In spring 2017, Holland Drilling performed an HDD drilling operation under the Autobahn A6 in Heilbronn, Germany. The Autobahn A6 was being modified, and the relocation of existing cables and pipelines was part of this extensive project. Near Heilbronn, a completely new bridge is being constructed, requiring the existing cables and pipelines to be relocated first. The client chose to route all utilities through a single 20″ steel casing pipe with external concrete coating under the A6 using HDD drilling.
The ground conditions and design made this drilling operation challenging. Due to limited space, the drill line consisted of multiple combined curves with a minimal radius. The alternating soft layers (loam) with boulders followed by hard rock layers made following the drill line particularly difficult.
Holland Drilling deployed their 80-ton drilling rig for this project.
A mud motor was used for the pilot bore. Subsequently, hole openers were used for reaming to achieve the desired tunnel diameter in the present rock formation. Despite these conditions, the drilling was completed within schedule, and the 20″ steel pipe was pulled in with minimal tensile force.
