House connections
Unsteered microtunnelling with the aid of a horizontal thrust boring device
Here steel pipes (lengths between 500 mm and 1000 mm depending on manufacturer), which can be coupled together, are jacked first with the aid of a thrust device. Simultaneously with the jacking, the soil at the working face is excavated and conveyed away mechanically with the aid of auger flights. The drive for the cutter head is located in the start shaft or pit.
Microtunnelling can be carried out in soil and rock subject to the use of the appropriate cutter heads. In water-bearing soils, additional measures such as lowering the level of the ground water are necessary. When the first of the recoverable steel pipes, the external diameter of which is the same as that of the vitrified clay jacking pipes, arrives in the target shaft or pit, the first vitrified clay jacking pipe is coupled with the aid of a transition piece to the last steel pipe that has been inserted and is then itself jacked. In this way the steel pipes are pushed out into the target pit and removed.
Steered pilot jacking mode
In contrast to the previously described unsteered method, an additional phase is used here at the beginning in order to obtain a steering function. A line of hollow steel pilot rods, which can be connected together, is first jacked into the ground from the start shaft or pit displacing the soil. The short lengths of the rods enable them to be removed in a shaft of DN 1000. Monitoring that the system axis is being followed is carried out with the aid of a theodolite or laser system.
Changes in direction are brought about by turning the pilot rod line from the start shaft. When the tip of the first pilot rod has arrived in the target shaft or target pit, a recoverable steel pipe is connected, with the aid of an adaptor, to the last pilot rod that has been inserted. The succeeding steps are as described for the unsteered process.
Underground construction of a house connection to a main sewer
The connection is achieved here with the aid of a 4 phase system:
- Steered drilling from a start shaft to a main sewer with the aid of a line of special steel casing pipes
- Removal of the auger flights and fitting of a diamond core bit and a line of drilling rods. Trepanning of the main sewer with camera monitoring. Removal of the drilling core
- Slip lining of the DN 150 vitrified clay pipe with a special sealing element at the tip of the first pipe. Pressing of the sealing element into the wall of the main sewer with camera monitoring
- Withdrawal of the steel casing and filling of the resultant annular void
Underground construction of a house connection from a main sewer
This process is carried out in 2 phases as with the unsteered horizontal thrust boring process.
The thrust boring unit is fitted in an existing sewer or tunnel and can be aligned for any inclination up to 90".
The minimum size for the installation of the jacking unit is a man sized main sewer of at least 1200 mm. The unit is transported through the pipe on a trolley to the previously surveyed connection point. The opening for the jacking process is produced by trepanning. On the completion of work, the annular space remaining between the pipe and the trepanned hole is sealed in a watertight manner with the aid of a specially designed rubber link chain.