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You might think that tunnels are always built by professionals, with an obvious and practical purpose — to transport people, to reach a deposit of coal or diamonds, to transport water, and so on. For some, however, digging a tunnel is a hobby, a distraction, an escape, a way of expanding their houses underground or even a way to exercise — we look at some of the tunnels built by ordinary people around the world. 1. Elton Macdonald
Adding capacity to the over-tasked wastewater system in Mexico City, an alignment through changing ground conditions is a likely candidate for Robbins’ Crossover TBM, Nicole Robinson reports.In the mountains northwest of Mexico City, the soft rock is self-supporting and very consolidated, a dream to mine. "Even the face is self-supporting," says Roberto Gonzalez, Robbins' general manager in Mexico. "You could use a normal backhoe and excavate like that. It's a beautiful ground to bore."But the alignment crosses valleys of tuff, faults and finishes with a stretch of soft ground with low cover. This is the scenario for Túnel Emisor Poniente II (TEP II), or the English translation of West Drainage Tunnel II.Conagua, Mexico's national water commission, is building the 5.9km-long tunnel with a 7m i.d. to reduce flooding in the area, and increase wastewater capacity. Across three municipalities, some 2.1 million people will benefit from the tunnel project.The contractor joint venture of Aldesa, Proacon and Recsa chose an 8.7m diameter, dual-mode type machine capable of "crossing over" between rock and EPB. With the August 2015 tunnel boring machine (TBM) launch on TEP II, manufacturer Robbins has supplied its first Crossover machine in Mexico.End gameRobbins draws comparisons to the Kargi Kizilirmak hydroelectric project in Central Turkey. The design of the TEP II machine was based largely on experience from past projects, and that TBM in particular. While initial reports on the Turkey project showed fractured hard rock, Robbins explains, within 80m of launch the geology became substantially more difficult than expected, consisting of blocky rock, sand, clays and water-bearing zones. The machine required multiple bypass tunnels and major modifications before it could resume excavation.Robbins says these modifications proved instrumental to the design of its Crossover TBMs, including the TEP II machine.In Mexico, the contractor JV expects to convert the machine from hard rock to EPB mode due to changing ground conditions in the last kilometre of the alignment. "Initially the proposal was a hard rock machine but they found they have 800m of water-more EPM conditions-that's the reason we proposed a Crossover," explains Javier Alcala, job site engineer for Robbins on TEP II.The ground conditions at TEP II are complex, from competent to weathered volcanic rock to clay, and sand. The final 800m is also the portion of the alignment with the lowest cover, some 12m, and the most populated. This is one of the reasons for using a Crossover machine. The rest of the drive has between 50-60m of cover on average with some stretches up to 150m."We try not to convert unless it's completely necessary because you stop, you have to drain the screw conveyor inside the machine, and you have to make a lot of changes, for example on the cutterhead," Robbins' Gonzalez explains.As an open mode machine boring in rock, the TBM is equipped in the event of entering running ground, he says. "These closure doors are able to maintain the material in the cutting chamber. They're just a safety." In smaller valleys of tuff there is potentially some water, but it's unknown for now, he explains."For these cases we believe that these closure doors will be held to see what we have to do with the material, if we have to consolidate in the front."Tight fitAldesa's Castillo says one of the biggest accomplishments on the project so far has been organising the logistics in such a small work space-fewer than 10,000 sq m. The JV excavated a 30m deep launch shaft supported by 800mm-thick Milan walls (slurry walls), and used on-site first time assembly, he says, to start excavation as soon as possible.Once assembled by gantry crane, the machine bored 100m before adding back gantries. When completely assembled the machine has nine gantries for a total length of 1,030m.At the time Tunnels & Tunnelling visited the project, the crews were still adjusting to having the full machine in operation, and had only recently started using the continuous conveyors for muck.The TBM was mining through a transition zone between tuffs and dacites, and had excavated 435m by mid November 2015. At the time of publication the TBM has bored 1,417.5m, which equates to 945 rings. The best day has seen an advancement of 42.8m and the best week is 185.1m. Robbins' Mexico office reports the TBM has reached softer geology and is boring very well.Tunnelling is expected to finish within this year and a second lining of reinforced concrete will be installed following excavation to extend the life of the tunnel. "Once we arrive to the final bit, it's a very close curve of 400m radius," Alcala explains.The tunnel alignment ends along the rivers of San Javier and Xochimanga in Atizapan de Zaragoza.
