advanced automatic jumbo drills

Equipment with cutting edge technologies is making tunneling smoother at RVNL’s mega railway project and helping contractors overcome geological complexities.

Sandvik’s DT 821 C and DT 922i advanced automatic jumbo drills are piercing through tough Himalayan rocky terrain to give shape to one of India’s mega railway infrastructure projects. P. P. Basistha visits the perilous site to see the machines at work.

The rapid ongoing construction work of 125-km Rishikesh-Karnaprayag Railway line in Uttarakhand, 825 meters above sea level, that commenced in 2019, can be classified as a major railway infrastructure project that Independent India is witnessing. The project, also known as Chardham, will be a key enabler, interconnecting the four major centers of pilgrimage in North India and also facilitate downward travel to the plains. The new route, which will originate from the newly constructed Rishikesh Railway station, will enable movement of hordes of pilgrims from different parts of India and also foreign tourists destined for Gangotri, Yamunotri, Kedarnath and Badrinath and also to ChotaChardham. The project will curtail travel time between Rishikesh to Karnaprayag to about two hours from seven hours at present.

The magnitude of the project, though, can be quantified as lesser than that of the 750-km long Konkan Railway link with 92 tunnels, viaducts and bridges, connecting Maharashtra, Goa and Karnataka, each with its own set of complexities and challenges, given the most arduous terrain, equipment transportation to the site (jumbo drills were used) and their deployment, project execution and so on.

The Rishikesh-Karnaprayag line being constructed in the Himalayas and running parallel to river Ganges, has its own unique challenges, which the project contractors are countering most efficiently. The project requires the construction of 12 stations and 17 tunnels with an escape and main tunnel, ballast-less tracks and 35 bridges.

About 85 percent of the construction has to be carried out inside the tunnels, which poses a separate set of challenges owing to the region’s geological complexities. Though the young nature and hardness of the rock is making tunneling difficult in many places, state-of-the-art mechanization in terms of equipment with cutting edge technologies, is making the drilling smoother.
Prakash Panicker, Joint General Manager - Procurement, Larsen & Toubro
In view of the many challenges in the project, we considered global references on major tunneling projects, alongside L&T’s diligent selection process, while keeping safety and productivity in mind. We decided to select Sandvik, a leading global supplier of drilling technology, as our partner for rock drilling technology in the project. We procured 6 units last year for RVNL Package 2 which are giving exceptional results contributing to the progress of the project. We have again shown confidence in Sandvik by adding 2 units of Sandvik’s most modern and fully automatic DT922i, and 4 units of their semi-automatic DT821C to our fleet which will be deployed at Package 4 sites.

Prakash Panicker, Joint General Manager - Procurement, Larsen & Toubro

The Rishikesh-Karnaprayag rail line project has been divided into 10 packages. Contractors involved in the project are namely L&T, Navayuga, Rithwik, HCC-DBL, Megha and MAX-HES JV. L&T has been awarded package 2 of the project. Its scope of work between Shivpuri to Byasi involves constructing a major rail girder bridge at Shivpuri, constructing a station at Byasi which will lead to the main and escape tunnels, covering different gradients. Both the main and escape tunnels are of 14x2 and a total distance of 28 kms.

advanced automatic jumbo drills

The company is utilizing Sandvik’s DT821C and the newly advanced DT 922i jumbo (also the star attraction). These equipment are penetrating the rocks with face drilling, bolt hole drilling and long hole drilling with the required power for constructing the main railway tunnel and the parallel escape tunnel.

L&T is convinced that automation and digitalization in Sandvik’s drilling machines has helped them in assessing the geology and capturing data for advanced analysis in order to plan and execute the drilling pattern - all of which has enabled L&T’s team to derive a lesser cost per meter while drilling.

Observations of Prabhu Kumar, Project Manager, RVNL- Package 2, Larsen & Toubro, on the Project Challenges & Requirement for Highly Advanced Drilling Equipment Technology
RVNL’s Rishikesh to Karnaprayag is a project of national interest and one of the most prestigious tunneling projects in our portfolio. We will have to deal with unique geographical challenges through the young Himalayan rock class. The heterogeneous characteristic of the rock includes different types of rock class with layers of purple sandstone and quartz arenite, with different levels of hardness and abrasiveness.

Besides this, we have a tighter completion schedule of the tunnels by 2024. The operation of the rail link is scheduled by 2025 as set by RVNL. All this has made it imperative for us to deploy state-of-art construction plants and machinery to achieve reliable, productive, and safe execution of the project.

While the DT922i will be mainly deployed for the Main Tunnel (MT) excavation, the DT821C will be used for the Escape Tunnel (ET) excavation program; nevertheless, both the drill jumbos are flexible enough to be deployed either way, in case the situation demands.

Both the drill jumbos are reinforced through Sandvik’s unique drill plan office software – iSURE® (Intelligent Sandvik Underground Rock Excavation). The iSURE program is allowing our geologist and tunnel engineers to make project tunnel line, make an accurate navigation plan (using total station, laser or bit navigation methods), face drilling plan, drilling boom sequences, blasting pattern, charging results, pull-out analysis and so on.

