Simultaneously a new product pipe of the same or a larger diameter is introduced. The used pipe materials usually have smooth outer contours and a protective layer: PE-HD pipes with extruded protective coat or steel pipes with fiber cement coating as long pipes. Furthermore, short pipe modules made of PE-HD and PP are used.
Several types of pipe bursting are available. During dynamic bursting a pneumatically driven soil displacement hammer with a cross-section larger than the old pipe is propelled through the existing pipe. The hammer has an expansion or cutting head on one side.
In order to prevent the hammer from deviating from the existing piping line, it is coupled to a capstan winch and tensioned. In this method the tunnel is expanded by boring with the soil displacement hammer.
During static bursting the expansion or cutting head is pulled through the old pipe using hydraulic leverage and without causing vibrations. During caliber bursting the outer diameter of the new pipe is less than the inner diameter of the old pipe. The old pipe is displaced only in areas where it is damaged due to displaced joints, fractures or by penetrating fragments.
Fields of application::
- Depending on pipe material also suitable for pressure and non-pressurized pipes
- Sewerage and industry
- Circular profiles
- For old pipes made of stoneware, asbestos cement, grey cast iron, plastic or unreinforced concrete as well as steel and ductile pipes
- Nominal size range from DN 80 to DN 700 or from DN 150 to DN 1000 for caliber bursting
- Depending on geological conditions, the cross-section can be enlarged in comparison to the old pipe
- Suitable for all types of damage – and to a limited extent also for collapsed pipes (after preliminary rehabilitation as required)
- The pipeline route must be straight
Advantages:
- Short construction time
- No cross-section reduction
- Cross-sectional expansion possible by one dimension
- Standard pipes and components with defined material properties
- Introduction of segment pipes: via existing shafts
- No preliminary works such as cleaning or removal of obstacles in the pipe required
- The result is comparable to the installation of a new piping system
- High durability of the new channel and the new connections
Disadvantages:
- Only possible in compressible types of soil (pipe zone) and above the groundwater (groundwater drainage can be required)
- Appropriate pipe bedding required (not for pipes with concrete coating; hollow spaces, low bulk density cannot be compensated)
- A minimum overlap of usually 2m or threefold to sixfold of the pipe diameter is required (depending on which of both is greater)
- Minimum distance to other structural works and adjacent exterior facilities (e.g. gas, water and heat supply and traffic facilities) must be complied with.
- Depending on machine size and in the case of pulled-in pipe string, a starting trench is required.
- Connections may only be made from outside via trenches.
- In the case of segmented pipes, lateral connections are not possible in the area of pipe joints (route of connecting pipe can be subject to modification)
- A detailed geotechnical report is usually required.
