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TUNNEL BORING MACHINES FOR THE SRISAILAM CANAL TUNNELS,

ANDHRA PRADESH, INDIA

David Salisbury1, Desiree Willis

2

1Robbins Asia Pacific, China Hong Kong City, Canton Road, Kowloon, Hong Kong SAR, China

2The Robbins Company, S.194th St., Kent, Washington, 98032, United States of America

Keywords: TBM, India, hard rock, OFTA

INTRODUCTION

The city of Hyderabad and the surrounding province of Andhra Pradesh, India has, for decades,

faced an increasing struggle for a reliable source of fresh water. Local drinking water is known to

carry excessive levels of fluoride, which poses a long-term health risk to the local population, their

livestock and the diverse natural flora and fauna of the region.

To address this problem the government of Andhra Pradesh has commissioned the Alimineti

Madhava Reddy (AMR) project comprising over 100km of aqueduct canals and tunnels to transfer

water from the Srisailam Reservoir to 120,000 hectares of farmland, as well as providing a greatly

improved source of drinking water to over 500 villages and the city of Hyderabad.

As part of this network, one of the longest tunnels ever constructed in India is being driven across

the Amrabad plateau, which contains the Rajiv Gandhi wild life sanctuary and the Nagarjuna Sagar

reserve, at 3568km

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Indias largest tiger reserve. To minimize the environmental impact on thereserve, the contractor Jaiprakash JV elected to use two tunnel boring machines (TBM), one

working from each portal and meeting in the middle. At 43.5km in length, and 9.2m diameter,

tunnel-1 will be the longest tunnel in the world to be constructed without any intermediate points of

access.

Another section of the overall scheme, the Pula Subbiah Veligonda project will construct a similar

9.2m diameter, 19.2km long tunnel from the right bank of the river, beneath the Nagarjuna Sagar

reserve, to irrigate 160,000 hectares of farmland to the south.

This paper will describe the planning of the project, and the selection and procurement of the

TBMs. It will also outline the development of the on-site first time assembly (OFTA) method now

being adopted successfully on this project and a number of Robbins projects around the world.

Finally it will provide an update on the progress and difficulties overcome on the AMR project upto the time of writing.

PROJECT BACKGROUND

The Andhra Pradesh region of India has an average annual rainfall of just 925mm, making it one of

the most arid states in India. A scheme to provide a clean reliable and cheap water supply to this

region has been planned since 1983. These projects are two of a number of large irrigation schemes

intended to greatly improve the availability and reliability of water around the region.

The two projects emanate from the Srisailam reservoir and will provide water to four districts in

Andhra Pradesh. The AMR and Veligonda tunnels will utilize three identical 10.0m diameter

Robbins Double Shield TBMs and conveyor systems, and will also be supplied with Robbins

cutters, spare parts, and field service personnel.

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Alimineti Madhava Reddy (AMR) Project

The AMR Project begins at the left bank of the Srisailam Reservoir on the Krishna River. Two

main tunnels will distribute surplus water through a network of canals to the plains of the Nalgonda

District. The water will be used to irrigate 120,000 hectares of farmland and will provide potable

water to 516 villages.The main tunnel, Tunnel-1, starts from an

intake basin just upstream from the

Srisailam dam and travels from south to

north for 43.5km to a balancing reservoir

on the Dindi River, making it the worlds

longest TBM-driven tunnel without

intermediate access.

A second, 7.3km long, 8.7m diameter,

drill and blast tunnel running northeast

from the Dindi river will then distribute

the water to a network of canals.

Pula Subbaiah Veligonda Project

On the opposite side of the Srisailam

Reservoir is the Pula Subbaiah Veligonda

project.

Two parallel, 19.2km long tunnels,

Veligonda Tunnel-2, will transfer 1.2

billion m3

of floodwater annually via a

network of five canals to over 1,600km2

of farmland in the three districts ofPrakasam, Nellore, and Kadapa.

