Home Articles New INDIA’S GRAND VISION -The Tunnel of Hope Delivered The Chenani-Nashri tunnel

INDIA’S GRAND VISION -The Tunnel of Hope Delivered The Chenani-Nashri tunnel

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End to a Himalayan Ordeal

 

Chenani-Nashri tunnel

 

Yes! Try travelling on National Highway 1A (NH 1A) in north India to know what a Himalayan Ordeal is. It is only when you are on those single lane, narrow winding roads that negotiate perhaps some of the steepest and most treacherous terrain on the pla-net, you truly are convinced that its doomsday. The grueling course takes a much harder stance when you need to navigate a 288km journey between the cities of Srinagar and Jammu. Besides the unfathomable dangers you are also treated to a slow moving traffic and multiple traffic jams.(see Figure1 fatal twists & suicidal turns).

 

Figure1 fatal twists & suicidal turns

 

 

Thankfully a solution came up to upgrade this stretch of the NH 1A to render it into a safe , fast-paced 365 day usable highway. – The Chenani-Nashri tunnel Tunnel.

This story covers the following areas:

– Chenani-Nashri tunnel Project specifics
– Tunneling Operations
– J&K’s own issues that delay projects
– The Formidable Himalayan Challenge
– What makes the Himalayas technically toughest to tunnel?
– Choice of techniques and reliability of investigations
– The future – The Tunnel Advantage

The Great Connect – Patnitop Tunnel

Prime Minister Narendra Modi dedicated to the nation on April 2, 2017, Jammu and Kashmir’s Chenani-Nashri tunnel, which has become South Asia’s longest road tunnel and the fastest in the country. India has put in commission an Engineering marvel which has unique features and a feat achieved in most trying terrain and work environment. ( See Figure 12 & 13)

 

 

The challenging construction of India’s largest road tunnel is part of a vital project in connecting inaccessible regions in a globally safe and fast pace is a remarkable feat especially when it also is technologically most advanced ‘state of art’ in construction as well as systems.

The tunnel which runs from Chenani to Nashri is also considered the ‘safest’ tunnel in the country, with provisions to ensure the safety of passengers from fire incidents and collision inside it. The 10.89 km long tunnel is a part of the Jammu-Srinagar Highway’s four-laning project and will reduce the distance between Udhampur district’s Chenani and Ramban’s Nashri from 41 km to just 10.89 km, which can be covered in just 10 minutes instead of the two and a half hours usually required. The tunnel re-duces travelling distance between the two points to 10.89 kms as it by-passes Kud-Patnitop-Batote circuit. (See Figure 2 &3)

 

 

The tunnel will act as an alternative to the existing NH1A section, which faces geometrics and safety concerns, as it passes through steep mountain terrains. It will by-pass the ecologically sensitive Patnitop area, while also steering clear of 44 avalanche and landslide prone spots on the highway.

The highway remains closed for 40 days a year due to bad weather conditions. Therefore this two-line bi-directional traffic tunnel will be an all-weather and reliable road throughout the year, safe, fast, user friendly. This state-of-the-art tunnel will also have parking spots in case of vehicle breakdowns

The work on the construction of 9.2 kilometers tunnels, connecting Udhampur district with Ramban district on Jammu-Srinagar Highway, was started on May 23, 2011. The initial completion period of the project was planned as five-year but got extended by 2 years.

The work initially got delayed due to dispute between construction workers and executing agency and then inclement weather conditions particularly heavy snowfall, flash floods, landslides and 2014 floods played spoiler too.

The construction, involved nearly 1,500 engineers, geologists and labourers, besides skilled workers. The National Highway Authority of India has spent Rs 3,720 crore on the project which has two tubes: the main tunnel and the escape tunnel. These two are internally connected through 29 cross passages.

See Project Sheet 1 & Figure2 Tunnel Principal Data that provide all Project Techno economic & conservation information

Work on four laning of Udhampur Chenani and Nashri-Ramban stretches of the highway started is still underway.

Project Sheet 1

Chenani Nashri Road Tunnel Project

Patnitop tunnel project specifics

The project involves construction of a single-tube, two lane main tunnel of 13.3m diameter along with a 5m diameter escape tunnel running parallel to it.

The main tunnel will be connected to the escape tunnel through pedestrian and vehicular emergency cross passages at every 300m and 1,200m respectively. It will run in the lower Himalayan mountain range to connect Chenani to Nashri villages.

The horseshoe-shaped tunnel will bypass the four-lane Udhampur to Ramban Section of NH-1A and have two rotary junctions. It will cross through the flyshoid geological formation in the Patnitop range of the Himalayas.

The tunnel has a maximum overburden of 1,050m. The tunnel will reduce the elevation and hairpin bends associated with the existing highway. The gradient will also be reduced from 4.5% to about 0.5%.

