Tunnel specific equipment such as lifting and steel arch installation Equipment is built on a carrier especially designed for the rigors and demands of a modern tunnel environment.

Tunneling?s evolution through the 20th century involved a dramatic increase in mechanisation as available technologies developed. However, in many cases, the specialised needs of tunneling were not specifically addressed and instead innovative and adaptable contractors utilised available equipment (for example, construction, industrial, or mining focused) either ?as is? or modified on-site to their purposes.

One early trend for tunneling in the 21st Century has been the marked increase in usage of equipment specifically designed for modern applications (referencing here non-TBM tunnels). This has ranged from the more traditional disciplines such as explosives charging and elevated staging to include scaling, concrete spraying, arch installation and utility functions. The tunnel specific equipment offers significant benefits to their operators in terms of safety, speed and efficiency of operations and, in some cases, multi-tasking. The construction of underground infrastructure is on a significant rise and suppliers such as Normet are assertively developing technologies to keep pace. This paper discusses the above trend with a focus to lifting and explosives charging.

General features

Tunnel specific equipment is built on a carrier especially designed for the rigors and demands of a modern tunnel environment. The equipment is designed to be used continuously in harsh, wet and sometimes corrosive underground conditions where fresh air is limited and with a paramount view to the highest requirements for safety, not just for the operator specifically but also those that might be present in and around the operating equipment.

Typical features of tunnel specific equipment include:

• FOPS (Falling Object Protective Structure) approved driver?s safety cabin and operator?s safety roof in man lifting devices
• ROPS (Roll Over Protective Structure) approved driver?s cabin in all earthmoving and transportation units oil immersed disc brakes
• Working and warning lights, especially designed for unlit tunnel driving
• ?reverse driving? view camera
• State-of-the-art, electronically controlled diesel engines according to Tier 3 classification
• Catalytic converter and exhaust particle filter
• Fire-extinguishing system
• The option of electric over hydraulic power for equipment working statically for longer durations (for example, explosives charging or lifting equipment at the tunnel face)
• Robust and stable carrier
• Hydraulic and electric components designed for use in harsh environments
• For utility function vehicles, modular carrier construction allowing multi-purpose utilisation of the same carrier

Man lifting equipment

Man lifting applications are required in several phases of underground work such as explosives charging, manual scaling, installation of ground reinforcement and support, as well as in all kinds of utility works typically carried out behind the tunnel face. Functions like geological mapping and the monitoring of ground control systems need work platform service as well. Specific tunnel dimensions and work methods set the minimum requirements for the reach and lifting capacities of the equipment. Tunnel specific equipment provides more efficient and versatile solutions for underground works when compared to conventional lifting equipment like scissors lifts and telescopic handlers, and provides greater tramming efficiency versus simple boom lifters.

Tunnel specific boom and basket concepts vs conventional lifting devices

Tunnel specific man lifting devices typically use one or two multi-directional operating booms with a total slew angle up to 60 degrees, providing a true three dimensional working zone (longitudinal, vertical and horizontal) in the tunnel. With a multi-directional operating boom and basket system, the operator can reach the full tunnel profile without the need to reposition the carrier in a horizontal direction. Conventional telescopic handlers usually provide the boom movements only in 2-directions (longitudinal and vertical) and scissors lifts usually come only with vertical and minimal lateral movement. Movements across the face with a conventional lifting device can be provided only by moving the carrier sidewise in the tunnel which brings unnecessary delays to the work process.

Tunnel specific booms are structured to be more robust and are typically welded from heavier steel than conventional booms. Lifters are designed to stay stable and maintain operator safety even in extreme situations such as falling rock hitting the boom structure. Conventional light lifting devices often cannot remain stable in such situations and this is a noticeable safety issue to be evaluated when selecting lifting devices for tunnel works.

One advantageous feature of a tunnel specific lifting device is that it can be operated from the basket. This is a big benefit compared to conventional telescopic handlers that usually need an additional operator sitting down in the driver?s cabin or adjacent to the machine. To contrast, ?telehandlers? are designed primarily for the rapid movement of palletised cargo or other loads on surface applications by using pallet forks and adapting them to man lifting works is often done with a non-ideal lift table attachment that replaces the forks.

Drilling jumbos may have an additional boom and basket which is designed for light man lifting works while the machine is stationary at the face. In this case, the basket may be used for the manual handling of rods when doing long hole drilling such as for grout holes or it can also be used for small scale scaling and or support works at the face in conjunction with the drilling procedure. However, because the drill jumbo often has multiple faces to operate and a high investment cost, it is not beneficial to use the drill jumbo for other lifting applications. All other works at tunnel face may be accomplished faster by using tunnel specific two boom lifters

According to the new European Machinery Directive, which came into effect on Jan 1st 2010, a safety roof is compulsory in all man lifting devices in underground works if there is a risk for falling objects. Tunnel specific lifting devices come with a FOPS approved operator?s safety roof as standard. A safety roof can be set back or removed totally when works are done under a supported roof such as in final tunnel lining structures.

