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Microtunneling / Open shield technology

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Method
Both methods are a pre-qualify contractor for difficult pipejacking projects. The pipe is inserted from the entry and pushed behind the machine. The equipment can be moved from launch pit to target pit via hydraulic pressed jacking frame. Both methods can be made very long borings with in big diameter as well (intermediate Jacking Stations could be necessary), with minimal impact in urban situations.

Lubrication
To help reduce the jacking forces along the pipe, a lubricant must be injected into annulus space around the pipe. It is very important to define the adequate lubrication stuff (Bentonit). The stuff is mixed in the bentonite mixer. After that it’s pumped trough injection stations between the pipes and tunnel wall.

Microtunneling

Microtunneling machines have now been developed to work from drive shafts in almost all types of ground conditions. Careful constructability analysis is needed, and an appropriate Microtunneling method and cutting head should be selected in order to achieve successful completion of Microtunneling projects.

Accessory parts of a Microtunneling System: Control Container, Soil Separation Plant, Slurry system, Lubrication Plant, supply pumps.
The machine is made because of the earth- and mechanical pressures with a pressurized front end. Alternatively, water or bentonite may be used to convert the soil into slurry at the cutting face. The slurry is then pumped to the surface where the solids are separated before disposal. Both systems provide face support by mechanical earth pressure balance. Slurry pressure at the face can also be used to combat external ground water.

The operator controls the machine from a control room on the surface of the ground.
The operator is given constant feedback about the machine’s location, orientation and hydraulic devices via a computer console.
The machine also has video cameras set up to give the operator more information.
The operator can then control the MTBM and the jacking frame from the safety of the control room.


  • Closedface shield using slurry to remove excavated soil


  • Positive face support in unstable soils and under groundwater


  • Remotecontrolled; no man entry


  • Highly accurate guidance systems


  • Many jacking pipe options

Open shield technology

The open shield tunnel boring machines are developed for tunnel excavation or milling in various earth mechanics.
This kind of machine has a cutting arm which comprises a rotating cutting head or an excavator on the front end. The arm is mounted so as to be vertically and laterally pivotable. The machine is provided with a loading table, which is disposed on the moving gear frame at the front below the cutting arm, and a central conveyor which extends from the loading table to the carriage. The conveyor moves the muck into mine-wagons which are carrying out the soil on tram-road.

Tunneling with this method is limited by size: tunneling involves personnel working inside the tunnel.

Tunneling is thus limited to a size big enough to work in, generally larger than 150 cm.

Smaller-diameter pipe installations can be completed by our other methods.

This variation has the advantage that it is an operator in the machine itself. The impediments can betimes be shown. The problems or corrections can be handled directly from inside (machine stop, cutting head change, etc.), no digging will be necessary.

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