Construction of the Chenani-Nashri tunnel

Construction uses New Austrian Tunnelling method (NATM) technique. Under NATM, the tunnel is sequentially excavated and supported.

The project is of complex nature as it involves cutting of the Himalayan rocks. Advanced tunnelling and drilling equipment are being used for the project.

Construction of the tunnel began in September 2011 and opened on 2 April, 2017

The remote location of the tunnel in the mountain ranges, geology and logistic constraints raise several engineering and management challenges to the contractors.

Trinitrotoluene (TNT) explosions were used during the initial phase of tunnel construction through the hills.

The works included overall construction of a 10.9km highway. It will include the 9km tunnel, a 50m single span bridge at north portal of the tunnel and a 40m single span approaching bridge at the south portal.

The south section also requires surface works of 1.3km, while the north approaching portal requires 0.6km of embankments and slope cuttings. Other infrastructure will include technological and service buildings, toll plazas, other project facilities and soil dump areas.

Project Financing, SPV and Main-Contrac-tors involved

IL&FS Transportation Networks (ITNL) was selected for four-laning of the 41km NH1A highway (from 89km to 130km, which includes the Chenani-Nashri tunnel) on design, build, finance and operation basis in May 2010.

The concessionaire will receive annuity from the National Highways Authority of India (NHAI) for 20 years. ITNL established a special purpose vehicle Chenani Nashri Tunne-lway (CNTL) for execution of the project.

The project is being funded by a consortium of 12 banks led by the State Bank of India, Project Finance Strategic Business Unit.

Feasibility studies for the highway upgrade projects were conducted by NHIA and Louis Berger Group during 2006 and 2007. D2 Consult Prague was a sub-consultant.

ITNL awarded about $570m engineering, procurement and construction lump sum, fixed price contract to Leighton Welspun Contractors for the Patnitop tunnel project in July 2010.

Scope of the contract includes architectural, structural, civil, electrical and mecha-nical works, SCADA, lighting and ventilation, fire protection, traffic control, video surveillance, emergency call and communications works.

The Main Contractor was later replaced by Sub contractors when Leighton quit. This is detailed later when focusing on J&K Projects Road Blocks.

GEODATA was to provide the detailed design and construction supervision for the project.

Note: See also Contract data at close out summarized at the end.

SYSTEMS ENGINEERING ASPECTS

Hailed as an engineering marvel, this marks significant roadbuilding firsts in India, including an unprecedented stress on user safety and is not only India’s largest highway tunnel but also most intelligent one in the world.

Amongst its host of intelligent road tunnel features are:

1. Integrated traffic control system
2. Entrance Detection Control System
3. Active Firefighting System
4. Electronic Surveillance System
5. Evacuative Broadcast System
6. Tunnel Ventilation System

Significant features like Integrated Traffic Control System (ITCS), Video surveillance through 140 CCTVs, wireless communication and FM broadcast system, Entrance Detection Control, Electrical Fire signalling, Active Fire Fighting, Tunnel Ventilation, Evacuative Broadcast system and SOS call boxes make it most intelligent tunnel of the world

With the help of cross passages after every 300 meters, which lead to escape tunnel and through public address system or FM announcement, the evacuation of humans in case of

– any incident inside the main tunnel will be done within 90 seconds
– while in the second phase, the situation will be diffused in the next 90 seconds
– thus finishing the entire operation within three-four minutes.

Besides, there are SOS Call Boxes at every 150 meters inside the main tunnel, where immediate requirements such as first- aid kit are installed and the person on very entering the box will automatically get connected with control room for further instructions as well as inviting swift action by Route Patrolling Officers.

Thus, this state of the art engineering marvel in the most difficult terrain of Himalayas is fully automatic smart system control tunnel with no human intervention for the technical operation.

>> Ventilation

“Even as world class safety measures and fully integrated control system without human intervention are also installed in a few tunnels in the world, the fully transverse ventilation system in Chenani-Nashri tunnel makes its most intelligent and confines the incident within 100 meters unlike other tunnels,” said Ashutosh Chandwar, vice-president of Project Developer IL&FS Transport Network, while briefing media persons on visit to the tunnel.

Further, he added, in case of increased Carbon Mono-oxide and opacity level inside the tunnel, the sensors will automatically restore the ventilation system by opening fresh air and exhaust windows in the particular area.

With inlets every 8 metres bringing fresh air into the main tube, and exhaust outlets every 100 meter opening into the escape tube, the longest highway tunnel in India also happens to be Asia’s longest bi-directional highway tunnel with fully transverse ventilation system. Such a ventilation system is a first for India.

For such long tunnels, ventilation systems are essential to maintain clean air, permissible carbon dioxide levels and expel harmful vehicle emissions. In layman parlance, the drives for ventilation system are akin to the lungs and the motors and safety software akin the muscles for the tunnel ventilation system.

