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Offenburg
Requirement
tunnelling project
 |
Employment | Sewage |
|---|---|---|
| Geology | Sand and gravel shot through with loam | |
| Tunnel Length | 286 m, 405 m, 159 m | |
| Diameter | 1,980 mm |
Solution
machine data
| Machine Type | Partial Face Excavation | |
|---|---|---|
| Support Techniques | Pipe Jacking | |
| Cutterhead Power | ||
| Torque | 33 kNm |
It was necessary to proceed extremely carefully with the demanding second of three retensions: the foundations of the Trinity Church in Offenburg, South Baden, had to be passed under with an overburden of only 3.5 meters. So that the two 50 meter high church towers of the over 100 year-old building did not develop a tilt, the work was preceded by intense geological examinations. The new channel collects up to 85% of rain and contaminated water, and conveys it to the sewage treatment plant.
The solution was a Herrenknecht machine with partial face excavation, which tunnelled the mixed water channel using Pipe Jacking technology. To avoid settlement, a bentonite suspension immediately behind the shield supported the so-called intersection (the excavation cross-section is somewhat larger than the tunnel diameter). On June 23, 2006 the machine completed the second stage of its work, having driven 405 meters through loam and sand with a diversion of less than one centimeter and with no damage to the church. Building work was completed at the end of 2006.
