No-dig technology characterized by a closed excavation front in which the excavation section coincides with that of the shield which guarantees the mechanical support of the soil
Microtunnelling is a jacking method using a tunnel boring machine without an operator at the excavation face for jacking pipes between two shafts, which is remotely controlled from a control room placed on the surface.
This system allows the installation of pipelines with a drilling diameter range between 350 mm and 3,600 mm.
- Operation in the presence of groundwater
- Directional control and guidance system
- Hydraulic clearing system
- All types of terrain
- No presence of the operator on the excavation front
A technology fitted for almost all types of terrain
The system consists of a cutting head crushing the soil, which, thanks to the head rotation, is conveyed to the spoil ring. The head is provided with suitable excavation tools, which vary according to soil characteristics. The cutting head is also provided with a directionable articulated joint allowing us to “guide” the head during boring by means of suitable, remotely controlled hydraulic jacks.
The second essential element of Microtunnelling is the jacking unit located in the shaft (therefore called jacking shaft), which allows us to drive the pipes in the tunnel bored by the cutter head. Pipe driving occurs thanks to the pressure exerted on pipes by the main jacks, which are contrasted by the jacking shaft wall that shall therefore be of a suitable dimension. The thrust on the cutting head is transferred from the pipes, on which acts the force exerted by the jacking unit itself.
Microtunnelling uses hydraulic spoil removal machines (slurry machines) provided with a cone- shaped crusher allowing the excavated material to be crushed and conveyed into a chamber placed behind the cutting head (excavation chamber), from which the material is pumped in the form of fluid (slurry) into the separation plant located on the surface. Mechanical spoil removal machines are rarely used.
The characteristic of the perforation supported by the hydraulic mud, makes it possible to use microtunnelling in any type of terrain, from clays to silt, from loose soils to rock and even in the presence of groundwater.