To ensure smooth travel and safety of commuters, ABB designed, engineered and supplied low harmonics variable speed drive (VSD) system for tunnel ventilation.

The VSDs and motors are installed at the North (Nashri) and South (Chenani) portals for air supply and exhaust. “ABB India is privileged to deploy technology for another infrastructure project of national importance.

ABB’s best in class global technology manufactured in India will make Asia’s longest road tunnel safer and will ensure effec-tive ventilation,” Sanjeev Sharma, CEO and Managing Director, ABB India, says . “The new tunnel’s safety controls were developed by ABB in India, for effectively mitigating any fire emergencies.

“Globally, ABB has executed the world’s most powerful ventilation system with the power of 80 Formula E cars for Gotthard Base Tunnel in Switzerland+ – the world’s longest (35.5 miles) and deepest (8,000 feet maximum depth) train tunnel.

>> SAFETY

Infrastructure Leasing and Financial Services (IL&FS) Company is all set to handover the project to the NHAI now that the focal inauguration by the Prime Minister has taken place.

The company says the tunnel has unprecedented safety features, a key feature being the two tubes that run parallel to each other.

The main traffic tunnel is 13 metres in diameter and has a safety tunnel alongside that’s about 6 metres in diameter.

The two 9-kilometre-long tubes are connected by 29 cross passages at regular intervals along the entire length of the tunnel. These 29 cross passages between the two tunnels will be used to evacuate a user who might be in distress, or to tow away a vehicle that might have broken down.

124 cameras and a linear heat detection system inside the tunnel will alert an Integrated Tunnel Control Room (ITCR) lo-cated outisde to monitor and intervene, if necessary.

Commuters will also be able to use their mobile phones inside the tunnel. BSNL, Airtel and Idea have set up facilities inside the tunnel to carry signals.

TUNNEL ECONOMIC IMPACT

Cars will pay ` 55 on one- way fare and ` 85 for to-and-fro journey and ` 1,870 for a ‘monthly pass’, while bigger vehicles like pick-up and small buses will have to pay ` 90 for one-way and ` 135 for to-and-fro toll. Buses and trucks will be charged ` 190 for a single journey and ` 285 for return.

“The tunnel has multiple economic gains as connectivity in the remote area can help transform the life of this neglected region in the hills.

 

 

The credit goes to previous planners for having mooted this tunnel,” says S P Singh, senior fellow at the Indian Foundation of Transport Research and Training (IFTRT)

No one wants to be Forever Delayed. It takes ten hours or more to transport a load of fruit or vegetables grown in the Srinagar Valley to Jammu via NH 1A, the Valley’s only link to the Indian market southward. The Traffic jams up at each bend and tailbacks are long on the straights as motorists have to wait in line to pass the numerous Tata trucks typical of the Jammu and Kashmir region.

These trucks are slow as they strain on the mountain grades, their drivers pulling hard on their steering wheels through each tight bend, while other vehicles try to pass, often dangerously close.

The new twin-tube tunnel from Chenani to Nashri will go a long way to relieving these bottlenecks and make the journey both shorter and considerably safer. Of the difference the Chenani-Nashri twin-tube tunnel, within the overall NH 1A upgrade, will make, local truck driver Mushtaq Ali says, “It will save us enormous time, about 250 rupees (US$4.10) in fuel, and in vehicle wear and tear. It will also relieve several bottlenecks on each TRIP.”

Of the economic and social impact the completed overall NH 1A upgrade will have, Debabrata Sain, Atlas Copco’s India marketing manager, says, “The 288km distance between Jammu and Srinagar will be reduced to 238k, but more importantly the 12-hour journey will be covered in about five hours, avoiding perilous points such as Khooni Nala, known as bloody path, where shooting stones slide at the speed of a bullet taking a heavy toll on lives. The tunnels will also end the snow-related traffic jams that last several days.”

Sain said shorter travelling distances within Jammu and Kashmir and on to further destinations will save individual citizen and business vehicle fuel costs, vehicle wear and tear costs, and, at the same time, reduce environmental pollution through lower carbon emissions. “There will be other benefits such as increased commerce and tourism, more employment for local people, and skill development among local youths,” he adds.

 

 

10. In case a vehicle breaks down, this state-of-the-art tunnel will also have parking locations.

Typical J&K Infra Projects Problems

There is no dearth of efforts and resources put in to derive best results. The Chenani- Nashri Tunnel is a case in point. On July 14, 2015 Transport Minister Nitin Gadkari was witness to a rare engineering feat digging of a nine km road tunnel, the country’s longest, between Chenani and Nashri in Jammu & Kashmir.