With a burgeoning market for hydropower development, tunnelling work is seeing an uptick in South America’s third largest country. Nicole Robinson looks at two recent projects.The World Bank released a report in 2010 to help the Peruvian government in assessing the potential role of hydropower in the energy sector and the measures that could be taken to encourage its continued development as appropriate. Hydropower has been the major source of electricity in Peru, traditionally supplying more than 80% of requirements, and serving as a source of independent generation for major mines and industries.However, as the report explains, in the early 1990s efforts turned to natural gas and the government began providing incentives for its use in power generation: "This resulted in a virtual moratorium on hydropower development as a result of the very low price of natural gas (below economic cost)."Over the next decade, with the development of export markets for gas and increased attention to the impacts of climate change, the Government returned its attention to hydropower. The Peruvian government completed its National Energy Plan 2014-2025, which calls for electricity to comprise 60% renewable sources by 2025, with 54% coming from hydropower.The International Hydropower Association called Peru a regional leader in small hydropower projects. In its 2015 Hydropower Status report it estimates Peru has hydropower potential of at least 70GW, "of which only 3.8GW have been tapped so far."In 2014 Peru added 199MW, ranking it among the top 20 countries installing capacity at number 17 —Canada comes in at number three and the US at number 16.The market potential for hydro construction in Peru has captivated the likes of Odebrecht, whose subsidiary Empresa de Generación Huallaga (EGH) is developing the 462MW Chaglla power plant, which will be country's third biggest hydropower project upon opening, scheduled for this year.Norwegian company Statkraft opened its ninth hydropower plant in Peru, the Cheves Hydropower Project, this autumn. "The opening of Cheves consolidates Statkraft's position among the largest power producers in Peru," says Statkraft's executive vice president of International Hydropower, Asbjørn Grundt. "It also underlines our ambition to further strengthen our position as a leading international provider of pure energy. Our efforts in South-America play a very important role in this strategy,"Chaglla’s bypassLocated between the districts of Chaglla and Chinchao, some 420m from Lima, the Chaglla Hydroelectric Power Plant has 406MW of installed capacity. The plant is the result of an investment made by Odebrecht Energia of $1.bn, with support from the Brazilian Development Bank, and the Inter-American Development Bank, among others.The project will also feature a small power house, including a power transformer with an output of 6MW. "Chaglla will be one of the largest hydroelectrical power plants in Peru and it will represent almost 8% of the current consumption of energy of this country," says Erlon Arfelli, manager of Odebrecht Energia in Peru.Construction started in May 2011, with Sandvik supplying six DT820-SC tunnelling jumbos for the excavation at Chaglla. Underground construction includes a spillway composed of three tunnels for a total length of 2,838m, 14.5m x 12.6m-high. The 14.7.km-long intake tunnel is horseshoe-shaped with a 7.6m diameter.One of the most important works in the project is bypassing the Huallaga River, which contractors performed through a trunk tunnel of 12.5m diameter, 1,125m long. Odebrecht says the work concluded nine months prior to the scheduled date. The bypass tunnel, a significant step for the project, allowing the dam to be constructed in the former riverbed.Odebrecht says EGH began filling the reservoir on September 1, 2015, and expects the process to last between 45 and 60 days. The project's lenders appointed Mott MacDonald in 2013 as independent engineer to monitor construction.
Work to upgrade the Farnworth tunnel as part of a route electrification project called for enlargement works, and led to the procurement of a UK-manufactured TBM. Ian Clarke, writing for the manufacturer, reports.Tunnel Engineering Services (TES) recently provided a specially designed tunnel boring machine (TBM) in support of the Network Rail route electrification project between Manchester and Preston via Bolton which when completed will electrify one of the North West's busiest routes and allow faster trains with more passenger space.As part of the construction works there was a requirement to reconstruct/enlarge the Farnworth Tunnel which is on the line about 4km southeast of Bolton. The reconstruction was required because the original tunnel size wouldn’t allow the installation of the new overhead power lines required by the new trains.As well as the tunnel rebuild, some 1,600m of track through the area also had to be lowered to ensure smooth running of the electrified rail line.ChallengesThe original tunnel was constructed in the mid-1830s and runs over a length of some 270m. The construction comprises a mix of brick and stone lining with stone portals through a mix of ground conditions.Prior to the electrification reconstruction works commencing, over 1,500 ground investigation bores were made to establish what ground types would need to be handled by the tunnelling machine during the excavation operation. After examining the market, TES was approached as the potential TBM manufacturer with a brief to design what ultimately proved to be the largest TBM ever constructed in the UK.The TBM, named Fillie, had to bore a new 270m-long tunnel, removing some 30,000t of material and install 1,940 concrete lining segments to complete the new tunnel. Work started at the site in March 2015 in preparation for the arrival of the TBM.Prior to works starting, construction of the TBM itself was something of a challenge. Having to excavate the original tunnel with its Victorian interlocked solid stone work, brick lining and the surrounding ground meant that the design had to be not only durable to enable the very hard stone work to be removed but also flexible enough to enable excavation unit changes relatively quickly and easily as the ground conditions changed during the tunnel advance.The location and proposed route of the new Farnworth Tunnel was such that it effectively required the removal of pretty much all of the existing tunnel alignment and also required the excavation for the new tunnel to, at times, pass very close to the original smaller diameter Farnworth (running) Tunnel that was built in the early 1830s. Because of these proximities it was decided that a full face TBM would not be appropriate for this drive. After careful consideration of the predicted conditions both for ground and tunnelling works, TES, in co-operation with the team from tunnelling contractor