Prior to a major renovation project and the construction of a hotel, the foundations of the historic building Draken on Järntorget in Gothenburg needed to be reinforced. The property was built in the early 1950s and the foundations were piled with timber, which over time has begun to rot, causing the foundation to be compromised. Many cities are built on timber piles and they work well until they are exposed to oxygen. Soil conditions have a major impact, but densification of cities may have an effect as well. New buildings, road construction and new landscaping near house facades disturb the soil conditions which in turn impacts the timber piles meaning that the foundations will often require reinforcement.

The obvious choice

Project supervisor Richard Hammar of Grundia AB stated that the Draken project lasted about seven months. Early in the planning process, several challenges emerged, which resulted in a demolition robot being the only solution for the job. “Some areas in the building are confined and sometimes difficult to access, the size, power and flexibility of the Brokk made it an obvious choice,” says Richard.

Since the work was to be carried out in a basement, the requirements were specific. The robot needed to get through narrow passages (less than 800mm) as well as travel up and down stairs. The Brokk 200 delivers maximum power in relation to its size, which was crucial as the task required the use of a large hydraulic breaker in a limited space. As the Brokk robots are remote controlled, the operator has the opportunity to manoeuvre the robot from a safe distance allowing the best possible view of the work. As the project was carried out entirely indoors, an electric powered machine was essential.  The exhaust fumes from a diesel powered machine would have made the work environment unbearable.

A flexible solution

A Brokk robot is incredibly versatile thanks to the ability to use different attachments. When piling, the choice of hydraulic breaker may differ depending on the soil conditions and the state of the building; in this particular case a breaker with a large diameter piston was needed. When using a heavy breaker, the robot needs a counterweight for good stability. With these types of jobs, where there is limited space and limited ceiling height, a side mounted breaker made it possible to maintain a high working pace. In addition, this type of breaker made it possible to maximise the length of each pile.

About the project

In total, Grundia AB laid 303 piles on the building's 1,500m2. The average depth was about 41m but varied between 17m and 70m. Due to changing ground conditions, some piles could be driven quickly, and others took several hours. For the deepest piles, the first 40m took about two hours, while the remaining 20m took almost four hours. In this project, Brokk 200 was used for a total of 1,500h.