Power Plant on river Sutlej.

Construction ChronologyThe work started in June 1965 and completed in

June 1977. The important construction schedule of tunnelsare as under:-

(i) Pandoh Diversion Tunnel June 1965 to July 1971

(ii) Pandoh Baggi Tunnel September 1965 to June1977

(iii) Sundernagar Sutlej Tunnel January 1967 to June1977

The water of Beas River was diverted into theconductor system of Beas Sutlej Link System on 7 July1977.

Pandoh Baggi TunnelGeneral

The Pandoh Baggi Tunnel with 7.62 m finisheddiameter has a design capacity of 254 .85 m3 and hasbeen constructed to carry Beas waters over a distance ofabout 13.11 km from Pandoh to Sundernagar HydelChannel. At its upstream portal, the tunnel is aligned in31.14 m upstream and parallel to the axis of Pandoh Dam.A high creased site intake has been provided to feed thetunnel from Pandoh reservoir. The tunnel has slope varyingfrom 0.272 to 0.00149.

GeologyThe tunnel was geologically classified into three

categories of reaches viz. normal, poor and very poor rockreaches. Normal rock reaches were those where the rocksare and competent, such as hard and layered phyllites.Poor / very poor rock reaches are those where the rocksare soft and sheared such as sheared phyllites, taleschists/granites. Distress reaches fall in the category ofvery poor rock reaches.

Identification and Valuation of Geo TechnicalProblems

On actual tunnelling, the phyllites, comprisingabout 30 percent of total length, had offered good tosatisfactory tunneling conditions, which was thus onegrade better than the satisfactory to fair type as wasanticipated. The granite reach offered good, satisfactoryand poor tunneling conditions in 56, 32 and 12 percentlengths, respectively, as against 50, 30 & 20 percent (aswas forecasted), thus indicating slightly better conditionsthan anticipated. However, in two reaches of sheared andkaolinised granite encountered, in what were inferred tobe tectonically active faults zones, aggregating about 762m (2000 ft) in length and approximately to 6 percent ofthe total length of the tunnel, sever squeezing pressureshad been encountered. This condition was not visualizedin the earlier geological forecast. Tunnelling through thesetwo very poor reaches took 31 months as compared to13 months taken for tunneling through a good rock reachof equivalent length.

Tunnelling Cycle and Selection of EquipmentExacavation of PBT was carried out mainly from

three headings. The tunnelling cycle broadly consisted of

(i) Drilling, blasting and ventilation.

(ii) Mucking and haulage of rock.

3131


(iii) Ribbing and concreting the gap between rock andsteel supports.

Probing the StrataThe strata ahead of the tunnel heading was probed

before doing the heading blast, where the geology of thestrata was not exactly known. A 10 m deep probe holehad to be drilled with CP machine.

Concrete LiningThe concrete lining has been done in the tunnel

(i) To give adequate protection to the steel rib supports

(ii) To prevent leakage from the tunnel

(iii) To reduce hydraulic losses and

(iv) To withstand such anticipated minor rock loadslikely to be developed subsequently

(v) To accommodate reinforcement.

The thickness of concrete lining inside the rib waskept to 254 mm (10 inch). The thickness was increasedto 381 mm (15 inch) in very poor rock reaches. Concreteof 211 kg/cm2 strength at 28 days was specified to beused in lining. Overt Concreting and invert concreting wasused.

GroutingContact grouting, consolidation grouting and cavity

grouting was done.