GEOLOGY

The geology of the Andhra Pradesh region is generally very stable, unlike the conditions in North of

the country. It is part of the ancient South Indian Peninsular Shield, and consists of two main rock

types; quartzite and granite. The project site is in a remote area with very little previous geological

information available. Therefore the geology of the tunnel has been interpreted mainly from surface

mapping and aerial photography. The main contractor, Jaiprakash, completed a walkover of the

surface and survey of all river valleys above the tunnel. This led to some concerns over the lack of

cover to the tunnel in one river valley, resulting in a realignment of the project.Other useful geological information on the southern section has been interpolated from the nearby

underground power stations and other related excavations on the Srisailam reservoir, some 5km

from the tunnel inlet portal.

At the AMR Project the ground conditions from the southern inlet consist of quartzite zones with an

unconfined compressive strength (UCS) of typically 80 to 250MPa, and up to 450MPa. These are

layered and separated by shale for approximately 60% of the length. The remaining 40% of the

northern section of the tunnel will pass through granite with a UCS of typically 100 to 230MPa.

Figure 1 AMR and Veligonda Projects location

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PROJECT CONSTRAINTS

Alignment

The vertical alignment is a single downhill 0.03% gradient from south to north. The concern over

the low cover geology led to a revised horizontal alignment from the initial straight tunnel. The

revised alignment incorporates two 10km radius curves at the southern end to push the alignmentapproximately 1km West as it crosses the Mamidirevu Vagu valley, thus achieving over 100m of

rock cover. The large radius curves allow the segments to be designed as if the tunnel were straight

with only plane correction packing required.

Programme

The entire project is expected to take about 60 months to complete, and should be operational by

December 2012. This relatively tight schedule for such a long drive effectively dictated the use of

two double shield TBMs, with other considerations to mitigate the programme including the OFTA

method allowing the Downstream outlet portal TBM to be launched in May 2008. However, at the

inlet portal the works area would not be ready until the end of April 2009, with the TBM scheduled

to start assembly in May 2009 and launched in August 2009.

Personnel

Jaiprakash has extensive experience in civil construction and drill and blast tunnelling, but little in

the field of TBM tunnelling. It was therefore essential to them that the TBM supply contract

included personnel suitably experienced in hard rock TBM tunnelling to work with the Jaiprakash

workforce. To meet this requirement, Robbins has a full time site staff including both Indian

nationals and expatriates. These personnel carry out all the maintenance of the TBM as well as

providing supervision of cutter changing and the overall tunnelling operations. Training the local

workforce in the various specialized skills required for efficient operation of a high performance

TBM has led to a longer than expected learning curve at the start of the outlet tunnel drive.

Portals

The outlet portal surface area was maximized to be 45m wide and 160m long to allow the full

length of the TBM to be assembled to minimize the time taken for launching the machine. A deep

trench was excavated in the granite to provide the site formation, see Figure 2.

However, at the inlet portal the tunnel invert level is 30m below the top water level of the reservoir,

protected by a bund wall. This meant that the site had to be reduced to 120m by 45m and would

take much longer to prepare.

TBM SPECIFICATION

Selection processFollowing a detailed selection process double shields

were eventually finalized as the best choice for the

tunnel excavation by Jaiprakash. Consideration was

given to using open TBMs and single shielded TBMs.

However, the simplest and most reliable solution, of

using two 10.0m diameter double shield machines

boring from opposite ends of the 43.5km tunnel, at the

inlet and outlet portals was the final choice.

Figure 2 AMR outfall portal site

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The main reasons behind these decisions were:

Construction of lining simultaneously with excavation Envisaged difficulties with the geology and unknown associated risk No temporary support required, and difficulty to quantify Optimized programme as no need for follow on concrete lining Two high performance TBMs of the same type, one working from each end.

Cutters

The machines utilize back-loading 20-inch diameter cutters, which provide for a more efficient

excavation and longer cutter life. Specially designed drive motors also allow each machine to run

at a higher than normal rpm, compensating for low expected penetration rates in the hard rock. In

squeezing ground, each cutterhead is also capable of vertical movement to allow for overboring.

