PARAMETERS & DESIGN

  • Trenchless solution
  • No disturbance on the surface (traffic, river, buildings)
  • Available in all soil conditions (rock, clay, silt, gravel)
  • Wide range of diameters (250 – 3000 mm) using upsize kit and modified cutterhead
  • Usual length of trajectory: 600 m
  • Pipe materials: reinforced concrete, GRP, polymer concrete, steel
  • More economical and eco-friendly compared to open ditch construction
  • Less earthworks, less transportation, less carbon dioxide emission
  • Precise navigation system (less than 20 mm deviation)
  • Vertically and horizontally versable trajectory
  • Available below groundwater level – No need for dewatering
  • Designed launching and reception shafts
  • Main technologies depending on soil: AVN (Automatic Wet Tunnelling) and EPB (Earth Pressure Balance)
  • Equipment supplied by Herrenknecht since 1999

AVN Technology

The automatic wet tunnelling technology applies a hydraulic slurry circuit. Soil is excavated by a cutterhead matching the respective soil type ranging from silt to rock. Excavated rocks are crushed inside the excavation chamber, and advance to the suction port, where the material is mixed with water, and is removed by pumps.

EPB SHIELD Technology

The Earth Pressure Balance technology is ideal for soft clay and silt soils. The homogeneous excavated soil is used as support medium. In the excavation chamber, the excavated soil is mixed into a paste, which is used as a pressure medium. Balance is achieved by controlled advancing and soil removal though screw- and belt conveyors.

GEOTECHNICAL CONDITIONS

TYPE OF CUTTERHEAD

Permeability Factor (m/s)
Clay Silt Fine Sand Medium Sand Coarse Sand Fine Gravel Medium Gravel Coarse Gravel Stone/Rock
10-11 10-10 10-9 10-8 10-7 10-6 10-5 10-4 10-3 10-2 10-1 1 10

JOBSITE AROUND THE SHAFTS

Shafts are constructed at the starting (launching) point and end point. The microtunnelling equipment, the frame of hydraulic cylinders and all pipe sections are craned into the launching shaft. The size and depth of the shafts depend on the launching equipment and future utilization of the shafts. They are propped by heavy brackets, Larssen slabs or piles.

UNIVERSAL NAVIGATION SYSTEM

Tunnelling is laser guided, which allows less than 20 mm deviation. In case of lengths of more than 400 meters, the system is supplemented with a hydrostatic water levelling system. The system is also capable to bore curved trajectories. In this case and above diameters of 500 mm, a gyroscopic navigation system is applied at pipe jacking.

ELS

Electronic Laser System

(straight drives < 200m length)

ELS-HWL

ELS with Hydrostatic Water Leveling

(straight drives < 400m length)

GNS-P

Gyro Navigation System for Pipe Jacking

(curved driven tunnel diameter > 500mm)

LUBRICATION & INTERJACK STATION

In order to provide quick and smooth launching, bentonite is pumped through outlets on pipe segments designed to lubricate the external surface of pipes. In case of extensive lengths, the launching station is supported by an interjack station that provides additional power to supplement the launching system.

Lubrication

Bentonite is pumped through outlets on pipe segments to ensure suitable skid between the soil and the pipe surface.

Interjack station

In case of extensive lengths, an interjack station is built in the system to make sure power is suitably balanced.

ARE YOU INTERESTED?

We are offering you the advantages of trenchless public utility construction. Please do not hesitate to contact us, and we’ll provide you with the best solutions for your civil engineering project.

+36 1 883 1440





COLAS ALTERRA THANKS HERRENKNECHT AG FOR PROVIDING ILLUSTRATIONS AND PHOTOS FOR THIS WEBSITE