J. Murphy & Sons ultimately designed the 9m outside diameter open face shield, with leading edge 'forepoling' boards for initial ground support at the face, that utilised centrally-mounted twin mining booms that could each carry a roadheader drum cutter and/or a bucket excavator. In the event, despite not having been initially designed for this use, ground conditions meant that booms were also utilised with a combination of hydraulic breaker and bucket depending on the ground type encountered.TES received the first enquiry about a possible tunnelling machine from Murphy in November, 2014. The initial brief was that the machine would need to handle foam concrete, solid stone brick and what was believed to be softer ground types along the tunnel bore route. In barely one month an initial design for the excavator-based TBM was presented and Murphy agreed to proceed, provided the unit was ready to be on site no later than July 2015.In just seven months, by July 2015 TES had completed the design, built and completed testing on the shield section of the tunnelling machine. By the end of July, whilst TES was finalising testing of the segment lining erector in the yard, engineers from Murphy were dismantling the front end of the shield alongside TES engineers for transport to site. The complete unit was ultimately dismantled at the TES yard in just two days. At the Farnworth Tunnel site, in association with TES engineers, Murphy rebuilt the whole machine in just five days. The machine commenced tunnelling immediately on completion of the build.Tunnelling worksWhilst the machine was under construction, from March 2015, Murphy had commenced preparation works with the construction of the launch portal for the TBM and filled the old tunnel from end to end completely with 7,500m3 of foam concrete. This was intended to provide support to the old tunnel and surrounding ground as it was excavated. Despite the more than 1,500 test holes drilled to investigate the ground conditions, the drive actually encountered far more sand than was predicted.The excavation removed all of the old tunnel, upsizing the diameter by some 2 to 3m to 9m o.d. The route ran mostly on the line of the old tunnel which included an existing curve. The new tunnel curve however was not as tight as the old one to allow the new route to handle the newer trains. However, the new tunnel route passed very close to the alignment of the Farnworth (running) Tunnel, passing by with as little as 2m clearance at times.As well as removing the old tunnel, the new route also required the invert of the old tunnel to be excavated because the upsizing of the existing tunnel was confined vertically due to limited ground cover over the drive. However, once the new track is completed the track horizon is not expected to be much lower than the old track.At the start of tunnelling works the excavator booms were fitted with roadheader drum cutters which were used to cut through the old tunnel headwall. The high stone strength caused significant vibrations when cutting which meant that the use of the drum cutters had to be limited. So, once sufficient of the headwall was removed it was decided to exchange the drum cutters for hydraulic pick units or peckers to limit the impact of excavation vibrations on the machine structure. Whilst the original TBM design did not take into account the use of peckers, the interchange was made possible with minor modifications so the tunnelling process could proceed. However ground conditions deteriorated into running sand at times which caused delays as Murphy had to inject ground stabilisation resins ahead of the face.This was also a necessity where the tunnel ran beneath the alignment of the A666 road. As the tunnel passed beneath the road, the surface experienced some anticipated subsidence. However plans had been put into place should this occur and the road was resurfaced back to its original level during an overnight operation with minimal, if any, disruption to this busy traffic route.It proved possible to safely excavate while concurrently installing and grouting sections of the tunnel wall as was originally planned. At one other point in the excavation a running sand inrush occurred with some 100t of sand burying the machine face. This caused a further delay as the site had to be open cut using a shaft to re-stabilise the ground over the TBM face. However the remedial works worked very well and despite the ground problems the TBM completed the new 270m tunnel on 30 October 2015.
Metro projects and hydropower schemes continue to drive India’s tunnelling market, and more opportunities are yet to come but challenges remain in the competitive market, Bernadette Ballantyne reports.Until the turn of the new millennium, India's tunnelling market was dominated by hydropower and irrigation tunnels, many of which meant drilling into the challenging geology of the Himalayas. "These are the toughest ground conditions in the world, closely followed by the Andes and then the Alps," says Manoj Verman, president of the Indian National Group of the International Society for Rock Mechanics (ISRM) and an independent consultant on tunnelling and rock mechanics. "The geology is very varied.It is not uncommon to encounter weak zones, shear zones, fault zones and water in the same path," he says noting that the high overburden stresses from the mountain can also cause problems. Combined with the inaccessible nature of some of the locations and the climatic extremes that include snow and flash flooding, working conditions are inhospitable at best and impossible at worst. It is clear to see why projects here are so challenging.Early TBM hurdlesDealing with the hard and changeable Himalayan rock has traditionally been a drill and blast affair, but the use of tunnel boring machine (TBM) appears to be gaining momentum despite an inauspicious start. "In mountainous regions TBMs have been used and the first three projects were a disaster," says Verman. "There is frequently changing geology and if a TBM goes fast it can get stuck and that is a nightmare. If the height of the mountain is very high it stresses too much and if the rock is soft then it squeezes, under the same height of overburden if the rock is strong then it will burst so these two are extreme cases and they both happen under high stress."An early example of a stranded TBM was on the Dul Hasti hydropower project in the Kishtwar district of Jammu and Kashmir, which began preliminary construction in 1985 and became operational in 2007. Shear zones regularly crossed the 9.64km head race tunnel alignment and water seepage was high leading to tunnel roof collapses that eventually buried the TBM, leaving it beyond salvation.Better progressHowever there have been some more positive breakthroughs. In June 2014 contractor and TBM manufacturer Seli announced that it had completed 14.7km of