Segmental lining

Each machine will install 300mm thick concrete segments, which will serve as a final liner to make

the finished tunnel diameter of 9.2m. As the TBMs bore, invert segments are laid directly on the

excavated surface and the 6+1 ring erected using dowels on the circle joints and spear bolts on the

radial joints. Stability of the segment rings is achieved through a combination of pea gravel

injection and grouting to fill the annulus outside the lining. Boring through precast blind weep

holes in the concrete lining to relieve external pressure can also be used to mitigate groundwater

seepage.

Probe drill

A probe drill on each of the machines can be utilized to verify geology 30m ahead of the TBM.

The drill is capable of 360 rotation and can alternatively serve for drilling grouting arrays. Large

40kW dewatering pumps located on the back-up have been specially designed to pump any wateraway from the tunnel face. This is required on both the uphill and downhill drives, as the final

hydraulic gradient is so shallow.

Data logging

To monitor TBM performance throughout the project, a newly designed data logging system has

been installed on each machine. Real-time meters allow the measurement of parameters including

cutterhead motor amperage, cutterhead power, and gripper cylinder pressure. Information is relayed

to bespoke designed software which allows multiple choice displays, viewable by the machine

operator, Tunnel Superintendent and Engineers to allow monitoring and adjustment of all TBM

equipment. Data can also be generated in graphic form to view trends over time. The data logging

system on these machines is more advanced than those previously used, monitoring a greaternumber of parameters, allowing equipment performance to be examined and maintenance planning

to be performed on a continuous basis.

TBM Backup

The backup consists of seven decks and a towed California crossing. The backup has been designed

to run on an outer rail which is recycled once this is exposed at the rear of the equipment. All the

backup structure was fabricated in India.

Each supply train can deliver enough materials and segments for two complete excavation cycles all

unloaded in one fast operation. At the full 22km length of the drive it will take over 1.25 hours of

travelling time for the supply trains to reach the TBM.

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The backup decks have two main levels and carry all the necessary equipment for running the

TBM:

Deck 0 TBM conveyor, transfer conveyor and bridge gantry, towing connection betweenTBM and backup, hydraulic power packs; Rail laying area.

Deck 1 and Deck 2 Electrical cabinets, transformers and VFD equipment; Segmenthandling equipment on the lower deck

Deck 3 Invert and secondary grouting mixers, pumps and material handling equipment Deck 4 Pea gravel injection equipment, storage hoppers and handling system Deck 5 Water supply and dewatering system. Emergency refuge chambers Deck 6 Air compressors, high voltage cable reel and ventilation equipment Deck 7 Ventilation equipment and dust scrubber system, duct magazine and hose reels California crossing Towed by the backup and running on the backup outer rails.

The backup decks are over 120m long and weigh unloaded 450t.

Emergency Chambers

Safety concerns in long tunnels necessitate the use of refuge chambers. On the AMR TBMs

chambers have been included which are able to accommodate the full working shift. Two separate

pressurized containers on the back-up decks provide a capacity for 32 people. The containers are

connected to a compressed air line from the surface. Should a fire or similar emergency occur,

compressed air is stored in cylinders sufficient for 32 persons for a two hour period should

pressurization not be possible.

Veligonda Project

A third identical 10.0m diameter Robbins double shield machine was designed for the nearby

Veligonda tunnel-2. Design elements of this third machine, such as the use of back-loading 20-inchcutters, are the same as those for the two AMR machines. The machine was delivered to site in late

2008, again with OFTA being used for its commissioning procedure. The machine is programmed

to commence excavation in March 2009 alongside another 7.7m diameter TBM excavating a

parallel tunnel.

CONTINUOUS CONVEYORS

A continuous conveyor system was

selected as the most efficient method of

spoil handling for the projects. The

system is the longest conveyor drive

Robbins conveyor division has everprovided, with the AMR tunnels each

containing two reaches of 11.25km and

the Veligonda tunnel extending a single

flight of 19.2km. To take the belt to

greater lengths, more powerful drives are

needed with booster drives at

approximately 5.5km spacing. The

914mm wide steel cable belt system will

be powered by a total of seven drive

motorsone main drive with two 300kW

motors at the tunnel portal plus threebooster drives with a total of five motors

Figure 3 Stacker conveyor at outfall portal

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inside the tunnel. They have a capacity of 800 tonnes per hour, with a speed of 3m/s and a cassette

capacity of 600m.