But the project, despite all efforts has not gone off without hiccups and seen a 2 year delayed completion. In October 2014, Australia’s Leighton Contractors backed out after Mumbai based IL&FS Transportation Network refused to pay more. “Leighton had agreed to take up the project for a lump sum. The workers went on a strike demanding higher wages.

The difficulty was aggravated after floods in September 2014 closed the national highway for a month.

Leighton raised excess bills and later withdrew,” says an official of IL&FS. For IL&FS, it was a big challenge. “IL&FS then hired subcontractors. The work went on smoothly then onwards with the project opening on 2 April 2017.

The ` 3,800crore tunnel is symptomatic of problems that most big infrastructure projects in the state are facing.

While some, such as acquisition of land, lack of funds, delay in clearances and labour issues, are common to all the states, in Jammu & Kashmir, difficult terrain is proving to be an additional stumbling block.

Besides IL&FS, Hindustan Construction Company (HCC), Ramkay Infrastructure, GVK and Jaiprakash (JP) Associates, which are implementing some landmark projects, are also facing difficulties.

As most of these projects are in road and power sectors, this is also hitting the state’s economy as industries grapple with power cuts and spend more to transport goods due to lack of high quality road infrastructure.

The Infra Deficit

The only road that connects Kashmir with other parts of the country is the Jammu Srinagar national highway. It is blocked in winter due to landslides. Government estimates reveal shortage of 3,000km roads in the Kashmir division to build them over `3,000 crore is needed.

The Power Development Department (PDD) figures show that the state faces a power deficit of 27 per cent during peak hours. The situation has not improved much over the years. And given the mess the new projects are in, it is unlikely to do so in the near future either.

Also, Kashmir is still not connected with the country’s railway network. The Jammu-Udhampur-Srinagar-Baramulla line has been delayed by years. The plan for connecting Kashmir with the rest of the country was mooted in 1994. It was supposed to be completed by August 15, 2007. However, work on major stretches of this 345km line is still incomplete.

These include the 110km section bet-ween Katra and Banihal. The latest target date is now December 2020. Within Kashmir, the 18km section between Qazigund and Anantnag was completed in October 2009. The railways also opened the Banihal-Qazigund section in June 2013.

Several projects since then are on anvil though.

A glance at the tunneling operations

“Tunnelling in the Himalayas is difficult and so the Chenani-Nashri tunnel no exception. The mix of geological formations lead to a lot of distressing and cracking of the rock mass – it’s full of surprises(See Figures 14 to 21). See more specifics in section on “ The formidable Himalayan Challenge”.

 

 

The Chenani-Nashri tunnel contract was awarded on an EPC (Engineering, Procurement & Construction) basis. Using a fleet of seven Atlas Copco drill rigs, the Chenani-Nashri tunnel has been excavated according to the NATM (New Austrian Tunnelling Method).The fleet included four Boomer XE3 C rigs with ABC Total (fully automatic) and three Boomer E2 C rigs with ABC Regular (semi-automatic).

The project concessionaire is a subsidiary of one of India s largest private sector BOT (build-operate-transfer) road operators, developing designing, operating, maintaining and facilitating surface transportation infrastructure projects in 18 states in India and also is present in atleast four other countries.

The inhomogeneous rock at the tunnel site includes only 26m² of loose ground. There is 506m² of stable ground, 3,428m² of slightly overbreaking ground, 1,411m² of friable and 2,504m² of heavily friable ground, and 673m² of pressure exerting and 435m² of heavy pressure exerting ground.

The tunnel enters and exits the mountain at an elevation of 1,200m, the finished dimensions are 14m wide and 10m high. The escape tunnel is smaller, at 6x6m alongside the main tunnel .

The lead contractor is using Atlas Copco Häggloader 10HR-B loaders for mucking out into 35 tonne trucks. Cross passages connect the main tunnel to the escape tunnel every 300m for pedestrians and every 1,200m for emergency vehicles. The rock in this region consists mostly of sandy shale, mudstone, siltstone and soft sandstone, and drilling precision is of the utmost importance to avoid the extra costs associated with underbreak or overbreak. This becomes possible with automated features of the Atlas Copco rigs being used.

In these projects productivity & progress are directly dependent mainly on one factor; And that is the pace of your face drilling rigs. In otherwords if the rigs stop, then it means the entire operations stop. Productivity plunges and the whole cascading effect of delay, operation cost rise and salvaging assets follows.

Therefore it is imperative to make best geological investigation, rightly be able to pinpoint the technique and equipment. In this endeavor a lot now a days is dependent on automation level and software in use, which together enable the contractor to be as close to reality as possible during tunneling operations. The Agencies on work can keep verifying by drill checks if what they are going to encounter is in line with forecasted by investigation reports.

A typical example is the Measure While-Drilling (MWD) function on the Boomer XE3 C. these features help in probing and ascertaining efficacy of preliminary investigation geological data utilized for project estimates & techniques.

