The tunnel boring machine is composed of a steel cylinder equipped with a hydraulic excavator in the front. The material taken by the excavator is evacuated using a conveyor or an auger. As the excavation work progresses, the tunnel borer is pushed forward while a liner plate is installed in the rear section of the tunnel borer. Cement grout can be injected throughout the process in order to fill the annulus between the pipe and the adjacent soil.
The drilling alignment is continually checked using a laser incorporated into the tunnel borer and a correcting head makes it possible to make adjustments during the excavation process. Moreover, a shield can be installed in the upper part of the tunnel borer, which makes it possible to avoid any excess excavation that might produce subsidence.
The tunnel borer is used in granular soil for tunnels extending up to 2400 millimetres in diameter.
We should point out that we have our own tunnel borers, which we manufacture directly in our workshops.
Pipe jacking is a technique which consists of driving in concrete conduits under an obstacle. The equipment needed to accomplish such work is composed principally of a tunnel boring machine and a jacking station.
The tunnel boring machine is first of all driven into the ground supported by the concrete conduits, which are pushed directly behind it using the jacking station. These concrete conduits, manufactured expressly for this type of work, do not have any bells and allow a direct contact between the entire periphery of the conduit and the ground. Once the work completed, cement grout can be injected to fill any cavity that may have been created.
Afterward, the material is removed using an excavator incorporated inside the tunnel borer, which sends the material out through an auger and is collected outside by a conveyor. Finally, a corrective head, located in front of the tunnel boring machine, makes it possible to make the necessary corrections in accordance with the proposed plan.
This technique makes it possible to replace an existing conduit with a polyethylene conduit. In order to do it, a specially designed air hammer is first of all introduced into one of the extremities of the conduit to be replaced. Then a cable fixed to the air hammer is inserted into the existing conduit and connected to a winch located at the other extremity of the segment to be replaced.
The replacement conduit is first of all fused into its complete length and attached behind the hammer. Therefore, the installation of the new conduit progresses in accordance with the advancement rhythm of the hammer and no excavation is required.(Click on the image for an enlarged view)