Once the TBMs bore the first 11.25km of their respective drives, the fixed tailpiece and the belt

storage cassette will be moved inside the tunnel, allowing for the continuous addition of belt to the

next conveyor flight. Muck removed during the course of the project will be recycled as backfillgravel, segment aggregate and rock fill on many of the projects balancing reservoirs.

At the outlet portal is an incline conveyor and a stacker conveyor. The stacker allows a stockpile of

9m height over an arc of 45 degrees. 5000m3

can be stockpiled with muck removal by truck.

The construction sites for the AMR and Veligonda tunnels are two to three hours away from each

other by road, making it possible to exchange conveyor components; hence the conveyor systems

themselves are nearly identical for maximum efficiency.

ON-SITE FIRST TIME ASSEMBLY

Robbins first developed OFTA for the 14.44m diameter Niagara TBM as a way to build a large

diameter machine in a relatively small amount of time. OFTA allows TBMs to be initiallyassembled onsite, rather than in a manufacturing facility. The process eliminates all pre-assembly

and disassembly in workshops and requires fewer total man-hours as a result. The reductions in

man-power and shipping of large components generally add up to significant cost savings. By

analyzing the risks and benefits in advance it is possible to determine on which projects this method

will provide time and cost savings.

Pre-planning is generally done months in advance to ensure that adequate personnel, cranes, and

other lifting devices are available at the site. Multiple quality control measures are put in place to

make sure the OFTA process runs as efficiently as possible. A typical project requires that Robbins

engineers develop a complete set of procedures for the assembly. Key personnel are then provided

to oversee the assembly, including mechanics, electrical engineers, welders, fitters, and field servicesupervisors.

Several developments in the TBM manufacturing process have assisted the development of OFTA:

The ability to visualize accurately the assembly of component parts using 3D graphics CAD

software has greatly reduced the risk of clashes and conflicts between components which was not

previously available with 2D drawings; The use of modular components allows each component to

be tested at its own point of manufacture, eliminating any real need for repeat factory testing at a

TBM assembly shop. Standardisation of TBMs and repeat designs allows many of the testing and

commissioning problems to be eliminated through the generations of machines.

Since its inception at Niagara, OFTA has

been used in the planning for a number

of machines and was immediatelyrecognized as offering potential benefits

to the AMR and Veligonda projects.

OFTA at the AMR outlet portal

The TBM order for the AMR project was

signed in May 2007 and components for

the first 10m machine began arriving in

late 2007 only eight months after the

finalizing the order, with all components

for the first TBM delivered to site within

13 months.Gantry cranes capable of lifting up to

170 tonnes were assembled at the outfallFigure 4 Assembly of the TBM at the outfall portal

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portal to hoist machine components into the launch pit. Machine components including the

cutterhead, gripper system, forward shield, and telescopic shield, were assembled in a concrete

cradle, see Figure 4. The finished TBM then crawled forward by reacting against invert segments

installed progressively up to the tunnel entrance, see Figure 5. The back-up decks and other

supporting equipment was assembled concurrently as well as the main components of the conveyorsystem.

The whole assembly process was

completed in 16 weeks, this was slightly

longer than planned and some minor

miss-matches of components had to be

overcome. The remoteness of the

project and the lack of an experience

local labour force to support the

Robbins site team added to the delays.

Nevertheless, the whole process of

TBM order to commissioning using theOFTA process led to a saving of over 4

months on the critical path of the

project.

EARLY CHALLENGES

Groundwater inflow

The granite section of the tunnel is blocky and fractured with dolerite dykes, this has led tosignificant water flowing into the face. This water is picked up by the cutterhead buckets and

deposited on the conveyor, this forms an abrasive paste which causes rapid wear to the conveyor

scrapers. Water draining from the belt also affects the segment erector causing mechanical

problems. Different scrapers were tried to improve this problem. Water carried along the conveyor

system also caused a problem for the inclined conveyor and the stacker conveyor at the portal. The

stacker conveyor angle has been reduced to limit this problem.

