GRUNDOBORE 200S is an auger boring unit for the underground installation of product and casing pipes up to OD 279mm. It is particularly suitable in confined spaces because the stabilisors and the drill-thrust unit can be installed separately.
Launch as well as a target work pits or manholes are needed on the jobsite to operate the GRUNDOBORE 200S.
The GRUNDOBORE 200S is lowered into the launch pit or manhole. An external hydraulic power unit provides the hydraulic driving power for the GRUNDOBORE 200S.
Steered boring passes through four different stages
The GRUNDOBORE 200S works with a hollow drill bit and a swivelling drill bit guide to bore a core hole into the manhole wall. The hole is spot bored into the wall of the manhole in the exact position of the intended bore axis. When working from out of a work pit, phase 1 is dropped.
Then the GRUNDOBORE 200S works with the displacing method to press the pilot rods pinpoint into the soil while rotating slowly and continuously. This is performed with the steering head first, followed by the single pilot rods which are screwed together successively, with the next rod being connected to the last rod sticking out of the soil. The measuring system shall be switched on before the steering head is pushed into the soil. It allows the operator to supervise the measuring process constantly while the pilot rods are being pressed underground with slow rotating motions. With every deviation from the bore path, rotation is stopped and the pilot rods are pressed forward carefully until the desired direction is taken again. The slanted steering surface of the steering head makes these path corrections possible. Once the rods are repositioned, rotation can start anew. On arrival of the pilot rods at the target pit, the second drilling phase is completed.
In the 3rd phase, the steering head is disconnected from the pilot rods and replaced by a retrievable pipe with the first inserted conveying screw and the bore head. This assembly is lowered into the target manhole and screwed together with the first pilot rod. Under continuous rotation, the pilot rods are pulled back successively from the target manhole in direction of the launch manhole. The linked retrievable pipe is pulled in at the same time; the retrievable pipe with conveyor screw reams back the soil into the launch manhole in process.
The single pilot rods appear in the launch manhole, ready to be unscrewed and recovered. Simultaneously, the retrievable pipes are screwed together at the target manhole, section for section, and then pulled in.
Finally the product pipes (i.e. PP jacking pipes) can be pulled underground, starting from the launch manhole. A transition piece helps to establish a frictional connection between the last retrievable pipe and the first product pipe. These are now pulled into the soil at the same time. In the launch manhole, the retrievable pipes are screwed apart one by one and recovered.