tunnelling on the Kishanganga hydropower project in Kashmir, mainly for construction of the 12km headrace tunnel. Revealing average rates of over 400m per month and a maximum of 816m in a single month, the scheme has been widely recognised as a huge breakthrough for mechanised tunnelling in the Himalayas. "This tunnel was a tremendous success," says Verman pointing to other forthcoming schemes that are planning to use TBMs. Client THDC India has appointed Hindustan Construction Company (HCC) to use a TBM for delivery of a 10m diameter, 12km long head race tunnel for the 444MW Vishnugad-Pilpakoti hydropower scheme in Chamoli in the state of Uttarakhand. The TBM is scheduled for delivery and assembly on site in February 2016.Long awaited success in the mountains combined with a huge demand for TBMs to build a growing number of city wide metro schemes, means that TBM manufacturers are upbeat about the prospects. TBM manufacturer Robbins established its Indian subsidiary in New Delhi in 2005."We started by supplying 10m double shield TBMs to contractors for an irrigation water supply tunnel which is 43km long. It would be the world's longest tunnel without intermediate access once completed," says Kapil Bhati, general manager for Robbins India, noting that the company's 10m-diameter machines are the largest in operation in India today. "The tunnel will take the water from a river and then over to a drought affected areas irrigating 500,000 hectares of land and further providing drinking water. We have completed around 25km as of now with two TBMs. We are still continuing and expected to complete 2.5 years from now," he says.Of course such a huge job has not been without its challenges and although boring of the outlet began in 2007 access to the inlet end was not available until 2011 due to land acquisition issues."After that advancements were pretty good even with geology being more difficult than anticipated. We are still doing around 300m/month average on each side of the tunnel so the production average is good in spite of the hard rock and tough geology," says Bhati.Another water tunnel transferring flows from the same river, is also underway using a third Robbins 10m-diameter machine. The tunnel is half way through with three years to go, says Bhati. A fourth 10m-diameter machine is also building a 12km water transfer tunnel.Metro growthAs these schemes roll on, Robbins has also been busy supplying and supporting machines for metros in India's bustling cities. "Soon after the irrigation tunnels the metro projects started," says Bhati and the company began by supplying machines to Delhi and then Chennai. "Delhi Metro was totally soft ground so we supplied a spoke type of earth pressure balance (EPB) machine. Those machines performed very well and had very good advance rates."The geology of Chennai is mainly soft but there are a couple of areas where there is rock or mixed ground and then we have supplied a mixed face EPB machine for that geology," he says."The result has been a more challenging bore in Chennai with rock at the bottom and soft ground at the top combined with ingress of water. Cutter changes and interventions were challenging but we have still been successful. There are around 200m left to bore."In Jaipur which is currently building the first phase of its metro starting with a 12km east-west connection, 2.8km of which are underground, the company met with soft ground. "The contractor had two old Robbins machines in stock so we refurbished those machines for the contractor and those are being used. The main challenge here is the heritage structures over the top. It is an old city," he says noting that in the areas where the metro transitions from elevated to underground there is just 5m of cover and yet the marginal tolerance is just 1mm.Tip of the icebergThese are just the tip of the metro iceberg. "Right now there are metros being built in New Delhi, Chennai, Calcutta and Bangalore. Elevated and underground both," says Sanjib Bhattacharya, chief of TBM tunnelling at ITD Cementation India, which is comprised of Italian Thai Development Public Company Limited with the Indian branch of the UK's Cementation. In his 22 years with the company Bhattacharya has delivered 50km of traditional tunnelling with NATM and 21km of TBM routes. "We just completed 7km of TBM tunnelling in Delhi. I was the project manager and out of 7km there were four EPB TBMs, two mixed shield and two soil all from Herrenknecht. In Delhi out of 36 machines, some 19 were Herrenknecht," he says. The Delhi metro is now undertaking its third phase of construction which will result in a further 160km of new lines 54km of which are underground. At its peak in mid-2014 there were 26 TBMs working simultaneously. The tunnelling is over 80% complete as Tunnels and Tunnelling goes to press and has not been without its challenges. Bhattacharya says that one particularly tough section was a 1.25km drive that ran beneath Delhi airport's runway for a distance of 400m meaning that the contractor was not able to carry out geotechnical investigations."This was very unpredictable because the geological data was not there. We designed our machine cutterheads and cutting tools on the basis of available geological parameters. It was around rock, we encountered quartzitic rock of around 200-210Mpa. Very, very hard. So in accordance with that we designed our machine to 250MPa. But unfortunately when we entered the airport area where the survey was not possible we encountered 350MPA," says Bhattacharya. As a result the construction costs ballooned from USD 14 to USD 15 per metre to around USD 35 as the hard rock quickly ate up the cutters. "It was a huge cost and meant that we were only getting four or five metres per day."As a result progress on this section was two to three months behind schedule, says Bhattacharya, however he points out that better progress on another drive where they avoided the rock and used the soil EPB machine made back the time.Despite having taken cores every 50m the nature of the airport site prevented investigation in this area and Bhattacharya says that the client accepted this when the contractor made a claim for the additional costs. "In India contracts are very rigid. 