Sandvik Construction supports Afcon’s in Jammu and Kashmir
Mumbai based Afcons Infrastructure Limited is one of India's leading infrastructure construction companies. Sandvik's partnership with Afcons dates back to 2006 when two DT820s were supplied for railway projects. In early 2014, Afcons received two further tunneling contracts in Jammu and Kashmir worth over $250 million. This resulted in further orders for new Sandvik DT820 tunneling drill jumbos which have made light work of the tough operating conditions.
Afcons Infrastructure Ltd, which stands for special technical solutions, has played a major role in a series of tunneling projects across India. Recent Afcons projects include the Calcutta Metro, which involved a particularly challenging tunnel under the river; a highway tunnel in Rohtang, which was constructed in extreme conditions, as well as the Chennai Metro project which used some of India's most advanced tunneling methods. Following these successes, in early 2014 Afcons received two further tunneling project contracts in Jammu and Kashmir.
These projects are considered to be some of India's most significant road-building initiatives (National Highway 1, NH-1) and involve redeveloping the route from Jammu to Udhampur, and are worth in the region of $250 million US Dollar. Commissioned by the National Highway Authority of India the project is run along BOT – Build, Operate and Transfer – lines. When complete the road will be extended from two to four lanes, and will result in travelling time being reduced to approximately six hours from the present ten hours.
In the course of redeveloping the highway, around 150 bridges and numerous tunnels had to be built in the extremely inaccessible terrain of the Himalayas. Afcon's thus found itself facing quite special challenges in executing the project. First and foremost, the climatic conditions are extreme, varying from very high temperatures in the summer to pronouncedly low in the winter, with snowfalls and monsoon rains. In addition, the construction sites are located in a remote area with the route leading through a wildlife sanctuary located at Nandini. As a result, drill and blast was precluded from the very outset and conventional driving was plumped for.
Over a length of 65km of the NH1 Highway between Jammu and Udhampur, Afcons was engaged in producing four twin tube tunnels with a total length of 1.5km each. The project that began in 2011 was completed in September 2014. At one point Afcons was three months ahead of what is already an ambitious schedule. "With 75% already finished, Afcons will mark one of the best milestones in the career of construction", Biplob Chakraborty, Deputy General Manager Construction Plant and Equipment of Afcons proudly stated at the time.
This milestone was achieved by the choice of the right partner for the fleet of equipment. Chakraborty describes the decision: "We needed a special machine for excavation and drilling. We had to find a company which is well known and established in the market. In tunneling machinery, Sandvik is a preferred choice as their machines can work uninterrupted and supply hassle-free productivity. This is my experience". But for the experienced management of Afcons there is more than quality and a good reputation involved: "It is not only the machine that is important. After sales, good service and maintenance are also a very big point for us when we decide for a supplier", describes Mihir Mishra, Deputy General Manager (C.P.E.) of Afcons Headquarters in Mumbai who is also responsible for equipment acquisition.
A major complexity on the project was the geology which is typical for the young Himalayan chain. Poor quality, broken rock with dolomitic limestone, and firestone lentils with high silicate content are mainly to be found. Rock class III to V, with strength of 60 to 100MPa and volume weight of 2,7t/m³, is prevalent. The RMR (rock mass rating) index amounts from 40 to 60. The tricky ground conditions in particular made it necessary to have a reliable partner for securing the rock. "The rock can collapse at any moment so that we must support the face quickly. We have a very reliable partner here with Sandvik", Mishra continues.
Sandvik has been a partner of Afcons for many years dating back to 2006 when two Sandvik DT820s were deployed on railway projects in Jammu and Kashmir. As a result, it was easy for Afcons and Sandvik to jointly discuss the necessary equipment, special solutions and estimated costs during the offer phase of the project. Solutions were found for technical support and service, including the prompt delivery of spare parts and Sandvik training for operators. Additionally the exceptional flexibility of the Sandvik DT820 tunneling jumbos was considered a major advantage for the overall project. For example, if the face is very small, the two booms can be operated within the available limited space, just as is the case with a large face area. These features and aftermarket support resulted in a further order of two new Sandvik DT820 tunneling drill jumbos.
Tunnel Design and Excavation
The design of the four twin tube tunnels (148, 250, 469 and 550m long), with a total length of approximately 1.5 kilometers each, is straightforward. The tunnels have a gap of 25 to 30m between them, and in the case of emergency, every tunnel can be used for evacuation. The tunnels were constructed by conventional mechanical cutting methods (NATM). The portals at the accesses to each tunnel are supported by steel arches over a length of 10m and are lined by placing a layer of wet shotcrete with steel fiber meshing.
Due to the operating requirements necessary due to the sensitive nature of the local environment (Nandini Nature Sanctuary) and taking consideration of the local inhabitants, a mandate to use conventional mechanical cutting methods (non-blasting operation) in tunnel excavation was imposed. This meant that at the face of the tunnel, the jumbo is used for drilling profile holes. The profile holes act as guiding lines for the mechanical cutting excavation; the 3m deep drill holes are created in order to be able to excavate the correct cross-section (tunnel profile). The actual excavation was done by different methods of mechanical cutting: roadheaders, drum cutter and vibro-ripper attachments. The resulting residue was loaded by excavator on large dumpers and then transported out of the tunnel.
Sandvik jumbos were also extensively used for rock stabilization and roof bolting. For rock bolting, hole diameters between 54 to 64mm with a depth of 4 to 10m, were used. When very poor rock (Class IV and V) was encountered the Sandvik jumbos were also used for pipe roofing – or umbrella drilling – applications. A pipe roofing kit was retrofitted to both jumbos for this purpose, and steel pipes with 114mm diameter and depths of 12 to 15m were inserted by the jumbos. Along with the DT820s, Afcons also used Sandvik rock tools for profile drilling, roof bolting and pipe roofing applications. The Sandvik drill jumbos and rock tools proved to be an excellent match for these challenging drilling conditions.
The Sandvik DT820 itself is a hydro-electric underground drill rig equipped with two booms and a utility boom as well as different optional instrumentation levels. Its coverage area ranges from 12 to 110m², with hole diameter ranging from 43 to 63mm and the length from 3,440 to 6,180mm. The Afcons jumbos were equipped with a TFX-10/14ft. telescopic feed and a pipe roofing kit. With this equipment, it was possible to drill a tunnel of 8.42m in height and 14.21m in width. Work progressed well with an average advance rate of 14.5m per day which meant that excavation work was finished in June 2014.
Service and Maintenance
Service and maintenance play major roles in any tunneling project, and this project was no different. Sandvik service engineers Rohit Singh Pawar and Virender Kumar working together with Afcons Engineer Murali Patel Virender Singh, who looks after the company's tunneling sites. Their tasks ranged from training the operators to giving assistance to the Afcons mechanics. The Sandvik service team also took orders for spare parts and repaired the machines if and when needed. They also planned the deployment times for the machines and worked out the service plans adapted to these deployment times. In this way, the jumbos were available for use at all times. Spare parts and rock tools were dispatched to site from Sandvik distribution centers in India.
The right choice for the project
"The machinery part of a project influences its success and due to this, it is very important to have a supplier like Sandvik", states Biplob Chakraborty, Deputy General Manager (C.P.E.), Afcons. "For this reason, there was no question in choosing Sandvik as partner". Afcons' success proved to be a win-win for both parties with more orders being imminent for both the Construction Company and Sandvik Construction.
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