Subsoil investigation - Difficult conditions due to old buildings

Difficult conditions due to old buildings

On a car park of the Kiel University of Applied Sciences in Schwentinestraße / Grenzstraße, the GMSH is planning the construction of a new institute building for the courses of study in civil engineering and architecture. The scope of services includes a subsoil investigation to assess the soil, a foundation recommendation and information on the earthworks and shoring. Six small pile-drillings and seven pressure soundings were planned in May 2023 to determine the soil structure.

Through historical research it was known that the site had been built on since the end of the 18th century. From about 1876 to 1984, the site was used by the Howaldts shipyard. During World War II, most of the buildings were destroyed and rebuilt in the 1950s.

In the course of previous contaminated site investigations from 2020, massive drilling obstructions in the form of floor slabs and foundations were already identified throughout the investigation area. In addition, two air raid shelters from the Second World War were known to be located underground. Based on the results of the historical research and the site plans available to us, the planned exploration points were placed between the still existing foundations and air raid shelters.

In the run-up to the subsoil investigations, the planned drilling points were cleared by an explosive ordnance disposal service, as explosive ordnance is suspected in the entire investigation area due to dropped munitions. In the course of these deep soundings, massive drilling obstacles were encountered on the investigation area, which could not be identified in the available plans. 

Accordingly, the subsoil investigations turned out to be difficult. Due to the obstacles in the subsoil, the explorations had to be stopped and moved several times. With a bit of luck, the drilling team succeeded in carrying out four small ram drillings and three pressure soundings. The project shows us that despite existing information about the history of the area and plans of old buildings, it can never be ruled out that there are still other unknown obstacles in the subsoil and that these lead to more difficult conditions in the course of the investigations.