Inside View of Pandoh Baggi Tunnel

Sundernagar Satluj TunnelGeneral

Sunder Satluj Tunnel of 8.53 m (28 ft) dia and 12.35km (7,67 miles) long is a power tunnel which takes offrom Sundernagar Balancing Reservoir and terminates intoDehar Surge Shaft from where three penstock headersfan out. A conventional type semi - circular intake structurehas been provided to feed the tunnel. The tunnel has beendesigned to carry 403.52 m3 (14250 ft3) / s of water forrunning 6 generating units of Dehar Power Plant. At inlet,

tunnel comprises a twin rectangular section transitionedinto 8.53 m (28 ft) dia circular section in a length of 22.56m (74 ft.). To expedite the work of tunnelling twoconstruction Adits, viz Harabagh Adit and Bharari Aditwere provided. After construction of tunnel, junction ofBharari Adit was closed with a concrete plug and hollowconcrete plug at Harabagh Adit junction was provided witha gated opening to provide access for inspection and repairof tunnel. If so required during closure of tunnel. Toventilation shafts opening in the Nihari and Bumka Nallahbeds were provided during the construction which weresubsequently closed by the concrete plugs. The tunnelhas been concrete line in its entire length reinforced in areaches where the rock is poor or where the rock cover isinadequate. The total quantity of concrete used in thelining is 0.53 x 106 m3 (0.69x106 yd3). The construction oftunnel involved excavation of 1.21 x 106 m3 (1.58 x 106 yd3)of rock.

For construction facility, execution of SundernagarSatluj Tunnel was taken up from High heading (i) PungIntake portal Adit junction to downstream (ii) Bharari AditJunction to upstream and (iii) Bharari Adit junction todownstream.

GeologyThe alignment of Sundernagar Sutlej Tunnel runs

through an area of complex geology. The variousformations encountered in the area are shails comprisinglimestone, dolomites, khaira quartzites, red shafts andinfra shails comprising traps, phyllites and schists withquartzites. These rock formations, which are also chargedwith water, were considered extremely poor tunnelingmedia, except for lime stones and dolomites.

The tunnel has been geologically classified intothree categories of reaches viz. normal, poor and verypoor rock reaches. Normal rock reaches are those wherethe rocks are hard and competent such as layered arecrumbly dolomite and limestone. Poor/ very poor rockreaches are those where the rocks are soft and shearedsuch as sheared to crushed dolomites and limestones.

AlignmentThe alignment of this tunnel was tunnelised after

extensive exploration by drilling and drifting. The task inchoice of the final alignment was, (i) to avoid Suketi lakesediments and Jaunsar phyllites traps, etc. (ii) to keepthe tunnel at safer distance from the krol thrust, (iii) toavoid crossing of maximum possible faults and availabilityof construction adits of reasonable length. Thus forachieving these objectives, atleast 4 kinks in the alignmentwere unavoidable. The final alignment, althoughsandwiched between the major fault features i.e., the krolthrust in the west and the bobri Khad fall in East avoidscrossing of all the strike faults and runs in best availablerock units i.e. limestones and dolomites of the Shafts.

Tunnelling Cycle and Selection of Equipment.For speedy excavation of tunnels, Adits are

required to open at as many places as possible. In this

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tunnel, two above referred Adits had been provided and inall, five headings were available for working. The tunnellingcycle broadly consisted of :

(a) Drilling, blasting and ventilation for exhaust of flamescushions.

(b) Mucking and haulage of rock.

(c) Ribbing (Fixing of steel supports) and concretingthe gap between rock and steel supports, calledInitial concreting.

Tunnel ExcavationSince the designed bed level of tunnel at Intake

was much below the existing natural surface level, so asa preliminary work, a pit of size 152.4 into 152.4 (500x500ft) and 27.43 m (90 ft) deep was excavated to facilitatethe work of tunnelling excavation. To reach the work sitea suitable ramp at a slope of 1 in 12 was provided. Afterthe excavation of the pit and meeting ramp are, the initialconstruction at the main heading was taken up where notunnel excavation was required. For this, portal type ribsof ISMB 150 x150 mm (6 x 6 in) size were erected on4.27 (14 ft). The valve plates of 410 mm (16 in) width wasplaced on either side under ribs on sides and the top, 900mm (3 ft) thick concrete was placed. This initialconstruction work at the main heading was completed inJune 1969 in a months time.

The strata encountered was some what similar tothat of river bed, hence only 1.2 m (5 ft) length of tunnelwas excavated and ribs installed. To proceed further,blasting holes were drilled at 900 mm (3ft) all aroundleaving in clear gap of 600 mm (2ft) from the ribs. Gelatine60% and half second delay detonator were used forblasting.