With iSURE® program, we have succeeded in eliminating the manual navigation and hole painting / marking on face of the tunnel, as every detail comes in front of the operator on the touch screen computer. In the conventional (hydraulic) jumbo drills that we have seen, the operator undertakes various functions based on his own assessment to select the hole to be drilled at the desired depth, which is sometimes not accurate enough as needed, besides which, any human error can lead to inaccuracies due to possible deviation in drilling, which can cause an improper tunnel profile, poor advance, and/or under/over-break excavation. This can result in time and cost overruns and impact safety as well.
Prabhu Kumar
In my opinion, the advanced features in DTi & iSURE will reduce the over- and under- break by 7- 9% as compared to traditional jumbos; this is really a big saving for L&T when you consider the overall project span.

Prabhu Kumar

Using the DTi & TCAD+ Jumbos and iSURE software increases the accuracy of hole placement and depth, which minimizes the over-breaks. In my opinion, it will be reduced to 7- 9% compared to traditional manual jumbos, and this is really a big saving for L&T. It will enable us to make huge savings in re-filling and scaling materials, besides saving on time and resources. Most significantly, it has allowed us to optimize the drilling and blasting patterns.

Many of the main challenges in tunneling is the probable prevalence of under and over breaks, less advance per round, not optimum rock fragmentation after blast, which can occur due to inaccurate planning of drilled holes and blasting quality. This can distort the tunneling cycle and lead to distortion on the tunnel profile. However, with the iSURE package (that assists in geological interpretation and rock analysis during drilling), we have been able to make significant progress in drilling with high accuracy, much in accordance with the predesigned drill plan, and with minimal operator intervention.

Highly Advanced Drilling Equipment Technology

We have opted for Sandvik GeoSURE® package that is in-built in iSURE program. GeoSURE® is a rock mass analysis and visualization system for Sandvik DT922i jumbo. It’s real-time onboard analysis enables accurate results with high precision data that allows us to predict type of rock ahead on face and also to determine type of rock support needed in a particular tunnel peg. GeoSURE® enables us to save time and costs by fulfilling the most advanced reporting requirements while enabling new ways to optimize the tunneling process. It’s a very impressive and helpful tool for us.

This has been my first hand experience with such a detailed and proven Drill & Blast office program for tunneling jumbos. ISURE® gives us constant data and the latest reports to help review and improve our overall operation efficiency. Our team has now become very familiar with iSURE for the day to day drilling application.

Observations of Sankar Kumar, Plant & Machinery In-charge, RVNL Package-2, Larsen & Toubro, on the Performance of Sandvik’s Advanced Machines in the project.
It is necessary to have equipment with the latest safety and automated features as they enable better utilization and higher productivity for such time-bound projects. For example, in conventional jumbos, additional manpower is required for loading and unloading or drilling rod while doing long holes, which is definitely not safe and takes a lot of time to complete.

However, in the DT 922i there is an in-built Tunnel Rod Handling (TRH) system (that carries 4 additional rods in the carousal) to allow the operator to execute long holes drilling from the cabin itself. This facility certainly adds to safety and saves a lot of time while coupling and uncoupling of the rods mechanically from the cabin.

Also, these conventional jumbos do not have any provision to maintain records and generate reports, which are important tools to review and to optimize the operation. These gaps in performance have been largely filled by DT922i and DT821C units, as we can review the utilization of the machine, drilling and non-drilling activity times and so on. Both the machines have not only helped us in faster drilling but also enhanced the level of safety.

We welcome Sandvik’s proposal to select their latest rock drills (drifter) Model: RD525 – 25KW impact power on both the jumbo models: DT821C as well as DT922i. With this, we have great flexibility with interchangeability of the rock drills and its parts among our fleet of Sandvik jumbos during service and schedule maintenance. The official service intervals of RD525 are scheduled at 750 percussion hours (instead of the traditional 500 hours interval).
Sankar Kumar
I’m very impressed by the drilling performance of Sandvik’s RD525 - 25KW rock drill as it drills approx 30% faster than other rock drills in market. Moreover, Sandvik’s training simulator and proactive aftermarket approach are the best that we have experienced so far.

Sankar Kumar

I am very impressed with the performance of the RD525 rock drills due to their higher penetration rate (as >3.5m/min on face drilling), which helped us realize approx 30% less face drilling time per round, as compared to the conventional lesser-powered rock drills.

DT 821
In the beginning, I thought there would be scarcity of skilled operators for these computerized jumbos in India; however, Sandvik is providing on-site Training Simulator (it has exactly the same controls of DTi jumbo), which includes syllabus, examination and certification on completion of the operator training. We have deputed our operators to undertake the simulator training prior to the arrival of the real rig at site. I have found excellent results on operator skill and knowledge on operating the machines on completion of the training program.

In fact, since the inception of the project, we have received all the application engineering support from Sandvik, along with their service engineers and timely parts supply (most essentially, the drilling tools), so that we have been able to derive optimum utilization of the machines. This has given us the confidence for timely handing over of the project to RVNL.

We are using Sandvik’s Alpha series Drifter Rods and the recently launched Speedy Button Bit in our project. Sandvik rock tools application expert visits us from time to time and shares the best practices to enhance the performance and service life of the rock tools. We are also planning to induct Sandvik’s button bit grinding station to improve the button bit life even further.