The first Sandvik DT922i, a computer controlled fully automatic tunneling jumbo, has been introduced by Sandvik Mining and Rock Technology in India with a vision to achieve high levels of safety, productivity and precise tunneling.
Tunneling for infrastructure projects is becoming more and more mechanized by use of TBMs and other methods. However, the Drill and Blast method is more flexible as it is easier to adopt to varying profile requirements as compared to a TBM, which gives a circular cross section, especially for railway tunnels, resulting in a lot of over excavation in relation to the actual cross section needed.
The first Sandvik DT922i machine in India was supplied to Rail Vikas Nigam Limited (RVNL) appointed contractor, APCO Infratech. The advanced automated tunneling jumbo has been used to drill the first ADIT for access to the main tunnel, which is part of the 125-km Rishikesh–Karanprayag Railway line, for which the work began in 2019 and the entire line is expected to be operational by 2024/25.
The Rishikesh to Karanprayag Railway, once completed, will provide a broad-gauge railway, linking Rishikesh with Karnaprayag. It is Indian Railways’ chosen route for the Char Dham Railway to connect to the Chota Char Dham, and is one of the major initiatives of the Indian government to improve transport and communication in the area. The 125-km route starts at the newly built Rishikesh railway station located 380 meters above sea level, and terminates at Karanprayag, 825 meters above sea level. The project will reduce the travel time between Rishikesh and Karanprayag from the current seven hours (approx) to about two hours.
Challenges: geological conditions, rock hardness & stricter deadlines
The railway line is being constructed in the Himalayas, running parallel to the river Ganges. The main tunnel will have a parallel escape tunnel and ballast-less track that will run inside. The project has a total of 10 packages, out of which 8 have already been awarded to various contractors, including L&T, Navayuga, Rithwik, HCC-DBL and Megha.
The actual rock encountered during tunneling was mainly purple sandstone / quartz arsenite. In addition to the rocky terrain, operator safety was a prime consideration keeping in mind the tough geographical conditions. The stricter completion deadlines of the project required the use of equipment with a high level of automated features for better utilization for greater productivity.
Added Jain, “In a conventional hydraulic underground drill rig, the tunnel profile is based on the judgement of the operator on where to drill, and at what angle or depth. In traditional solutions, the tunnel profile is not always accurate due to human error, and drilling holes may not be accurately placed or at the desired angle. This often results in over breaks or under breaks on the tunnel, which is expensive and requires the driller to fix the arising issues as well as provide further expensive roof support. These problems slow down the entire construction work, and the project gets delayed, often with cost overruns.”
The introduction of the fully automated Sandvik DT922i completely changed the rules of the game. The entire drilling cycle is automated, hence, operator drilling judgment is eliminated. This means more accuracy and precision in drilling.
Sandvik DT922i fully automatic twin boom jumbo: Intelligent yet flexible and adaptable
The fully automatic Sandvik DT922i machine comes equipped with Sandvik’s intelligent iSURE® and iSURE® GEO patented software for underground rock excavation. It is making the tunneling excavation safer and more productive. As with all Sandvik ‘i’ Series rigs, the DT922i effectively provides automated multipurpose face drilling with the capability to drill one complete round accurately, with a high level of repeatability according to a pre-designed drill plan, and with minimal intervention by the operator. This is because the iSURE® system for data collection analysis and process control improves the work cycle and processes. It assists in geological interpretation, thereby providing considerable savings in the drill and blast operation. It also generates critical reports on drilling operation, efficiency, and utilization of the DT922i rig, and provides drilling parameters in order to assess blasting vibration and pull-out.
Rock analysis & project management software
The application of DT922i and its iSURE® MWD (measure while drilling) system has ensured that the drill and blast process has been optimized since the template-based drill plan has considered rock blast-ability, tunnel profile, target and explosives used. This has resulted in controlled blasting with a good pull-out, restricted fracture zone, and greater rock strength around the ~1 km tunnel. Furthermore, the blasting round’s length and detonation are tuned to the allowed vibration level and geology. iSURE® helps achieve the best possible result from the blast as it provides a set of templates for editing and feedback functions, with blast patterns being easily edited to match the design parameters.
The iSURE® GEO in DT922i is a rig-integrated, high precision, online rock mass analysis and visualization system designed for optimization of tunneling processes, and is fully integrated with the iSURE® tunneling project management software. It has proved to be highly effective in improving the overall Devprayag and Lachmoli tunneling process by providing geological information on the Himalayan rock, onboard analysis of the rock mass, advanced reporting, and helped in the assessment of rock reinforcement or injection requirements, in the charging and blasting control, and in geological mapping.
In effect, the iSURE® GEO system acta as an analyzer as all information is provided on the drilling rig itself through the software, and effective sensors have helped users to provide accurate and repeatable results.
Sandvik DT922i: Designed to be tough
The rugged Sandvik DT922i has been designed to operate in the toughest of working conditions in India’s diverse terrains and regions. Its unique design comprising of a small number of hydraulic hoses, minimizes oil spillage (a key environmental concern of the Indian Railways), which cuts down the frequency of maintenance and downtime of the machine.
Since the jumbo is required to work in some of the harshest conditions and continuously for hours, due care has been taken to ensure the safety and comfort of the operator. The DT922i has a sound-proof iCAB operator cabin, which conforms to ROPS (roll over protection system) and FOPS (fall over protection system) certifications, while state-of-the-art ergonomics with joystick controls ensure comfortable and safe working environment. To improve drill and blast performance, Sandvik Alpha rods and bits ensure higher rate of penetration and a longer life (an estimated increase of ~20%).
Training and hiring operators with the right skill set
Sandvik believes that a jumbo or any machine is only as good as the people who use it. To get the best efficiency and productivity through sourcing workers with the right skill set, in February 2020, the company along with RVNL officials, inaugurated a drill simulator training facility at the RVNL campus in Rishikesh, where it trains operators on its simulator - Sandvik Digital Driller™ as per the specifications of the rig. Moreover, Sandvik is also providing round-the-clock support, regular servicing and maintenance, genuine parts, and rock tools from its local warehouse to make sure that its customers get hassle-free operation all the time.