Drilling EquipmentsTwo types of drilling machines i.e., CP drilling

machines and Atlas Copco machines were used.

Concrete LiningThe concrete lining has been done in the tunnel

(i) To give adequate protection to the steel rib supportsto prevent leakage from the tunnel

(ii) To reduce hydraulic losses and

(iii) To withstand such anticipated minor rock loadslikely to be developed subsequently.

The thickness of concrete lining inside the rib waskept to 254 mm (10 inch). The thickness was increasedto 381 mm (15 inch) in very poor rock reaches. Concreteof 211 kg/cm2 strength at 28 days was specified to beused in lining. Overt concreting and invert concreting wasused.

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CHAMERA HE PROJECTSTAGE- I

State Himachal PradeshRiver RaviOwner NHPC LtdDesigner NHPC LtdContractor/s SNC/Acres, CanadaConstruction Period Commissioned in 1994Total Length, Dia/cross 6.4 km, 9.5 m,sectional area & Shape of Horseshoe shapedHRTUnderground Powerhouse 112 m x 21.5 m x 37 mOther Tunnels (Diversion 3.75 kmtunnel, Constructionadits, Surge Shaft,Pressure shaft, MAT, Cable &Vent. tunnel, TRT

Chamera H.E.Project located on river Ravi inChamba Distt of Himachal Pradesh lies in lesserHimalayas. The 540 MW project executed by NHPC incollaboration with SNC/Acres, Canada wascommissioned in April 1994.

The salient features of the project are:

A 140 m high (from deepest foundation level) highconcrete arch gravity dam.

10.7 m dia, horse shoe shaped Diversion tunnel A 9.5 m dia, 6.4 km long , horse shoe shaped

head race tunnel

25 m dia, 84 m high surge shaft 8.5 m dia 157 m high pressure shaft Underground powerhouse of dimensions 112 m

(L) x 24 m (W) x 37m (H) with three units of 180MW each.

Transformer hall of dimensions 114 m (L) x17 m(W) x 14 m (H)

A 9.5m dia ,horse shoe shaped, 2.4km long, tailrace tunnel

Head Race TunnelLayout

The head race tunnel is constructed on the rightbank of river Ravi.

The 9.5 m dia 6.4 km long HRT passes through afolded sequence of phyllite, carbonaceous phyllite,graphitic schist and phyllitic limestone of DhundiaraFormation. The rocks of Dhundiara formation areunderlain by Shail Thrust which rest on meta volcanics ofPir Panjal Formation in which the last lap of the powertunnel was excavated. The maximum cover over thetunnel is about 800m.

The power tunnel has been excavated in twostages viz heading and benching. The 6.4 km long tunnelwas initially planned to be excavated through threeconstruction adits-Adit-1,Adit-II and surge shaftadit .However, due to slow progress of works andproblematic carbonaceous phyllite zone at Face-3 ,anotheradit (Adit-III) was provided on the right bank of Lohadedanala.

Problems Encountered and Remedial MeasuresAdopted

Tunneling through weak rock mass particularlycarbonaceous phyllites associated with heavy waterseepage, formation of cavities due to roof collapse,crossing of Shail Thrust and interception of river bornematerial while passing under Baggi nala crossing werethe major problems which were encountered during

tunnel construction. Remining andrehabilitation of some portion of thetunnel,multi drift method in weakzones, providing steel ribs andcontinuous monitoring ofdeformations by systematicinstrumentation during constructionwere some of the techniques used .The problems faced during tunnelexcavation along with remedialmeasures have been brieflydiscussed:

Face-3 of the Power tunnel,excavated downstream from Adit-1pierced through a 400 m wide bandof carbonaceous phyllite/graphiticschist between RD 1150 m to

Chamera Dam Stage-I

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1550 m.The ribs provided as support got deformed over aperiod of time .As the deformed ribs could not beaccommodated in the designed section, the entire reachin carbonaceous phyllite was re-mined and rehabilitated.