400m survey was not possible so we put a claim in and this was (logically) accepted by DMRC as the data couldn't be got in advance."Critical geological dataAs this experience shows, obtaining geological data is critical for any tunnelling project and is an area where Verman says that clients themselves need to put in more effort in the planning stages if they want to see their projects succeed. "The biggest lesson I would offer clients is 'please investigate more'. What is absolutely lacking in the country is proper site investigation or geotechnical investigation before the project," he says pointing to a World Bank study which he led five years ago which reached the same conclusion. "In state of the art projects 3–5% of cost is spent on investigations but in India it is not even 0.5%. People always say they have had geological surprises. They are surprises because they are not investigating. That is the biggest lesson that should be learned.""I fully agree," says Bhati. "There is hardly any sufficient data available before the tendering process commences. We understand regarding areas which have the limitations like Himalayas wherein the cover above the TBM is as high as 1 to 2km. On the other hand, water transfer tunnel projects or metro projects have the accessibility of lands which clients want to cut short by not providing the proper information or doing proper geographical mapping which results in the award of the tender to the contractor as it is," he says."The contractor in turn has to gather that information by himself which takes time therefore delaying the project and losing more time. Better and earlier information on geological details allows the manufacturers to design the machines and give them provisions to equip the machine to encounter all the problems in front."One of the side effects of this is that projects are less attractive to international contractors who are not prepared to take the risks pushed onto the contractors under the design and build arrangements. "For the time being, due to aggressive local competition and actual contract versions comprising unacceptable risks for the contractor, we refrain from tendering for tunnel projects in India," a spokesperson for contractor Strabag says.Yet ironically clients are demanding that international firms participate in main contracts. "Indian clients are putting a condition [in place] that the tunnelling manager must be an expert from outside of India," says Bhattacharya who says that the international financing provided to the metros also pushes for European consultants to be involved."It is true that they have more experience than us but the fact is that we are building experience. I have a team now running four TBMs simultaneously and now I am looking at Mumbai and Kolkata. We have the resources. Only problem is that the Indian companies don't have the technical credentials so they can't pass the technical bids so that is why we are making JVs."However he says that this is changing and that for smaller bores of 1-2km Indian contractors are wining projects without international partners. Another advantage that local firms have is their proximity to clients and their long term market positions which mean that local companies are more willing to accept delayed payments through claims. International firms however see this as too risky.One way of reducing risk, says Bhati is to have the TBM manufacturer support the project through its life, not just at the beginning. "Most of the time delays are because manufacturers are not supporting the project and the contractor is not capable of coping with the difficult geology. On most of the jobs what we are doing we are supporting them on execution on a per metre basis," he says.This strategy has been particularly important to the Bangalore metro for which delays have been widely reported in the local media. Mumbai Metro Line three"On Mumbai Metro there are seven packages and we got package four," says Bhattacharya whose firm ITD Cementation are in joint venture with Continental Engineering Corporation of Taiwan and Tata Projects. Financial bids were opened in October and Tunnels and Tunnelling International understands that the client Mumbai Metro Railway Corporation is currently scrutinising the project budget which is lower than the forecast costs. One of the major issues which will be faced in the execution of metro tunnels in Mumbai city will certainly be the rock strata which will push up the tunnelling costs. The entire 32.5km line is underground."Geological survey suggests 90% rock which will vary from 50 to 150MPa," says Bhati who has first-hand knowledge.Contracts for this line are yet to be signed . Other MetrosMumbai may be the next major project set for award but there are many more on the horizon. "Phase four of Delhi is coming with 90km of tunnelling. Bangalore phase one is about to complete and phase two is coming next year. Chennai phase three coming next year. Kolkata has another two underground packages coming," says Bhattacharya also pointing to forthcoming schemes in Lucknow in Uttar Pradesh, Hyderabad and Puna."The market is very promising perhaps one of the best in the world at this time, says Verman. "Now is the time that the country has to start moving into delivering infrastructure in difficult areas. Many projects are already sanctioned but procedures are such that they are not tumbling out in the way that we expected. However remain very optimistic. I am expecting 2016 to be a crowded year."Data from the Timetric Construction Intelligence Center places the value of work underway with a tunnelling element at USD 31bn however given the scale of projects planned — Verman says there are 3,000km of tunnels in the pipeline, the figure seems likely to rise substantially over the next five years."I was involved in planning a railway through the Himalayas from Rishikesh to Karnaprayag, 125km long alignment of which 105km is in tunnels so that is the kind of project you are looking at and for this kind of distance you have to use TBMs, especially for the longer tunnels," he says.Bhati of Robbins points to four main growth areas for the TBM tunnelling market. "We have hydropower projects in the pipeline which we see being awarded in 2016 and a couple of them will be using heavy provision of TBM. Then the metros like Mumbai which will be awarded in the next few months.Bangalore and Chennai are planning phase two. Seeing the success of Delhi, Bangalore and Chennai everyone sees that it is the best solution possible. For the next 10-15 years one city after the other will keep having metros come up," he says.Water transfer tunnels to divert much needed resources is also a priority, as are road tunnels. "These are the future. People have realised that there is limited space available above ground so we have to go under. There is a 22km underground tunnel in Mumbai which is going to come from the southernmost part of the city through the coast to the airport. It is entirely underground and will be about 12m diameter, and has now been approved.”Learning from the pastExpectations are therefore high for India's growing and maturing tunnelling industry, but challenges remain and Verman urges government to learn from the past in terms of better planning and reducing bureaucracy so that contractors are able to get on and deliver. "There are huge projects coming forward and government should support this industry and nurture it because it is in the government's interest that these projects are built.”
