Vincent Keller, dirécteur général at Durmeyer, explained: "There were a lot of challenging aspects in this project in Département Haut-Rhin. The space was very confined and there were also train tracks located very close to the drilling operations.

"In addition to this, we also needed to make sure that the groundwater was sealed off during the entire operations. All these issues and also the fact that the construction soil contained stones over 25cm diameter made us decide to use the twin rotary system method with a BG 36 from Bauer."

The twin rotary system combines the CFA method using a continuous flight auger with provisional casing. The result is a cased borehole created with a continuous flight auger or hollow stem auger.

"This method is particularly advantageous in areas with high groundwater and soil that are in danger of being lifted, and require drilling under water load during Kelly drilling," explained Tim Lämmle, managing director of Bauer Machines SAS, the French sales subsidiary of Bauer Maschinen GmbH.

In this project, the casing used in the twin rotary system means that erosion of soil underneath the train tracks could be avoided and perfect verticality of the piles could be guaranteed.

"Because the method can be used with many different soil conditions and the BG 36 is so compact compared to its performance we also see plenty of possible future applications," continued Keller.

Despite a more complex installation (compared to Kelly drilling or drilling with a hollow stem auger), the drill rig is very efficient and the safety aspects also played an important role: "In particular the material ejection system, with chute and drilling bucket, offers our employees a high level of safety and comfort. It's impressive how safe working on a construction site can be these days."

Durmeyer and Bauer have had a business relationship for over 30 years. At the moment, in addition to the BG 36, Durmeyer also has a BG 20 H, a BG 36/40 and an RG 22 S from RTG Rammtechnik GmbH in its machine fleet.

"Once again with this project we were very impressed with the support we received from Bauer," said Keller. "Extensive operator training and expert on-site support meant that we were able to operate successfully from the very first pile. We benefited a lot from the experience that Bauer has." Last but not least, the building owner, SIVOM, was also more than satisfied with the performance and project result, making Keller confident that "we will definitely continue to use the method in the future."

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