Downstream of Adit-III the superincumbent coverover the tunnel rises continuously and attains a maximumheight of 800 m.Here,phyllites with bands ofcarbonaceous phyllites were intercepted at the tunnelgrade leading to squeezing ground conditions. Some ofthe worst cavities were formed in this zone.

In Face-4 at RD 4925 a deep cavity of about 8 mwas formed on the left wall due to crushed rock mass ofphyllite associated with profuse seepage of the order of200-300 l/min. This section was treated by forming abulkhead at the face, backfilling the cavity by concreteand grouting the surrounding rock mass. Headingexcavation from RD 4931 m was also carried out by multidrifting.

While crossing the 800 m thick Shali thrust zonepoor to fair quality phyllite rocks were encountered. Thetunnel witnessed frequent collapses in this zone. It wasstabilized by extensive grouting and backfilling the cavityby concrete.

When tunnel face was advancing below Baggi nala,in a low cover zone, riverine overburden was interceptedbetween RD 6329-6363 m. Entire length in RBM wasexcavated by multi drift grouted and supported by steelribs.

Instrumentation

In view of weak carbonaceous rock which has atendency to deform even after supported by steel ribs, acomprehensive programme of instrumentation waslaunched simultaneous with the excavation. Tapeextensometers were installed to measure the deformationrates. The data obtained were analyzed for augmentingthe support.

Underground Power House

The underground power house cavern is 24.5mwide, 112.5 m long and 31.6 m high. The power housecomplex is located in fine grained meta basic rock. Therock mass is blocky to foliated and is intersected by fivesets of joints. Foliation joints are continuous, slightlyundulating and moderate to closely spaced. Interfolialshear seams ranging in thickness from 1mm to 10 cm,filled with clay and rock fragments traverse the rock massat 2 m to 4 m interval. The orientation of power house hasbeen kept normal to the prominent foliation joints tominimize the adverse effects of these discontinuities overthe excavation of cavern of such large span.

Insitu rock mechanic tests viz. flat jack and plateload tests and laboratory tests were conducted todetermine the engineering properties of rock mass.Instrumentation by multiple point bore hole extensometers,tape convergence meter and load cells were done todetermine the deformation during various stages of cavernexcavation.

The crown of the powerhouse was supported by6m long; 25 m dia rock bolts at a spacing of 1.5 m c/calong with 10.5 m long anchors at a spacing of 4.5 m c/cas secondary support. The walls were supported by 7.5mlong rock bolts.

Cracking in shotcrete due to stress related problemswere noticed in powerhouse cavern particularly in thedownstream wall. A big cavity was also formed in thetransformer cavern/ draft tube, concurrent with theexcavation of the power house. This cavity was stabilizedby grouting however the falling of rockmass could not bestopped during benching operation of power house cavern.The power house cavern excavation remained suspendedfor some time and the cavity was treated by grouting andthe support in power house cavern was also strengthenedby installing 12 m long bolts. Continuous monitoring ofpower house excavation was also done by instrumentation.

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Tail Race TunnelThe 2.4 km long Tail race tunnel passes through

meta volcanics and a sedimentary sequence of shalesand sandstone of Muree Formation separated by Murreethrust. One of the unique features of the tunnel is its

crossing under Ravi River at a depth of about 40 m belowthe river bed. Incidentally, no serious problem was metthroughout the length of TRT.However, crossing of 270 mthick Ravi shear zone/Murree thrust, tunneling below riverbed and tunnelling under multi level Simbleu terrace weresome of the unique features of tail race excavation.