Repairs are finished for giant TBM ‘Bertha’. Patrick Reynolds reports on the two-year-long process.Bertha, better known as Big Bertha, is a 57.5ft (17.53m) diameter tunnel boring machine (TBM) built in 2013 for the Washington State Department of Transportation’s (WSDOT) Alaskan Way Viaduct Replacement tunnel in Seattle, a JV between STP and local firms Frank Coluccio Construction and Mowat Construction, and also HNTB Corp and Intecsa-Inarsa.The machine, built in Japan by Hitachi Zosen Sakai, broke down after an alleged encounter with a steel pipe, damaging several cutting blades, taking two years to fully repair it.By the beginning of 2016, the giant TBM Bertha in Seattle is expected to restart boring on the delayed, central waterfront section of the USD 3.1bn Alaskan Way Viaduct Replacement project, following repairs to the machine.To prepare, Bertha has been undergoing an unusual, if not unique, experience for any TBM, not least the world's largest: she is being buried to commence boring.A 120ft- (36.5m-) deep shaft was constructed to reach the TBM, allowing its vital front section to be brought to the surface for repairs. Following the work, the TBM was reassembled, the cutterhead was turned and other no-load tests were completed. The last task is load testing to relaunch the TBM for its drive below the viaduct.To that end, the shaft has been backfilled with sand and controlled density fill, allowing Bertha to bore once more. Slowly. For a few hundred feet only, at first.Even though the TBM was first launched two-and-a-half years ago, it still has most of its relatively short, 1.7mile- (2.7km-) long tunnel drive yet to finish.The TBM was stopped in a ‘safe haven’, which is a pre-planned, jet-grouted zone designed to allow last checks and adjustments before Bertha bored below the elevated highway again.Fortunately, perhaps, the troubles that brought Bertha to a halt in late 2013 occurred shortly before the machine moved under the seismically-weakened viaduct. Performing a TBM recovery under the viaduct could have been much more difficult. Even outside that zone, the investigation and repairs undertaken presented “a significant challenge”, says Chris Dixon, project manager with Seattle Tunnel Partners (STP), the designbuild JV contractor comprising Dragados and Tutor Perini.Coincidentally, Bertha is preparing to resume boring around the time when, as per the contractor's original schedule target, tunnelling was to have been finished. Bertha is expected to emerge around the beginning of 2017, according to the latest construction schedule issued in November 2015 by STP. The entire Alaskan Way Viaduct Replacement project is to be finished by April 2018.But while the focus shifts from repairing the Hitachi Zosen TBM, and with the tunnelling industry, the coastal city and the state hoping for untroubled progress ahead, the beginnings of legal fights and insurance liability debates over blame have started.The complex arguments over fault, liability and financial consequences are contested between the project owner —Washington State's Department of Transportation (WSDOT), the JV contractor and TBM manufacturer, and various insurers. Lawsuits have been submitted over recent months.Over the two-year standstill, STP and Hitachi Zosen received no payments from the client related to the TBM recovery costs. STP has only received payments for progress achieved on the many other continuing works, such as around the tunnel portals and concreting of the decks within the tunnel bore so far.But, finally, the project looks set to change gear as Bertha prepares to build the rest of the 52ft (15.85m) i.d. tunnel below the waterfront during 2016.Rise of the TBM optionThe aim of the redevelopment project at the waterfront is to improve Seattle's overall transport and economy. Debate over how to do so ran for years, and a host of studies were performed on realizing a fresh infrastructure vision and removing the seismically vulnerable viaduct on state highway SR99.Back in 2008, the leading alternatives did not include the TBM option, especially to construct a large single tunnel, although all possibilities had had reviews.The long-term vision was to create an 'incredible' waterfront for the city — ideally one with minimal traffic on the surface. Putting as much as possible underground was elected to be the way forward, and the deep bore option became a late stage winner in early 2009.The JV contractor proposed building the tunnel with an earth pressure balance TBM, and aimed to have the tunnel open to traffic before the end of 2015. The owner's contract performance deadline was late 2016 for substantial completion of the SR99 tunnel, with performance bonus and penalties either side of the target.STP hired Japan's Hitachi Zosen to manufacture and supply the EPB TBM. Washington state set up an Expert Review Panel (ERP) to look over key assumptions in cost estimates, identify risk during the construction phase, comment on development of funding sources, and consider the project's schedule.Launch, then stopIn late 2011, construction staging commenced in Seattle and manufacturing efforts got underway for the TBM in Japan. The TBM was assembled in dry dock in late 2012, before it was shipped across the Pacific Ocean to Seattle.Many activities in both Seattle and Japan were on the critical path of the project schedule, the ERP cautioned in its February 2013 report. It issued an opinion that the target launch date of June 2013 was not expected to be achieved.However, the TBM was assembled in Seattle over April-July at the south end of the tunnel alignment, and then formally launched at the end of July 2013.Bertha's 2-mile- (3.2km-) long drive was expected to take about 14 months. In its following report of February 2014, the ERP noted that early operation of the TBM had delivered better than expected performance.The tunnelling plan was to set off slowly. The TBM would stop early to perform planned maintenance and checks at key ‘safe havens’ along the first 1,500ft (457m) of the northward drive before then diving below the elevated highway.By early December, and despite the late start in mid-year, the shield had advanced more than 1,000ft (305m), reaching where it was expected to be against the schedule, the ERP reported. The panel also said the shield had advance more quickly than expected by the project team, and pulled back time against the schedule. But then trouble struck. The machine overheated and progress slowed as “unanticipated and increasing resistance was experienced”, WSDOT reported. The TBM was stopped on December 6, 2013.At that point, as per the contract between STP and Hitachi Zosen, STP was about to take ownership of Bertha from the TBM manufacturer. Hand-off was planned to follow after the first, proving and settling, stage of tunnelling, constructing the tunnel up to Ring No. 200, as WSDOT had noted in a statement on December 5, and Dixon confirms.Investigation and recovery planWith Bertha stopped under cover of 60ft (18.2m), the contractor lowered the high water table around the TBM. Drilling