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1. Application
GRUNDOBORE 400 is a robust installation unit for the non-steerable and steerable installation of product and protection pipes up to OD 406. The unit is characterized by high installation accuracy, which is for example required when building sewers or installing pipes under railway tracks.
2. General conditions
A launch and a target work pit or a launch and a target manhole are required on the jobsite to operate the GRUNDOBORE 400.
3. Mode of operation
The GRUNDOBORE 400 is lowered into the launch pit or manhole. An external hydraulic unit provides the hydraulic driving power for the GRUNDOBORE 400.
The steered boring process proceeds in three different phases:
Phase 1
The GRUNDOBORE 400 presses the pilot rods right-on-target into the soil while rotating continuously using the displacing method. The single pilot rods are screwed together successively, each rod being connected to the last rod sticking out of the soil. One of the two measuring systems is switched on before the steering head is pushed into the soil. This allows permanent observation of the measuring system while the pilot rods are slowly pressed underground with slow rotating motions. With every deviation from the bore path, rotation is stopped, the pilot rods are pressed forward carefully until the rods point into the right direction again. The slanted steering surface of the steering head makes these path corrections possible. Once the rods are repositioned, rotation can start anew. The first drilling phase is completed when the pilot rod arrives at the target pit.
Phase 2
At the beginning of the second phase, the guide bearing is screwed on to the last pilot rod. Then the shoe pipe with the first inserted conveyor screw is lowered into the launch pit together with the bore head and screwed together with the guide bearing. Now all remaining retrievable pipes, including the conveyor screws, are inserted and pushed in.
Together with the bore head and conveyor screw, the retrievable pipe transports the soil into the launch pit. At the same time, the retrievable pipe pushes the pilot rods into the target pit, where they are unscrewed and recovered successively. Simultaneously the retrievable pipes are screwed together one by one in the launch pit and then pressed forward. The outer diameter of the retrievable pipes is identical with that of the product pipes, therefore the tunnel generated underground is ready to fit them in.
Phase 3
Finally the product pipes (e.g. stoneware thrust pipes) are pulled into the soil. A transition piece helps to establish a firm connection between the last retrievable pipe and the first product pipe. While the product pipe is being pressed into the bore tunnel, the retrievable pipes are unscrewed and recovered successively in the target pit.
Advantages:
- High installation precision
- Drilling tools can be changed in strongly varying soils or replaced when worn
- No intermediate pits
- No disruption (loosening/packing) of the enclosing soil formation
- Thin cover due to only slightest soil displacement
- Pressings up to approx. 60 m
- Applicable according to the latest technical standards
- Friction-free
- Solid construction, suitable for all site conditions
- Extension of the pressing frame possible
- Choice between two location systems (laser or vision theodolite)
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