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CHAMERA HE PROJECTSTAGE II

State Himachal PradeshRiver RaviOwner NHPC LtdDesigner NHPC LtdContractor/s Jaiprakash Industries/

Indo-Canadian HydroConsortium

Construction Period Commissioned in 2003Total Length, Dia/cross 7.83 km, 7.5 m Horseshoesectional area & Shape shapedof HRTUnderground Powerhouse 100 m x 22 m x 39.7 mCavernOther Tunnels (Diversion 8.0 kmtunnel, Constructionadits, Surge Shaft,Pressure shaft, MAT, Cable& Vent.tunnel,TRT)

Chamera Hydroelectric Project, Stage-II (300 MW)is a run of river scheme on river Ravi in the upstream ofChamera-I Hydroelectric Project in Chamba Distt. ofHimachal Pradesh. The project has a capacity to generate1500 MU of energy in 90% dependable year utilizing agross head of 267m. The CCEA clearance for the projectwas accorded in May 1999. The project was executed onturn key basis by Indo-Canadian Hydro Consortium (ICHC)and got commissioned in 2003 in a record time of 4.5years.

The salient features of the project are:

A 40 m high concrete gravity dam across river Ravi A 303 m long diversion tunnel having segmental

circular section with overt radius of 5.07m and invertradius of 10.485 m

7.0 m dia ,7.83 km long horse shoe shaped headrace tunnel

17.2 m dia,104.5 m high surge shaft 3.0 m dia,3 nos pressure shaft,209.5 m high Underground powerhouse 100 m x 22 m x 39.7 m

having 3 units of 100 MW capacity each.

Transformer hall 88 m x14 m x 13 m A 3.4 m long, 7.0 m dia tail race tunnel.The Head Race Tunnel

Geological ConditionThe Project area lies in lesser Himalayas. In the

project area mainly phyllitic rock with phyllitic quartziteare exposed. The 7 m dia, 7.83 km long HRT is plannedon the right bank of river Ravi. The HRT constructionwas facilitated through three adits having a cumulativelength of 560 m..The hill in which power tunnel is locatedis deeply incised by Kalsuin and Jarangla nala besidesmany perennial streams, as such, heavy seepages wereanticipated in certain zones, however, the constructiondid not relate these nallahs to any zone of principalgeological weakness. The maximum cover of 940 m wasobserved for 13% of the tunnel length. Mainly fair rockclass (RMR 40-60) was encountered in 93% of the tunneland poor rock in 7% of the tunnel.

Excavation and Support SystemThe excavation was carried out through

conventional drilling and blasting method. The excavationwas supported by shotcrete (with or without steel fibers),wire mesh and rock bolts and depending upon the rock

3737


class by steel ribs and backfilled concrete. The tunnelwas concrete lined using 30 cm thick concrete.Contiuoustraveling type shutters of CIFA make were utilized forcontinuous lining. This enabled the concreting of entire

tunnel section in one go instead of conventional mode ofconcrete lining of overt and invert as separate activity.The entire concrete of HRT was achieved in 16 monthsas against the 23 months, planned for this activity,

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A View Of Gantry

Problems Encountered and Remedial MeasuresAdopted

Problem of cavity formation due to sheared rockwith heavy seepage encountered between RD 1301 and1305 m was rectified by fore poling, installation of steelsupport and backfilling with concrete, installation ofconcrete lagging and welded beams between the ribsand grouting through a drift excavated parallel to thetunnel.

In the reach between Ch 3087 m to 3110 mmeasured from u/s end of HRT, overburden materialcomprising of boulders, gravels and clay associated withcopious water inflow was intercepted. Steel ribs providedin this section got deformed. The deformation wasmonitored by installing tape extensometers. Themaximum cummulative deformation ranged from 650-700 mm above crown and 300 mm below springing level.In order to enhance the stability, consolidation groutingof the rockmass was carried out.

Underground PowerhouseThe powerhouse cavern is 100 m long, 22 m wide

and 39.7 m high. The crown level is at El 926m.Thepowerhouse is placed 90 m deep inside the hill with amaximum cover of 275 m over the cavern. The orientationof the longer axis of powerhouse cavern is aligned in N30E-S 30 W direction and is almost perpendicular to majordiscontinuity planes.

The rock types in the powerhouse area aremetasedimentaries comprising of quartzites, interbeddedwith phyllitic quartzite and quartzitic phyllites, belongingto Chamba Formation and intruded by Dhauladhargranites.