wells to a depth of approximately 120ft (36.5m), water pressure was reduced to enable the TBM crew to safely start inspecting the machine’s excavation chamber in early January 2014. Probe holes were also bored ahead to check for potential obstructions.The investigation of the top 15ft (4.6m) of the chamber revealed a piece of 8in (200mm) diameter pipe — a section of steel well casing — in a cutterhead opening, WSDOT reported at the time.In late January, a programme of hyperbaric interventions allowed inspections into more of the excavation chamber. Many of the cutterhead openings were found to be clogged, which was then viewed as the more likely cause on the mining difficulty and not major obstructions — none of which were found inside or in front of the TBM, WSDOT said in February 2014.Then, as a trial, STP restarted the TBM to build a ring. More high temperatures were recorded, like before the December stoppage. Investigating further, STP found damage to the main bearing seal.Laura Newborn, spokeswoman for WSDOT, has expanded on the initial information, explaining to Tunnels & Tunnelling North America that the well-casing was found inside the material blocking a cutterhead opening."The cutterhead was clogged," she says. "The piece of metal was not blocking the opening."She adds that the metal detected in front of the cutterhead turned out to be the nose of the cutterhead. "There was no metal found in front of the machine," she adds.WSDOT said at the time that the steel pipe found in the cutterhead was a well casing, installed in 2002 and used by geologists to study groundwater flows following the 2001 Nisqually earthquake. The owner added that location of the pipe was included in reference materials in the contract. However, according to JV contractor member Tutor Perini's third quarter-2015 results, presented in its 10-Q filing to the Securities and Exchange Commission, STP claims the steel pipe to be a "differing site condition that WSDOT failed to properly disclose." Tutor Perini added that the Disputes Review Board had said the pipe was a differing site condition, but noted that WSDOT has not accepted the finding. WSDOT's spokeswoman told Tunnels & Tunnelling North America the "root cause of the damage to the TBM is still under investigation."Reach and repairSignificant repairs would be needed at the TBM. The ERP said the stoppage to TBM tunnelling would throw out the project schedule by some months. It called on the client and contractor to stay away from debates over blame and financial liability, and keep their focus on investigating and resolving the technical problems.In its February 2014 report, the panel advised that the contractor be given appropriate time to develop a recovery plan. "Returning the TBM to operation should be everyone's primary objective," it added.During the halt in work, the contractor undertook wider inspections and also maintenance work, including replacing damaged cutter tools. But the discovery of damage to the bearing seal system also called for replacement of the main bearing. With such major works required, it was decided that the TBM could not be repaired underground. The shield had to be accessed from the surface and opened up to retrieve the cutterhead and cutter drive unit. STP developed a recovery and improvement plan, which it believed would allow the repaired TBM to resume tunnelling in March 2015.STP's plan was to sink a large diameter access shaft a little ahead of the halted TBM. The 80ft- (24.3m-) wide shaft was built through much of 2014 and readied to receive the TBM.The dormant machine was restarted in February 2015. It broke into the shaft and came to a rest on a concrete cradle, cast on the base of the shaft. Hitachi Zosen hired a heavy lift contractor to extract the front sections of the TBM, and this was done in late March. Mammoet designed a modular lift tower capable of sliding over the 120ft-deep shaft and repair area.Soon after, in its April 2015 report, the ERP said that while reasons for the TBM problems were not yet clear, and also were subject to ongoing legal and commercial debates, the contractor had been constructively using the stoppage period, adding that STP planned "to apply some lessons learned" from the tunnelling work done up until then. The ERP, through its discussion with project parties, said in its April 2015 report that the recovery plan for the TBM "appears to be viable," adding it was reasonably confident the machine could be repaired.The panel added that STP and WSDOT had shared information — "without direction from WSDOT" — on how to improve the TBM's function. "It appears that many of WSDOT's comments have been considered in the redesign and repair plan," ERP said.WSDOT had formed its own Restart Team to monitor the contractor's work and risk and mitigation efforts. "Fully disassembling and assessing the machine was always the key to determining how long the repairs would take," said Dixon, in mid-2015.Revise and rescheduleThe ERP commented the stoppage was "unusually long" due to the scale of investigation and repairs needed, and the area was a congested urban environment with geotechnical challenges. Working around the core recovery challenge, the contractor examined and re-programmed a number of other tasks for the tunnel, such as manufacturing all of the precast segments needed for the entire tunnel and storing them, ready for use. Other re-programmed construction activities, helping to offset some of the effects of the TBM stoppage, have included, says Dixon: • Completing the underground structure of the south operations building; • Constructing the interior cast in-place concrete roadway structure within the completed portion of the bored tunnel; • Advancing north and south cut-and-cover sections enough for their handover to other works packages; and, • Redesigning M&E systems, installing and commissioning them faster in sections instead of keeping with the original plan of doing everything in one go after excavation is completed. By the time of ERP's report in April 2015, the panel had learned the contractor then expected a later restart of the TBM — in August.It also noted, and as STP and WSDOT have continued to say, the rescheduled completion target cannot be determined until after the TBM has been restarted, has bored again but also has been re-checked at the last safe haven.In mid-July, installation of the new main bearing commenced. But the schedule was pushed back further with TBM restart then pencilled for late November.Hitachi Zosen completed the above ground repair works in mid-August, allowing the heavy sections to be placed back down the shaft for reassembly at the open front end of the TBM. Finally, in late November, the cutterhead was rotated and system checks performed in a "no load" test.With those successes, the access shaft finally could be backfilled. The next crucial step for Bertha are the pitstop checks. All being well, the big bore will proceed below Seattle's waterfront over the coming months.* This is a version of an article that first appeared in Tunnels & Tunnelling.
