Lining with pipe jacking
Pipe jacking
Prefabricated cylindrical elements that form the lining of the tunnel and are installed and driven from the shaft, transferring the thrust to the TBM located at the face.
To reduce friction between the pipe and the ground during the driving phase, bentonite or polymers are injected into the socket and intermediate push stations are installed in long lengths.
There are different types of driving pipes. The most common are:
- Reinforced concrete pipe.
- Steel pipe.
- Polycrete or polyester resin tube.
- Ceramic or stoneware pipe.
The advance is carried out thanks to the thrust provided by a set of thrust cylinders installed in the jacking shaft on the jacking tube, which has been manufactured according to strict standards in order to withstand high longitudinal and transverse stresses without suffering any deterioration.
The pipe placed on the frame will be part of the tunnel once the driving has been completed. Each pipe has a gasket installed in the nozzle, which must guarantee the watertightness, as well as a "dolly" in the tail, which absorbs the possible irregularities of the pipe and allows that this does not suffer when joining two pipes and pushing concrete with concrete.
In all the pits, an attack shaft is built with a reaction wall that will support the thrust pressures of the whole pipe and an arrival shaft where the machine will be rescued. For long pits, elements are installed between the pipes, called "Intermediate Stations", which allow to distribute the stresses among several sections.