Boulder damage to the conveyor

The blocky rock led to large boulders

entering the cutterhead, and being dropped

onto the conveyor.Some of these boulders block in the transfer

hoppers causing massive tears in the

conveyor belt. Boulders also would roll

back and drop off the incline and stacker

conveyor, see figure 6. Additional grizzly

bars were added to the cutterhead openings

to reduce the size of rocks passing into the

cutterhead. This has also helped with the

problems of boulders.

Other issuesThe project suffers regular power outage causing loss of production and safety concerns. The site

has full generator back-up but this takes time to start and is expensive to run.

Figure 5 The fully assembled TBM

Figure 6 Boulders on the stacker conveyor

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The TBM tail shield is open-bottomed which allows the invert segment to be set directly against the

exposed rock surface. Early problems with the ring build required the opening size to be widened to

cover the bottom three segments. This in practice initially did not work and packing had to be

placed beneath the segment. The solution proved to be to increase the opening allowing the

interaction between the lower three segments and the tail shield to be minimized.Excavated material is being recycled for aggregate including the backfill for the annulus around the

segments. The coarseness of the crushed granite is not ideal for this function causing excessive wear

and difficulty in placing. The injection system has been moved forward from deck 6 to deck 2 to

reduce the wear.

The local labour force is not experienced in TBM work, while this was expected it has led to a

lengthened learning curve process. Robbins has put together a detailed training course which takes

the Contractors personnel through four stages of learning from general tunnelling to looking in

detail at electrical and hydraulic circuitry and studying the operation and maintenance manuals of

the equipment.

PROJECT UPDATEExcavation commenced on 19

thMay 2008. By mid March 2009 the first TBM had achieved over

2,500m of its predicted 22.5km drive. Early difficulties with the geology had been expected as well

as the learning curve for training local personnel in the operation and maintenance of the TBM and

conveyor systems. Following a three week stoppage in January 2009 to replace a cracked main

bearing seal progress has improved with all the best day, week and months so far being achieved in

the first quarter of 2009. Excavation outputs up to the 12th

March 2009 are given in Figure 7.

Modifications to the TBM and conveyor systems to deal with the blocky ground and groundwater

have been made and are proving effective. Excavation rates are expected to increase significantly in

2009.

Production Records at 12th

March 2009

Best calendar month 401.85

Best Payment period month 423.53

Best Day 27.03

Best Week 117.05

12d

ays

5/08 6/08 7/08 8/08 9/08 10/08 11/08 12/08 1/09 2/09 3/09

Figure 7 Monthly progress for first 10 months

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CONCLUSIONS

The OFTA method can be used on any TBM type at any diameter, though it is best suited to the

larger diameter projects. In 2008 Robbins also completed the assembly of the 12.4m diameter Main

Beam TBM for the Jinping-II Hydroelectric Project. The jobsite, located in a remote area of

Chinas Sichuan Province, requires that most components be shipped via barge on the nearbyYalong River (a tributary of the Yangtze). The OFTA process allowed for decreased shipping costs

and shipping risks since the assembly was achieved during the high water season of the Yangtze,

where the barges could be used. At other times the TBM components would have required road

transport utilizing very expensive heavy

haulage equipment.

At the end of 2008 Robbins had orders for

several future machines which will utilize

OFTA. The second AMR TBM and the

Veligonda Tunnel No. 2 machine discussed

above; The 12km long 10.0m diameter EPB

TBM Sleemanabad Carrier Canal tunnel inMadhya Pradesh, India; and a 9.59m

diameter EPB TBM for the 6.2km long

Mexico City Metros Line 12. The OFTA

approach is being considered in all Robbins

future machine proposals.

Future developments utilizing 4D graphics

(3D assembly animation linked to a

programme timeline) that will allow greater

levels of planning and control of the OFTA

process are currently being planned.

ACKNOWLEDGEMENTS

The authors would like to thank the AMR site team, especially Jim Clark and Bill Brundan, for their

photographs, input and updates on the project.

REFERENCES

Willis, D. (2008), Robbins TBM Assembly Method Fits Up with Tight Schedules, The Robbins Company press

release.

Willis, D. (2008), Robbins TBMs Excavate Indias water tunnels, The Robbins Company press release.

Figure 8 The AMR project team