For instance, this rig was used at the South Portal to verify if it showed same as what was expected to be found in the rock mass. Since the escape tunnel runs ahead of the main tunnel so the rig is used for probe drilling that is to check to see that the rock ahead is the same as anticipated.

Lasers are used to position the rigs at the face. Two alignment plates are mounted on a rig’s boom. When the red laser beam passes through the plates, the boom is parallel to the laser at a known offset.

Training in advance is essential before being operational on-site. Copco Boomer drill rig simulator is a training platform..A proficient single two-boom Boomer E2 C operator can set one boom in place, start drilling, and then turn his attention to the second boom, continuing back and forth throughout the round.

These operators can drill 100 holes over the 42m² escape tunnel face in just 90 minutes.

The Boomer XE3 C with ABC Total drills the 76m² main heading with its drill pattern of 152 blast holes in one hour 45 minutes.

The main tunnel excavation is in two levels with the Boomer XE3 C covering the 6m top heading as well as 4m split bench. Excavation of the escape tunnel is advanced 200m ahead of the main tunnel and the Boomer E2 C drills the whole face. Blasted rounds vary ranging from 2.5m to 4m.

Rock support is used to assist natural rock convergence which must be less than two millimeter per month.

Reinforcement consists of two rows of 5m Atlas Copco Swellex PM24 rock bolts, eight in one row and nine in the next. The rows are spaced 2.5m apart where no convergence is noted. Where convergence is noted, the rows are 2m apart.

The rock-bolt holes are drilled with the same 51mm bit used for the blastholes. Two bolts are installed in the benches, one on each side. In the escape tunnel, 5m Swellex PM24 bolts are installed in two rows, the first row with six bolts and the second with seven.

Fibre-reinforced shotcrete is applied in two overlapping stages to a thickness of at least 15cm. The first 5cm is applied immediately after bolting. Setup time is fast enough to provide almost immediate support.

As one contractor puts it, with proper scaling and bolting, the 5cm fibre-reinforced shot-crete enables them to progress at a good pace safely, saving them the extra step of bolting up mesh.

The second layer of 10cm shotcrete overlaps the initial 5cm shotcreting during the next advance and provides the necessary support until the permanent lining is installed.

A state of minimum convergence has to be achieved. With the technique followed convergence during excavation was kept to a minimum without compromising on safety or progress. Lattice girders are used wherever movement is anticipated and will become an integrated part of the final tunnel lining.

Right number of shotcrete machines and Boomers need to be available dedicatedly to avoid fall in productivity. In this case, Normet 7110 shotcrete machines and a Boomer E2C underground drill for a period of six to 12 months were at disposal at all times.

In the course of the Chenani-Nashri tunnel project, a total of 60,000 Atlas Copco Swellex bolts have been supplied for rock bolting

Project Completion Data Summarization

Near or at the project close out stage it is necessary to recapitulate the actual status in terms of ‘As delivered on ground’ with the changes or variations that had to be made during currency in terms of agencies/contractors, parameters or goals that had to be changed for information, record and an assessment of how much the original decisions have varied to be useful for future decision making.

(see Figures 22 to 27 of nearing completion and testing)

 

 

>>Tunnel Alignment

Patnitop Tunnel is designed as a base Tunnel. Passing under the Patnitop mountain range with overburden more than 1 Km and belongs to NHDP Phase- II. The contract package starts at existing road from Km 89 and ends at Km 130 of existing road.

Tunnel mined portals are located at approx. start of Km 90 (southern portal) close to village of Chenani and Km 130 (northern portal) close to township of Batote of existing road at elevations 1230 m and 1210 m respectively.

Tunnel profile grade is of a roof character with 0.5 % longitudinal profile grade. Tunnel horizontal alignment starts and ends with curves of 300 m radius, and the rest of mid-section is straight.

Main Tunnel direction is South to North. Travel distance will be reduced for more than 30 Km and climbing and descending of approx. 1000 m shall be avoided. Tunnel shall be 2-lane, bidirectional tunnel with parallel escape Tunnel and cross connections into escape Tunnel for emergency exit.

The Existing road (2-lane, bidirectional) will be utilized to accommodate the local traffic in the area as well as over-sized and other vehicles non-suitable for tunnel operation. The existing carriageway will be upgraded with minor improvement to both the horizontal and vertical alignment.

 

 

>> Project Assignment

BACKGROUND

NHAI appointed the Louis Berger Group, Inc., USA, in Joint Venture with LRP Consultants, India and in association with L&T Ramboll, India, as consultant to carry out the Feasibility Study and DPR for 4-Laning of the section Udhampur to Banihal, Km. 66 to Km 188 of NH-1A in the State of Jammu and Kashmir. The Complete project length is divided into 5 packages.

