Honeycomb excavation process
Soil remediation on a new scale in Ingolstadt
A new 60 hectare technology park is being built close to the headquarters of Audi AG in Ingolstadt on the site of the former Bayernoil AG refinery. With this ambitious project Audi is creating space to develop new technologies for the mobility of the future. But first the joint venture AUDI IN-Campus GbR (comprising ZÜBLIN Umwelttechnik GmbH, Geiger Umweltsanierung GmbH & Co. KG, Wilhelm Geiger GmbH & Co. KG and STRABAG Umwelttechnik GmbH) had to clear the site of contamination. In addition to preventing flow-off so as to protect the Danube floodplains, a combination of three methods was used for this: air sparging (a process to remove volatile contaminants using pressurized air), honeycomb excavation (a soil replacement process) and a soil washing facility. A müller vibratory hammer played an important part in the project.
For the honeycomb excavation process, the experts came up with the idea of mounting a free-riding müller MS-40 HFV vibratory hammer from thyssenkrupp Infrastructure on a Liebherr excavator. The engine power of the excavator was sufficient to also power the hammer, resulting in a highly mobile and efficient leader-guided driving system. Using the müller vibratory hammer, the steel honeycombs were driven up to 12 meters into the contaminated soil over 25,000 times. In this way roughly six hectares of the worst-polluted site area were freed of contaminants. In view of the difficult soil conditions, the idea of converting the free-riding hammer to a leader-guided version proved highly successful. The combination of the müller vibratory hammer and the Liebherr excavator generated such power that the geology of the soil with its Danube gravel was no longer a significant problem. Free-riding systems use the weight of the vibratory hammer – in this case around 14 tons – to drive the steel honeycombs into the ground. But with the excavator it was possible where required to apply up to 50 additional tons.
The site was set up in June 2017 and the first steel honeycomb driven into the soil in August 2018. That marked the start of a cycle that continued for two years: the vibratory hammer drove six to seven steel honeycombs into the soil, then the crawler-mounted excavator with a grab extension and a clamshell grab adapted to the geometry of the honeycomb removed the contaminated soil from the honeycomb for transportation to the washing facility. During excavation, the extension was rotated repeatedly by one sixth to ensure all corners of the honeycomb were emptied. Once the soil had been excavated from three to four honeycombs, a wheel loader then backfilled them with cleaned soil from the washing facility. The time between excavating and backfilling had to be kept short due to the groundwater. As soon as a honeycomb had been completely backfilled, it was extracted using the vibratory hammer and then driven directly into the soil at the next point. As a result, the leader-guided müller vibratory hammer was in constant use on the site.
The MS-40 HFV hammer mastered the long operating hours with ease – both with regard to heating up during continuous use and stability of performance. müller vibratory hammers are highly versatile – free-riding for small projects and leader-guided for major jobs.