Operating principle at a glance:
Partial-face Excavation Machines in operation
Partial-Face Excavation Machines from Herrenknecht represent an economically interesting solution in homogeneous and more or less stable soils with little groundwater. Thanks to the simple design, the excavation technology can be easily adapted to changing geological conditions in both loose soils and consolidated rock.
Partial-Face Excavation Machines are equipped with excavators or roadheaders on a project-specific basis.
One machine, two excavation methods
Herrenknecht Partial-Face Excavation Machines can excavate soil using two different cutting tools. The excavator arm has proven its worth hundreds of times in loose soils. Depending on the ground conditions, the universal excavator is equipped with an excavation bucket, ripper or hydraulic hammer.
Rotating roadheaders are used in consolidated rock with uniaxial compressive strengths of up to 80 megapascals. With both techniques, worn tools can be changed quickly and easily.
The soil is removed via belt conveyors or scraping conveyors and conveyor buckets.
Functional principle
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Machine operator's workplace with a direct view of the open tunnel face for precise excavation control.
Direct view of the tunnel face for controlled soil excavation
The machine operator has a view of the tunnel face. This allows him to monitor the excavation very precisely and respond immediately to changes in the subsoil or obstacles (e.g. boulders).
Roadheader or excavator boom removes the soil
Mechanical methods for support, e.g. forward shield or transverse platforms
Belt conveyors or scraping belts provide efficient removal of the muck
Hydraulic thrust cylinders in the shield or a jacking frame in the launch shaft push the machine forward.
Pipe jacking or segmental lining
Partial-face Excavation Machine (ø 11,770 mm) with two cross-bracing platforms, telescopic face plates in the crown and three flexible excavators.
Safe in consolidated rock: Partial-Face Excavation Machines with roadheaders can also be used in geologies with compressive strengths of up to 80 MPa.
Mechanical support of the tunnel face
Partial-Face Excavation Machines are open shield tunnelling machines. They do not have a closed system for pressure equalization at the tunnel face. Instead, various mechanical methods can be used to ensure adequate face support.
To this end, Partial-Face Excavation Machines are usually designed as forward shields with an extension of the cutting edge in the crown area to support the ground.
For additional support of the tunnel face, hydraulically extendable poling plates or breast plates can be used in the crown area. This enables continuous adjustment of the tunnel face support and the angle of repose of the excavated soil.
For larger diameters, transverse platforms can be installed at different levels. They can be equipped with several permanently installed cutting tools to speed up the excavation process.
Compressed air support as an option
In partially water-bearing soils, Partial-Face Excavation Machines and part of the tunnel can be pressurized with compressed air via a lock system. This prevents groundwater ingress. The shield operator's workplace is located in the protected overpressure area.
Simple, safe, and economical breakthroughs
Partial-Face Excavation Machines from Herrenknecht are easy to operate, have low acquisition costs and achieve very good advance rates in suitable ground conditions. Partial-Face Excavation Machines can therefore be a very economical solution for both pipe jacking and segmental lining.
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Steffen Dubé
President and General Manager Herrenknecht Tunnelling Systems USA Inc.
Gerhard Goisser
Commercial Manager Herrenknecht Tunnelling Systems USA, Inc.