Advanced technologies, mechanisation of equipment with heightened safety features, and timely service and technical support to end-users can help the construction industry deal with construction complexities and pre-empt risks in different geologies and in hostile project sites. P.P. Basistha traces the latest developments and strategies of leading equipment manufacturers in meeting tunnel construction requirements of the contractors.
There is a series of metro, road and rail tunnels, water and sewerage projects lined up for development across the country, with close to 2,750 km of tunnel projects at various construction stages. Each project must contend with its own set of challenges posed by the geological terrain, some of which can be complex and critical in nature.
Since tunnelling is a highly cost intensive job, it requires timely progress, which is monitored by the project developers. For construction companies, the challenge lies in adopting various construction methodologies that achieve faster and better productivity, with very high levels of safety, while keeping operation costs low, and attaining the total lifecycle cost of the equipment.
Hindustan Construction Corporation (HCC), with years of experience in tunnelling, confirms that constructing tunnels across various geological formations in India and its neighbouring countries, pose major challenges, which often are of disproportionate magnitude, uncertainties and risks. According to the company, tunnelling is risky in soils that are relatively younger, and through fragile, weak and jointed rock masses of the Himalayan region, in the Pleistocene area, Deccan Trap, Gondwana, Vindhwan, and other alluvium and pre-Cambrian geologies. The risk is also high in almost all the seismic zones of India.
HCC has built sound construction practices that include detailed geological exploration, project designing, progress monitoring, and feedback filing. According to the construction major, planners, designers, engineers, geologists, and construction contractors have to take into account thickly vegetated, inaccessible terrains, rock formations, small and big shear zones/thrusts, and hydrological conditions at the site. Tunnelling in such places can often pose the threat of face collapse, chimney formation, water-inrush, hot water springs, gas explosion, squeezing and so on. Manufacturers of tunnel boring machines (TBMs), drilling equipment and so on must adapt their machines to the required design and engineering in the project, while meeting the safety standards and progress timelines. The Tunnelling equipment must also be backed by strong technical support by the manufacturers, with regular performance monitoring and trouble shooting.
Quality tunnelling demands reducing over break, arresting damage to the surrounding rock and achieving better blast efficiency. One of the basic requirement for achieving the three things is accuracy in blast hole drilling. Atlas Copco has been making product enhancements in its medium, large and extra-large, face drilling rigs, branded as Boomer.
Debabrata Sain, Marketing Manager-Underground Rock Excavation, Atlas Copco India, says, “The Boomers come with various automation levels, for hole accuracy, accurate depth drilling, measure while drilling, telematics and round log report. Atlas Copco Face Drills are now in fifth generation of Rig Control System (RCS) with more robust components for aggressive environment and demanding situation.” He continues, “Easy access to information is a prerequisite for tunnelling and mining engineers to help them produce a tunnel or a drift that matches the planner’s original design. With Underground Manager intelligent system from Atlas Copco, all of this information is now readily available and is more advanced than its earlier Tunnel Manager.”
He elaborates, “The small and medium rigs are equipped with (upto) two booms, covering cross sections from 6 m2 to 85 m2. We offer rigs with our Direct Control System (DCS) or with computerized Rig Control System (RCS), to which different levels of automation may be added. An extensive range of rock drills is available from 16 kW to 30 kW of impact power.” Atlas Copco offers Boomer L2D, Boomer 282, Boomer S1D, and Boomer XE3C Jumbo drills for the Indian market.
“Our rock bolting rigs used in mining and tunnelling are suitable for roof heights between 1.6-11 meters. Features include a screen handling arm for installation of wire mesh, RCS system for positioning drilling and bolting, and Cop 1132 and Cop 1435 hydraulic rock drills especially designed for bolt hole drilling. Other features are automatic resin injection, automatic cement system, bolt plan navigation and lift and tilt cabin.” Mentions Mr. Sain.
He adds, “In conventional jumbo drills, the operator undertakes the varied functions, based on his own assessment and skill sets. This can lead to inaccuracies due to possible deviation in drilling and other related jobs, causing an improper tunnel profile and not in accordance with the project specifications. This can result in time and cost overruns, and of course, can impact the safety.
With the new intelligent jumbo drills, accurate hole placement, optimal profiling increases that further minimises the overbreaks. Sandvik’s ‘iSURE’ software improves the planning part significantly and offers an overview of the actual drilling process. iSURE gives specific guidance for different stages of drilling and blasting, keeping project costs low, and guaranteeing smooth proceeding of the tunnelling work thus helps in optimizing the drilling and blasting patterns.