London’s Crossrail project not only now has an official name — it was revealed the the cross-city rail system will be called the Elizabeth line — it is also less than a year away from the start of the first testing phase.It was a year ago that tunnelling was completed — using two tunnel boring machines (TBMs) called Victoria and Elizabeth, continuing with the regal theme.That followed three years of tunnelling that started in May 2012, and now, four years on, the project is approaching 75% complete, says Crossrail project manager Nisrine Chartouny.The first services will start in May 2017 with trains running from Shenfield to Liverpool Street. The tunnels below the capital and ten new stations in central London will open in December 2018 and the line will open fully in December 2019, when it will connect Reading and Heathrow in the west with Shenfield and Abbey Wood in the east.It’s the largest transport project in Europe, and will add around 10% to the capacity of London’s rail network, serving 40 stations — ten of which are new for the project. An estimated 200M passengers will ride the line each year.
Plans for a Helsinki–Tallinn undersea rail tunnel are a step closer to reality after Finnish and Estonian ministers signed a memorandum of understanding (MOU) earlier this year.The MOU binds the two states to further investigate the viability and economic impact of the tunnel’s construction.The 50-mile undersea rail tunnel has been on the table for almost a decade, with multiple studies considering the potential for socio-economic development between the two cities.According to a study financed by the European Union EUBSR Seed Money Facility, published in February 2015, the project is set to be a success.Predicted to treble travel and boost trade, the tunnel, if built, will be one of the longest underwater railway tunnels in the world, serving four million people living within a 200km radius of both capitals. It will also carry about half of future cargo traffic in the area.25,000 daily commuter trips are to be expected in the first ten years after the opening of the railway, which promises improved accessibility and reduced commuting times from the current two-and-a-half hours by ferry to a 30-minute journey. The revenue generated by passenger traffic would amount to €67bn by 2080.Trains will be able to carry 800 passengers each and cargo with a total capacity of 96/TEU, reaching speeds of 250 km/h.Expected to take eight to ten years to be finished, the total cost of the development can vary between €9bn and €13bn and construction work can start anytime between 2025 and 2030. Further plans include the construction of a €3.6bn Rail Baltica high-speed train line to link Finland, the Baltic States and Poland, improving the connection between central and northern Europe.Socio-Economic ImpactA decisive factor on the tunnel’s construction is its ability to boost economic activity in the Nordic region.The region can become one of the significant centres in Northern Europe, as the two cities house more than 2.5M inhabitants and see over 7.5M passengers travel annually by ferry for business or tourism purposes. By 2080, the total number of passengers between the two cities is expected to reach 41M.Although transport via the new tunnel is slated to bring a 1–3% increase to Finland’s GDP within 20 years in operation, that will not be replicated in Estonia, Latvia and Lithuania, which will see only an increase of 0.5% in GDP.Both countries are expected to collect the benefits of the wider consumer market and shared labour market that the tunnel would open to.The European study concludes: "The figures also show that direct and indirect benefits during the construction and operation period to the economy of both countries are remarkable. “The competitiveness of the twin-city area will be strengthened by improved accessibility, new companies and business, better image and a variety in living options.”Risks and ChallengesThe project poses risks in the construction and execution phases as well as economic, political and technological challenges.In its initial phase, the tunnel’s main problems are related to the geology at the proposed exit location in Estonia, as an important source of water supply for the city is located there.Apart from the uncertainty surrounding its funding, the study also warns that "globally, the political risk for the project progress could be a culmination of the crisis between East and West."At a national level, tensions might arise due to the different process and culture surrounding of the decision-making process."The political success of the tunnel project will depend on the wideness of its impact area and how it is combined with the whole transport system of both countries," the study says.These are still early days for any clear decision, but a potential next step for the project would be the foundation of a Finnish-Estonian project organisation followed by a full feasibility study to make it clear when the tunnel is to be expected.According to Hannes Virkus, an adviser at the Estonian ministry of economic affairs, real decisions shouldn't be expected before 2018.* This is a version of an article that first appeared at www.railway-technology.com.
Dubai's Road and Transport Authority (RTA) has awarded a contract worth AED611m ($166m) for the Sheikh Rashid Road-Sheikh Khalifa bin Zayed Road Interchange Project in Dubai, UAE.
The number of projects and the technical capabilities used by the tunnelling market in Europe has strengthened and expanded over the past two decades. Keren Fallwell reports.
When workers broke through the Eurasia Tunnel in August 2015, it marked not only the first time Europe and Asia were connected by a road tunnel, but also represented the crowning achievement for one of the world’s most challenging tunnelling projects.
The Ceneri base tunnel is an integral part of the New Rail Link through the Alps. Sally Spencer reports.
Involving tunnelling through 33km of mountain, the Koralm railway tunnel is set to become the longest entirely within Austrian territory.
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