Pezzimenti Tunnelbore is capable of drilling highly accurate, laser-guided microtunnels ranging in diameter from 325mm to 3000mm in ground conditions ranging from sandy clay to basalt in lengths up to and beyond 300m. Pezzimenti Tunnelbore are always adapting, evolving and creating new working solutions for microtunnelling projects.

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Ground Conditions

Ground Conditions account for an estimated 85% of the risk in any microtunnelling project. Good geotechnical information is critical to assess the type of equipment required to be used on the job e.g.  the type of cutters, the need for an outer encasing pipe, the possibility of freeboring in stable ground. All these influence feasibility, difficulty, cost and project risk. The best investment a client can make in a microtunnelling project is obtain good geo-technical information and appoint a good specialist subcontractor to carry out the works.

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Accuracy of +/-10mm at distances up to 100m and +/-40mm at 200m is now standard for the Pezzimenti Tunnelbore system. The confidence for high accuracy allows for flexibility in design and sequencing of the works e.g.

  • The long range targeting of the base of existing manholes on numerous occasions has allowed sewer connections to be made without the need to excavate adjacent to the existing sewer manhole
  • Intercept microtunnels: Drilling from either end of very long runs eg 300m+ has extended the range of microtunnel lengths far beyond that possible for single shots
  • The high accuracy allows the  drilling of “blind” microtunnels i.e. drilling to a dead end which is to be uncovered at a later date. This is required where access to the exit shaft is not possible at the time the microtunnelling is done.
  • Works upstream from the microtunnel, e.g. open cut sections, can be under construction in parallel with the microtunnelling works knowing that the microtunnelling works downstream will achieve the design levels.

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Diameter – Drilling Heads from 325mm to 3000mm

The Pezzimenti Tunnelbore system can microtunnel in all diameters from 325mm to 3000mm. Using a variety of standard microtunnelling head diameters for the great bulk of the works, these standard heads can be readily modified to meet project needs.

All modifications are done in-house based on the known ground conditions and client requirements. Microtunnelling in hard rock such as basalt in diameters as small as Ø440mm is possible. For larger diameters options become possible to remove the spoil using augers or vacuum.

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Length – Long Distance Microtunnelling that Maintains Accuracy

Depending on the ground type and the diameter, the Pezzimenti Tunnelbore microtunnelling system can achieve drive lengths over 400m.

  • Pipejack lengths of over 200m have been achieved.
  • Freeboring in stable ground has allowed lengths of up to 440m to be achieved.

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Pipes – Installation for Water and Sewer

Pezzimenti Tunnelbore has installed a large variety of pipe types for Sewer, Water and Stormwater projects. For Pipejacking the pipe must have a smooth outer wall e.g. Steel, Concrete Jacking pipes, GRP jacking pipes. Freeboring in stable ground allows the use of any pipe type. Carrier Pipes such as PVC, PP, PE, GRP, MSCL are common pipes sliplined into microtunnels.

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Shaft Size

Typically, the smaller the diameter of microtunnel, the smaller the drilling rod is needed. The smaller drill rods are shorter in length and hence a smaller shaft is required. Typical sizes for the shaft are:

  • Up to 460mm diameter – 4m x 2m shaft size
  • Between 461mm – 1000mm diameter – 6m x 2.5m shaft size
  • Greater than 1000m – 8m x 4m shaft size