Sandvik iSURE and the new generation intelligent DTi series jumbos (like DT921i, DT922i, DT1121i, DT1131i, DT1231i, DT1331i) together form an unbeatably accurate rock excavation system for tunnelling and underground spaces. I-Series jumbos comes from our factory in Finland along with some other conventional drill models suitable for Indian market. Sandvik has a dedicated training facility in Nagpur and a refurbishment centre-cum-workshop that renders aftermarket and maintenance support to key customers.
Surface Stabilization Advancements
Quality shotcrete is gaining prominence in Indian Tunnelling industry, thanks to demand from construction consultants that are following modern tunnelling methods. Shotcrete becomes an inseparable part of all modern tunnelling methods being adopted in Himalayas as the same is integral to the support system. Machines that are technologically advanced and focus on precision machines are gaining prominence over low quality equipment. “Atlas Copco caters to Indian market in two categories- MEYCO ME3 of 20 cum/hr capacity and MEYCO ME5 of 30 cum/hr capacity. Our machines feature all pre-requisites of a shotcrete machine, namely, a shotcrete pump with S-Valve technology controlled through PLC circuit, an accurate PLC assisted dozing circuit for a dozing accuracy of ±2% and the strongest boom in the segment. MEYCO manipulator coupled with MEYCO shotcrete pump ensures minimum shotcrete rebound and desired strength, matching consultant’s requirement of early strength and final strength,” says Mr. Sain. He adds, “Consumers of Atlas Copco MEYCO products are realising the difference between a concrete pump and shotcrete pump.”
Normet India has recently launched its new low pulsation,Spraymec 5100 VCWET Shotcrete machine for the Indian market. The tunnelling equipment conglomerate, which is importing the product from its parent facility in Finland, has delivered six units to different tunnelling projects in the country such as the AMR Irrigation project in Andhra Pradesh and North Frontier Railway. Contractors namely Coastal Engineering and ABC Infrastructure have also acquired Spraymec 5100 VC for their Tunnelling Projects.
He adds, “The accelerator dosing system Nordoser XE in 5100 VC comes with mono style pump and accelerator. The accelerator dosing is synchronised automatically with concrete output, which is controlled electronically by remote control. Nordoser is available with optional low pulsating Normet peristaltic dosing pump Normet LPP-D with additional process information display in cabin. The advanced Normet spraying boom SB 508 D in 5100 VC ensures good reach and reliable operation in small and medium size tunnel profiles. The boom can deliver automatic functions involving vertical and horizontal stabilization, nozzle rotation, and telescopic stroke. For longevity, the upper boom telescope is protected with a heavy-duty, wear-resistant cover. The speed of the movements cab is adjusted from the cabin display, and all the proportional movements are pressure compensated and have proportional output. Added feature of the equipment is the remote-control system for dosing rates, accelerator pump operations, concrete pumping speed, and wall washing cab, all of which can be adjusted from the control box.”
Another new product recently launched from Normet in India is the Spraymec 1430, truck mounted WET shotcrete unit, which was delivered to a recent road tunnelling project in Himachal Pradesh. Normet will soon be offering a dry shotcrete unit from Meyco for slope stabilisation. Dry concrete spraying business from Meyco was acquired by Normet recently, following which, the company will be offering dry shotcrete machines and its own wet shotcrete equipment.
Putzmeister is targeting hydro and road tunnels for its shotcreting solutions, which were used in the recently completed Chenani Nashri link road tunnel project. The products are being marketed and supported through Putzmeister India’s own distribution channels.
Geological complexities & dimensional challenges
There is an emerging demand for compact TBMs for use in constricted areas such as metro projects coming up in urban areas which have diameters shaft restriction for launching and evacuation. This requires design customization as per the project, such that the type and arrangement of the cutting head can meet the requirement of the site. Since the diameter of the TBM must be equal to the diameter of the designed tunnel, including its lining, the machine has to be customised accordingly both for ease of launching and functioning.
Sharing further details, he continues, “Our Latest offering is ‘Crossover’ XRE series of TBMs. This dual mode Crossover machine with centre screw has been successfully used in Australia’s Grosvenor decline tunnel, where it excavated two coal mines access drives 14 times faster than traditional road headers. The same series of machine has been successfully used in hydro power project in Turkey. Robbins can customize the Crossover series as per the requirement of the project and geology and can make XRE (Crossover Rock/EPBM), XRS (Crossover Rock/Slurry ) and XSE (Crossover Slurry/EPBM) which are ideal for mixed ground conditions that might require multiple tunnelling drives .XRE is the most efficient type hybrid machine with characteristics of Single shield hard rock TBM and EPBM for efficient excavations in mixed soils with Rock.”