Independent Engineer IE for project management including quality assurance was .M/s Euroestudios.S.L in Association with M/s Segmental Consulting and Infrastructure Advisory (Pvt.) Ltd.

Role And Functions of IE

The role of IE as in schedule “Q” of Concession Agreement between NHAI and CNTL (SPV created by IL&FS) the main points are described below:

– Review of Drawings & Documents.
– Review, Inspection and Monitoring of construction work.
– Conducting testing on completion of construction & issuing completion/ provisional certificate.
– Review, Inspection & Monitoring of Divestment requirements.
– Determining as required under the Agreement, the costs of any works or services and / or their reasonableness.
– Determining, as required under the Agreement, the period or any extension thereof, for performing any duty or obligation.
– Assisting the parties in resolution of disputes.
– Undertaking all other duties and functions in accordance with Agreement.

Agreement was drawn by NATIONAL HIGHWAY AUTHORITY OF INDIA (NHAI) with Chenani

Nashri Tunnel way Limited. (CNTL) on 28th July 2010. For this project IL&FS Transportation

Networks Ltd has formed a Special Purpose Vehicle (SPV) by the name of Chenani Nashri Tunnelway Limited (CNTL) (hereinafter referred as the “Concessionaire”).

>> Executing Agencies and Contract Data

AGENCIES

Developer: M/s IL & FS Transportation Networks Ltd is the Developer.

Concessionaire:

SPV created in the name of M/s CNTL for this Project. CNTL is the Concessionaire for this project; CNTL mobilized staff and established its office C/o Lower Mada Village Gujjard Tehsil Chenani Distt. Udhampur. .

EPC Contractor:

M/s ITNL demobilized ORIGINAL contractor M/s Leighton.Project highway and tunnel activities is divided into three section and contractor has deployed the separate construction for following sections.

Section 1: Excavation Works From North Portal-M/s AIMPL-BCC(JV).

Excavation Works From South Portal-M/s Nagyan Construction.

Section 2: Lining Works South Portal: M/s New India Infra Build tech Pvt. Ltd.

Lining Works North Portal: M/s Savronik- BCC (JV).

Section 3: Surface Works: M/s Vinay Construction, M/s Chudhary Construction & M/s Kamlashi Construction.

INAUGURATION

– Escape Tunnel (South Portal) First blast taken on 8th August 2011
– Main Tunnel (South Portal) First blast taken on 18th August 2011
– Escape Tunnel (North Portal) First blast taken on 8th October 2011
– Main Tunnel (North Portal) First blast taken on 22nd October 2011

TUNNEL´S BREAK THROUGHS

– Escape Tunnel 2nd June 2014
– Main Tunnel 13th July 2015

DELIVERY

All technical requirements have been met in delivery.

Despite change to Main Contractor the work continued by packages splitting (as earlier briefed in the article on this and inclement weather delays).

The project was dedicated to the nation as already said by PM Modi on 2 April,2017.

The formidable Himalayan Challenge

From the tunnelling view point, the Himalayas have the most challenging ground conditions almost anywhere in the world. The main reason for this is that the Himalayas are the youngest of the mountain chains. They are demonstrably rising faster than anywhere else. Their composition is also younger generally, and this makes them much less consolidated than older fold belts. This agrees with the fact that they are one of the most active of the plate margin zones, rising at a rate that is almost double that of the Andes, which, in turn is almost three times that of the Alps(see Figure 28).

Such an active ‘stress’ scale as in Himalayas cannot be found anywhere else in the world except perhaps the around the Pacific Ring of Fire. Stress levels are greatly dependent on geologic age and therefore the younger the mountain belts the more imbalanced is the stress state.

As a result, stress conditions (magnitude and variation) can be potentially more extreme and adverse on a Himalayan tunnelling project than even has been encountered in some of the worst sub-mountain tunnel drives, including the Olmos and Yacambu Tunnels of Peru and Venezuela respectively, which are landmark projects from the bursting and squeezing perspective.

Now therefore we come to the crux of the matter, which is How Dangerous are the Himalayas as compared to the Rest of the World Ranges?

The answer in terms of tunneling difficulty levels can be as follows starting with highest difficulty level as no.1. Thus a tunnelling difficulty ranking scale for the mountain chains of the world can be classified as:

1. The Himalayas, arguably the most difficult and challenging;
2. The Andes;
3. The Alps, through to the least difficult of the main chains;

Then come the Rockies and the Western Cordillera, at 5, 6, 7 corresponding to older mountain cores with the Canadian & Scandinavian Archean, Algonquin and Adirondack age mountain belts which can be considered almost totally benign stress-wise.