Rock mechanic tests for stress measurement byhydro fracturing method were conducted inside the cabletunnel by NIRM, Karnataka. The maximum horizontalprincipal stress was found to be in the range of 8.46 to9.90 MPa and the direction of principal stresses wasN400E.

As such, no major problem was faced duringexcavation of power house cavern.

3939


Tail Race Tunnel under construction

4040


CHAMERA STAGE III HEPROJECT

State Himachal PradeshRiver RaviOwner NHPC LtdDesigner NHPC LtdConstruction Period Under constructionTotal Length, Dia/cross 15.99 km 6.5 m Horseshoesectional area& Shape shapedof HRTUnderground Powerhouse 100 m x 18.6 m x 42 mOther Tunnels (Diversion 3.5 kmtunnel, spillway tunnel,adits, surge shaft, pressureshaft,C&VT,TRT)

Chamera Hydroelectric Project, Stage-III (231 MW)is a run of river scheme on river Ravi in the upstream of

300 MW Chamera-II Hydroelectric Project in ChambaDistt. of Himachal Pradesh. The estimated annual energygeneration from the Project in a 90% dependable year is1108.17 MUs and will provide a minimum of 3 hrs/daypeaking power in the power system of the northern regionduring lean period. The project will utilize a gross head of230 m and net rated head of 200 m. The project is inadvance stage of construction.

The Project comprises of:

Diversion Tunnel 460 m long, horseshoe shaped,8.2 m dia.

Concrete gravity dam of 68 m height, 78 m lengthat top.

HRT of 6.5 m dia. horseshoe shaped & 15.99 kmlength.

24 m dia and 110 m high restricted orifice typeSurge shaft

5.2 m dia and 450 m long Pressure Shaft trifurcatinginto branches to feed three Francis vertical axisgenerating units.

Underground Power House to house three units of77 MW each

TRT 6.5 m dia, 125 m long, horseshoe shaped.

Geological Section of HRT

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Rock Support Work in Progress in HRT

Head Race TunnelLayout

The 15.9 km long, 6.5 m dia HRT is beingconstructed through six nos of construction adits varyingin length from 65 m to 366m .

Geological ConditionThe project falls within the lesser Himalayan zone

and comprises of unfossiliferrous meta sediments of

middle to early Paleozoic age belonging to ChambaFormation which are overlain by Manjir Formation whichin turn is overlain by fossiliferrous Salooni Formation ofPermo-carboniferrous age. The country rock is intrudedby younger Dhauladhar granites.

The tunneling is being carried out mainly in phylliticquartzite rocks which are strong, foliated rock. Out of15.9 km about 14 km has been completed. Mostly goodto fair rock has been encountered in the excavatedportion.

Excavation and Support System

The excavation is being done by drill& Blast methodtaking full face blast. Most of the tunnel is supported byrock bolts and shotcrete.

Problems Faced During Construction and theirSolutions

So far HRT excavation is free from any majorproblem except between RD 430-482 m where cavitieshave been formed due to presence of weak andpuckered phyllite bands. Class IV/V support comprisingof rockbolts, shotcrete and steel ribs has been providedin this reach.

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CHUTAK HE PROJECT

State Jammu & KashmirRiver SuruOwner NHPC LtdDesigner NHPC LtdContractor/s M/s HCC LtdConstruction Period Under constructionTotal Length Dia/cross 4.78 km 5.9 m , Horseshoesectional area & Shape shapedof HRTUnderground Powerhouse 83 m x 15.5 m x 34.5 mOther Tunnels (Adits, 0.88 mPressure shaft, surge shaft,TRT)

Chutak H.E. Project is located in Kargil district ofLadakh region of Jammu & Kashmir. It is planned as arun-of-the-river scheme to harness the hydro potentialof the Suru river (a tributary of Indus). The estimatedannual generation from the project in a 90% dependableyear is 212.93 MUs. The project is being taken on therequest of J&K government and the entire powergenerated from the project would be absorbed in theLadakh region. CCEA approval has been accorded to

the project on 24.08.2006.The project is under constructionby NHPC.

The project envisages co

Documents

History of Tunnels.pdf