Mr Bhati points out, “ Since, there is not sufficient data available before the tendering process commences. We understand regarding the areas which has the limitations like Himalayas wherein the cover above the Tunnel is as high as 1000m to 2000m. On the other hand, certain water transfer tunnel project have no accessibility due to the wild life sanctuaries and other constraints and metro projects have less accessibility of lands in urban areas which does not allow the clients to perform proper geographical mapping which results in award of tender to the contractor with limited geological information. Contractor in turn have to gather that information by themselves 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 any problems that may occur while excavation.
Conceding that the TBM are cost intensive and it is vital that the life cycle costs of the equipment should be below the capital investment cost. Mr Bhati Says,” Robbins TBM’s are designed in view to be used in several projects thereby the lifecycle of Robbins product are far more than others as the same machine of any type can be used in multiple projects thereby reducing the burden of capital investment on a single project. Our machines also uses lesser consumables which makes them cost effective to own and operate throughout the duration of the contract.
HCC had deployed a Robbins 10-meter, double shield TBM for constructing a 19.2 km tunnel for Pula Subbaiah Veligonda irrigation channel in Andhra Pradesh. The continuous lining behind the machine has 300-mm thick concrete segments in 6+1 arrangement, making the finished tunnel diameter 9.2 meters. The tunnel path was through sedimentary rock and several faults and folds with some ground water. A probe drill mounted on the machine enabled verification of the geology 30 meters ahead of the TBM. A strict programme of probe drilling along with adequate ground stabilization allowed the TBM to advance through the difficult sections of rock.
HCC had also deployed Robbins TBMs for the smallest and largest diameter tunnels under Brihanmumbai Municipal Corporation.
Mentioning further he says, “Cutterhead designs including tool configurations in our TBMs are generally customized for geological conditions. This is based on anticipation of the project followed by due study of geology, our past experiences. Not to mention, our extensive involvement with the projects at an early stage.”
For the 2.74 km long sewage tunnel with a finished diameter of 2.5 m, HCC used a shield TBM lined with precast concrete segments for boring. Tunnelling challenges included massive and weathered basalt, and the groundwater level along the tunnel alignment. A Herrenknecht hard rock TBM of 3.065-m diameter with integral automatic grout injection system was used. According to HCC, for the first time in India, a shielded hard rock TBM and gasketed linings were used for a project.
TBM Refurbishment, Service & Parts Support
Robbins will soon setup a new refurbishment /Assembly centre near Mumbai in India which will provide service support to the machines through its crew of 200 engineers including 30 experts expatriates whose expertise can make the machines work even in most difficult geologies.
“One way of reducing risk, is to have the TBM manufacturer support the project through its execution, not just at the beginning or limited to the supply of machines. Most of the time delays are because manufacturers due to not fully involved with the project and the contractor has limitations of coping with the difficult geology. On most of the projects where Robbins machines are deployed, we are involved intensively on the project by providing full support with crew /spare parts of TBM, cutters for execution and even operating on per meter basis. The risk of low progress due to adverse geology is absorbed and taken care by Robbins.” Mentions Mr. Bhati.
Herrenknecht India has a skilled team of engineers, technicians and tunnel engineers to which help customers to succeed on challenging projects. Herrenknecht India has a large facility in Chennai which employs a team over 100 experienced technicians from India and abroad for 24/7 site support. “Our Chennai facility also specializes in TBM refurbishment / upgradation to suit new project requirements, cutting tool manufacture as well as centralized supply of spare parts. Herrenknecht Chennai facility exports parts, cutting tools as well as fully assembled TBM’s to various projects in Asia and Europe,” says Mr. Garg.
He informs, “Herrenknecht is the only TBM company having its own workshop for OEM refurbishment of TBMs in India. This becomes increasingly important as OEM refurbishment is a mandatory tender requirement on many projects in the country.”
Good quality spare parts for TBMs, backed by technical support from vendors, through co- engineering with TBM manufacturers, especially for installation and replacements are equally important for the machines to achieve high advanced rates in hostile site conditions.