The above ranking scale is based on tunneling experience and encounters and can be therefore relied upon. Literature reference shows the Andean tunnels traversed much worse ground conditions and met greater geotechnical challenges than were encountered anywhere along the 50km+ length of Lötschberg and St Gotthard deep Alpine railway tunnel drives in Switzerland.

While there has been escalated TBM use in excavation of deep rock tunnels with aims of fast paced progress a caution needs to be exercised on where to avoid TBMs. It should be kept in mind that adverse geology can throw up problems, actually resulting in huge delays and cost increases for either drill+blast or TBM use, especially, when significant depths are involved.

One thing that can be surmised is that for almost all projects that have suffered geotechnical difficulties the cause has been inadequate forecasting.

Adverse faults and challenging zones of poor ground do occur in old mountain ranges too but the critical over ruling difference is in the matter of the stress state.

On ‘active’ stress state basis, a similar length deep tunnel excavations under the Himalayas will pose significantly more challenges than an equal length, equal cover drive almost anywhere else in the world.

Going for NATM is prudent because the reageological problem conditions, which might be tractable at shallow depth, with either TBMs or drill+blast approaches, when encountered at significant depth (>1000m) can prove disastrous depending on stress state, rock competence and prevailing groundwater inflows.

The fact that within the Himalayas, conditions can be expected to be as bad as has ever been encountered elsewhere, means that there has to be the ability, during the tunneling process itself, to have allowance for changes to be made of driving method and support approaches.

It is this factor of need to adopt flexible solutions imposes the constraints to TBM usage as the rigidity of design elements incorporated into the fabrication of a typical TBM restrains any operational flexibility. As a result, in case of an adverse situation there could be case of entrapping or damaging the TBM.

Problematic geotechnical conditions

Two issues, essentially, control the ability to successfully improve tunnelling effec-tiveness for traversing through the characteristically complicated ground conditions found beneath the mountainous regions of the world.

These are:

– The influence of adverse geotechnics, centred on the ability to deal with difficult ground conditions created by stress state, groundwater conditions and/or prevailing rock quality, and
– The limitations of current tunnelling technology ranging from drill + blast and NATM methods through to various TBM types.

Tunnelling in the Himalayas, the Andes, and until recently, the Alps, avoids TBM use due to perceived inflexibility, and the high likelihood of them getting trapped by adverse ground conditions, either as a result of squeezing or spalling/bursting conditions or because of ground collapses associated with rockfalls or with running or flowing ground within faults, always in these cases complicated by heavy water inflows (Fig 29).

Any of these situations can lead to problematic tunnelling at best, and at worst collapses and abandonment. Dealing with such problems is always challenging, but is ten times worse when the tunnel heading is 10km from the nearest portal, as is the case in many TBM drives.

Though such conditions can be problematic conventional drill+blast and NATM methods as for a modern machine drive is often ignored.

Geotechnical considerations

Three main geotechnical elements control the ability to execute trouble free tunnels at significant depth. These are stress state, groundwater conditions and the rock itself.

Adverse characteristics of any one of these three elements can, on its own, compromise drill+blast or TBM tunnelling, but it usually takes a combination of all three being adverse to trap a machine or halt a drill+blast drive, to the extent that a bypass becomes necessary (see Fig 30). Methods to characterize each, at least at an overview level of assessment exist (Methods for characterizing rockmass conditions for deep tunnels are briefly examined in a recent paper by Verman et al).

 

 

Unfortunately it is always at an early stage in a project that decisions about excavation method are needed. Almost always, also, there is inadequate definition of stress state, rock competence and groundwater for most of the tunnel. Estimating conditions in the zones considered as most geologically problematic, therefore, becomes the focus for minimizing risk and maximizing objectivity for decision-making.

Decisions on whether or not to use a TBM for example, remains therefore a matter of judgment with the two most difficult questions being how much of the tunnel length is problematic? and how much of this problematic length is of critical concern?

The best possible geological assessment of likely conditions along a planned alignment coupled with application of nume-rical and analytical techniques to back-analyze similar conditions and assess applicability is the only right way to success.

Project risk

Investigating the tunnel alignment of deep mountain tunnels is a great challenge because it becomes cost prohibitive since like urban areas, boreholes on 50m centres or closer along the alignment cannot be done on mountains. This leads to dependence on getting best possible data on geological conditions at depth and along the alignment.

“On the scale of typical project risk reduction (Fig 31) from even for the most heavily investigated of deep tunnels (the Lötschberg and Gotthard Baseline tunnel alignments in Switzerland) only 20-30% understanding of what was finally known was available at the time when decisions were already having to be made about drill+blast versus TBM and with respect to TBM type selection.

 

 

This possible 70% lack of understanding, arguably led to some of the problems that were ultimately encountered. But these, given the length of the tunnels, were quite minor as a percentage, affecting less than 5% of the length and only a small fraction of the total cost “(A. Moergeli, Risk management in action – controlling difficult ground by innovation, RETC 2005).

