Maximum safety in the mountain
Maximum safety in the mountain

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

Hard Facts tunnel boring machine s-1319a

  • 5.8 m diameter
  • 105 m length
  • Total weight nearly 1,000 t
  • Gradient: 90.04 % (42°)
  • Dual backloading system with three bracing levels at all times

the stakeholders include