Twin boom lifter concept

A twin boom concept such as the Himec 9905 BT (Fig. 1) with a 500 kg total lifting capacity per basket is a versatile solution for typical medium load lifting works at the tunnel face. The reach from one set-up to 11.7 m height and to 16 m total lateral width covers most tunnel profiles used in civil construction today. Two booms allow works to be carried out by two independent operators at the face. This can cut down cycle time remarkably compared to single boom operation from the basket of a drill rig or a conventional telescopic handler. Time savings in the installation of light steel arches, wire mesh, anchors and drainage systems vary between 20-40 per cent. In face charging works, time economies of up to 50 per cent can be attained compared to one man operation from one basket.

High reach boom and large basket lifter concept

A high reach boom concept such as the Himec 9915 B or Charmec 9910 B REX uses a heavy duty boom and work platform capable of lifting loads of 1,500 kg and 1,000 kg respectively. The large basket can easily lift up a multiple worker crew with necessary tools and materials. A maximum 9.0 m platform height allows a working reach up to 11 m. The working area of the basic 9915 B platform is 2.4 x 2.4 m but the hydraulically extendable REX-platform provides a variable horizontal plane up to 2.40 x 4.70 m.

The 2.4m boom extension enables maintenance of the platform a safe distance from the tunnel face during its entire vertical travel. Platform rotation permits lining up parallel to the face when slewing the boom through a 60? slewing range.

The large working area of the platform allows simultaneous work by several operators, thus making the product favorable for the explosives charging of large tunnel faces by a charging team. High lifting load and large coverage have made it a popular configuration also for utility works like ventilation ducting, electrical works and piping for water and compressed air conveyance. The stable construction also permits use for sampling, measuring, surveying, roof bolting and manual sprayed concrete applications.

Steel arch installation equipment

Heavy steel arch installation is an inseparable part of many conventional tunnelling operations in softer ground conditions. Steel arches are typically curved I-profiles made from variable thickness steel. In smaller tunnels, the steel support may be formed by using only one steel arch which is curved in relation to the tunnel profile. In larger tunnels, steel arch support is formed by building the final arch over the profile from 2-5 separate curved I-profiles. The weight of a steel arch piece to be lifted varies typically from 250-1,000 kg.

Because of extremely heavy loads, no compromise with work safety during the lifting work may be tolerated. Only purpose-built arch lifting and installation equipment should be used for heavy steel support works as any other construction machine cannot provide a satisfactory working environment for the operator and nearby personnel. Installation works carried out from a wheel loader bucket or the lifting of steel arches by using a telehandler?s fork lift are not acceptable working methods.

Tunnel specific arch lifting equipment comes with a robust and stable tunnel carrier, a telescopic manipulator (ejector) system for mechanised lifting and installation of the steel support, and a basket concept that provides a safe working place for the operators.

As an example, Normet?s Himec 9915 BA uses precision hydraulics on the robotic arm which can handle a steel arch with maximum load of 1,350 kg. The arm can lift the arch, position it precisely and maintain its position fixed. The final fastening of the steel arch to anchors and/or adjoining steel support can then be carried out safely from the basket by the operator(s). The 1,615 kg platform lifting capacity and rotation of 340o makes this archlifter multi-purpose and useful for most man lifting and installation tunnel works. A ?screen kit? for wire mesh installation is one of the most common options.

As another example, the Himec 2000 BAQ (Fig. 2) is well suited for the robotic erection of heavy steel supports in large profile tunnels up to 11 m height and 18 m wide. It has twin erector booms with extensions of 4,000 mm and comes equipped with hydraulically controlled grapples and twin boom and basket systems for man lifting. The maximum lifting capacity of the erectors is 2 x 1,000 kg. Man lifting capacity is 2 x 500 kg. The arch installation work cycle in the railway tunnel for the Sochi 2014 Winter Olympic Games details the pick up of the steel arches from the storage facility (Fig. 2a) and carriage to the face (Fig. 2b).

During the transportation the boom carriage is in its rearmost position and the erector booms are folded to the side of the carrier (Fig. 2c). At the face, the boom carriage is pushed to the foremost position (Fig. 2d) and the ejector booms holding the steel supports are extended (Fig. 2e). Both ejector booms can be operated simultaneously and they allow a precise positioning of the steel support to the tunnel profile (Figs. 2f & 2g). Steel arch positions are maintained by the ejectors until the final fastening of the arch is completed from the two man lifting baskets (Fig. 2h).

The unique robotic concept cuts the cycle time of steel arch installation (two operators) by up to 40-50 per cent compared to single ejector boom units. The safety provided compared to the use of conventional, modified equipment is dramatic and permits halving the crew size at the face.