He adds, “Safety and durability of the hoses and couplers in TBMs will help in delivering the required progression rates. Damage to the hoses can occur from falling rocks, and they must also be flame resistant when working under high temperatures. We have hoses that are 4 to 100 times more abrasion resistance; they contribute towards the total lifecycle costs of the TBMs and drilling and shotcreting equipment. Our Mega Crimp couplings are shorter in length and do not shear off with rock falling on them. The hoses and couplers are manufactured as per Gates’s tested ‘Stamped’ product development strategy, which takes into accountthe required size of the hoses, ambient temperatures, applications, materials to be moved, ends and delivery. Specifications of the hoses and couplings are based on critical simulation tests of actual site conditions conducted at our Lalru and Faridabad manufacturing facilities in Punjab and Haryana. They include impulse tests, ozone tests, volumetric tests, and for oil swell and permeability test, based on which, the additional tough cover is suggested on the hoses.”
He adds, “Installation of hoses through routing in the TBMs and other tunnelling equipment is done by our application engineers in consultation with the OEMs and the end users. The application engineers, while installing the hoses also take into consideration the exact requirements for ease of replacement, when necessary. Currently, we have six application engineers, and we will be further strengthening the service and support arm of our company.”
He adds, “We are well positioned with our wide offerings of compact design loaders of 3-5-6-10-11-14-20-21 tons for use in tunnel construction of 2.5 – 5-meter radius, and articulated dump trucks of 16 to 63 ton payload capacities. The products, are more suitable for underground mining as they are more cost effective. However, with their higher levels of productivity, the loaders and dumpers are also suitable for bigger tunnel infrastructure tunnelling projects for rapid muck evacuation. We will be promoting the products in the tunnel construction sector as a concept, given their advantage in cutting down deployment of large number of machines for muck evacuation. Further, our strategy is to position the loaders and articulated dumpers as a packaged offering by indexing the loading and hauling requirements through carrying out precise calculations.”
To promote its higher capacity products, GHH Fahrzeuge India is eyeing road tunnel projects with larger construction components that include main and escape tunnels, which will make them more suitable in meeting project requirements with higher muck throughput. It is also promoting its HRE tunnel excavatorfor hydropower tunnelling jobs as the single equipment can undertake drilling, bolting, shotcreting and loading.GHH, which has a full-fledged facility in India with a team of 12 technicians, will be adding 50 service engineers this year. It has set up a 2000-sqm training facility in Udaipur to strengthen product service and support to its customers.
Normet products are aimed for safety, productivity and cost optimisation for all customers in UG Construction mainly tunnelling and mining. “We have been carrying large scale advancements in our all our range of equipments accordingly. This is exhibited in our new Utimec LF 100 dumper. Though the typical application of the dumper for muck and blasted materials evacuation is for underground mining due to its high dump bucket capacity @ 12.5 cum, the equipment can find its application for UG mining, as well as for small diameter tunnelling jobs as it features turning radius,” informs Mr. Mukhopadhyay.
Sharing further details, he says, “The new Normet FOPS and ROPS approved safety cabin provides superior visibility and comfortable compartment for the driver and the passenger in LF 100 dumper. Cabin is designed for safe and easy entry and exit. Door openings are wide and hand rails, non slip steps are correctly positioned. New multifunctional display provides information on temperatures, rpm, speed and related information can be recorded for analysis. The powerful liquid cooled turbo charged Mercedez-Benz 170 kw, Tier-3 classified engine option provides clean and efficient operation. Maximum speed in horizontal tunnel is 30 km/hr. The fully reversible 4WD with high traction capability ensures safe and sure movement in difficult ground conditions.”
For delivering of higher productivity, Normet has made air conditioning standard feature in its 5-7-9 cum/hr concrete mixers, capable in working at underground mining tunnels with smaller diameters.
According to Mr. Mukhopadhyaya, “Close to 85 percent availability of the equipments and utilization of their advanced features is ensured by our high levels of product support. This includes, preventive maintenance support based on annual maintenance contracts, operation, maintenance and safety training.”
Normet India provides major refurbishment services that include complete boom refurbishment, and overhauling of transmissions and engines. The company has an active fleet of 250 equipment across various product categories used for varied tunnelling and underground mining projects. In India . “To ensure right and prompt after sales support Normet is setting up a rebuilding and EQ assembling facility in Rajasthan which will be opened in next couple of months.” Says Mr. Mukhopadhyaya. Normet’s business line comprises of underground tunnelling equipments, construction chemicals and rock bolts.
The Way Ahead
There is great scope for tunnelling in many parts of the country, especially in developing urban infrastructure, underground rail and road networks, and transportation in mountainous regions. More refined designing capabilities, analysing instrumentation data, detailed geological exploration, more mechanisation and customisation of equipment as per projects’ requirements, will enhance the construction industry’s ability to foresee uncertainties and thereby pre-empt potential risks, reduce construction time, meet project completion deadlines and generate revenue.