Plotting on a conceptual graph (Fig 31) suggests that probably significantly greater than 50% risk reduction had been achieved by the site investigations.

The importance of focused site investigation cannot be over-emphasized as it is upon the data acquired from the investigation that the decision must be made between drill+blast or TBM excavation, and about what type of TBM to use, if a machine drive is selected.

Back analysis of case records

Many case records of difficult tunnelling through complex ground conditions in mountainous areas, particularly associated with faults and often with mud and debris inflows, have been reported down through the history of mountain tunnelling.

Case records dating back to the turn of the previous century indicate the extensive use of bypass tunnels to navigate around the most difficult fault zones. In fact, review of many documented cases suggests that for a large percentage no forecasting was available before the collapse because the area was not investigated. This was often be-cause cover was too great or access difficulties prevented drilling to the tunnel horizon or because of contractual arrangements.

Turnkey and EPC (engineer-procure-construct) contracts, of recent times for example, have shown lack of comprehensive investigation compared with most typical owner-administered contracts earlier entered into .

One common factor is delayed progress through difficult ground. The Amsteg fault zone collapse and subsequent entrapment of the TBM on the west drive of the Gotthard Baseline Tunnel drives in Switzerland, while the TBM on the parallel east drive passed through the zone with only minimal difficulty, can be partially attributed to rate of advance issues.

 

 

Several recent TBM problems that have developed in bad ground in Himalayan tunnels have occurred also when production advance was delayed due to holidays and/or maintenance shutdowns.

It is an amazing fact though, that even after the tunnelling industry has executed hundreds of kilometres of tunnels and endured numerous collapses, the majority of which have led to significant delays and often serious cost implications for the projects, inadequate forecasting of future conditions still emerges as a clear common thread for almost all cases.

Embarking on better planned, more extensive investigations holds the key to removing much current uncertainty regarding TBM effectiveness and success of drill+blast headings in certain rock conditions along any particular alignment. Under-standing rock mass behaviour and how different machines cope in different ground conditions is also key in stimulating innovative thought towards next generation im-provements in machine design, excavation processes and ground support systems.

The Tunnel Advantage

The connectivity need is paramount strategically and socio economically. There-fore India has to go full steam ahead with the ‘all weather’ protected means of access, now that it has established itself in the art of tunneling as no less than the best in technology by delivering one of the best tunnels in the world in most difficult technically challenging conditions. So wrapping up :

In Progress Road tunnels

Currently another 8.45km tunnel between Quazigund and Banihal on Jammu-Srinagar highway is also being constructed as part of INR100bn ($2.2bn) road projects in Jammu and Kashmir. This 8.45km QuazigundBanihal tunnel is scheduled for completion by March 2018.

While the ChennaiNashri connectivity is a single tunnel with 9.3 metre width and an escape tunnel for emergency, the Quazigund-Banihal stretch will have twin tubes with a width of seven metres each.

The two tunnels will also end traffic jam on NH1A due to heavy snowfall during winters and landslides in monsoons.

While the all weather tunnels will help traders transport fruits produced from this region to other parts of the country , it will also ensure seamless supply of essential items to the valley even during winter and rainy season.

This will also boost food processing industry in the region and generate jobs for locals.

At present, between October and January , Kashmir supplies at least 200 truckloads of apple every day to the rest of the country. The supply of pomegranates and other fruits is also significant from this region. It is widely believed that poor connectivity of Kashmir with the rest of the country has been a major impediment in the growth of the food processing industry in the state.

According to estimates, it also promises fuel savings of over Rs 27 lakh per day and will also provide better connectivity to people in Kishtwar, Doda and Bhaderwah in the Jammu region.

And Future Road Tunnels

Authorities are further planning to construct twelve other such tunnels to reduce the travel time and distance between Jammu and Srinagar from 293 km to 62 km and can be covered in a time estimate of 4-4.5 hours.

References: ibef, ILFS Reports, NHAI MPR & QPRs, BS, T.O.I, IE, Mining & Construction issues, Dr Trevor Carter papers as in text
Author’s Bio

 

Sadagopan Seshadri
Chief – Content Development,
CE – Infrastructure – Environment

The author leads our Delhi bureau. An Engineer and qualified ADR professional (NALSAR alumnus), Sadagopan Seshadri has been a senior Contract Management Pro-fessional in large national & Inter-national Companies. His domain experience is in Building Pro-ducts, Cement plants and Mega Power project execution. He has been an expert visiting faculty and univ. examiner for Contract Management at the SSAA, IP University, New Delhi. Being passionate about Environment Energy & Sustainability he has now turned to sustainable development Themes He is vocal with his views on these areas through his writings.

He can be reached at: design2xcel@gmail.com

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