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Maximum safety in the mountain

Marti will start tunnel driving on the pressure shaft for the new Limberg III pumped-storage plant in Salzburgerland, Austria, in the spring. This inclined shaft will be drilled at a gradient of 90.04 %. The safety and performance requirements of the tunnel boring machine to be used are consequently high. The factory acceptance test of this advanced gripper TBM will now take place at the beginning of February at the manufacturer Herrenknecht in Germany.

The TBM is now fully assembled and ready for factory acceptance testing in a workshop of Herrenknecht AG in Schwanau, Germany. In close cooperation with Marti, Herrenknecht planned, developed, and designed the gripper TBM specifically for the gradient to be tackled.

Two-Fold Backloading System at All Times

To prevent the TBM from sliding down in an uncontrolled manner at the gradient of 90.04 %, which corresponds to 42°, it must be braced. Three bracing levels ensure that the machine is clamped in two planes at all times during operation. The gripper bracing directly behind the drill head is the first bracing level of the TBM. The gripper plates generate hydraulic pressure on the tunnel wall while the tunnel is advanced using the jacking cylinders. The trailer is followed by the second bracing level with the backloading system 1 and the third bracing level with the backloading system 2. While the first backloading system is rigidly connected to the trailer, the second is hydraulically automated and travels with the driving equipment. This ensures that the trailer moves at the same speed as the TBM. If one of the three bracing levels must be moved, the other two secure the machine at two locations at all times. The toggle lever system ensures that the backloading systems are automatically locked in place using hydraulic and mechanical methods. If the machine slips back in an uncontrolled manner, the bracing force automatically increases with this system, ensuring maximum safety. Each of the three bracing levels can independently support the entire weight of the TBM.

Safety in the Drill Head

The design of the drill head also complies with the highest safety standards. The backloading system makes it possible to replace the roller bits in the protected area from inside the drill head. This means that the employees no longer have to work in front of the working face. As a result, they are no longer exposed to the geology and possible falling rocks. Using the appropriate tools, this ensures that the rollers can be changed as ergonomically and safely as possible.

Preparation at the Construction Site

Work at the construction site in Kaprun in Salzburgerland, Austria, is now in full swing. A team from Marti Tunnel is focused on building the correspondingly steep ramp for the TBM. The slope and weight of the start ramp, which runs at the same time, also make this work highly demanding from a safety point of view. Each individual ramp support weighs 10 t. Once the ramp is ready and the TBM has been transported to the construction site in individual parts, the on-site assembly starts. The machine is assembled piece by piece and pushed up the ramp girders on hydraulic cylinders in the cavern until it is complete. The machine and shafting equipment is designed to prevent collisions between the trailers and the machine when tilted. Driving operations are scheduled to start as early as May 2022.

“It doesn’t get much steeper than this! There were a huge number of interfaces to take into consideration, both in the planning stage and on the construction site. Safety requirements were our top priority.”

Steffen Wiedemer,
Project Manager Herrenknecht