ABSTRACT
In the field of geotechnical engineering, risks that materialise can have a significant impact on the serviceability and stability of a geotechnical structure, as well as its construction timeline. Additionally, these risks can potentially affect the surrounding environment. Those risks arise not alone from variable and complex characteristics of the subsoil and groundwater, as well as from design and modelling of the soil-structure interaction, but also from execution process. Hence, risk management must identify various sources of risk and conduct risk analyses to assess the probability and consequences of undesirable events. Risk control and mitigation measures should cover all stages of ground investigation, geotechnical interpretation, design and construction. These aspects are explored and reflected on the collapse of the Historical Archive of the city of Cologne as an example. On March 3rd, 2009, the collapse of the archive and adjacent buildings occurred during the construction of the new North-South metro line. This incident caused significant damage to the city of Cologne, but also affected the underground construction sector in general. With a total damage sum of around 1.2 billion euros, it stands as the most severe accident on a German construction site to date. The investigation of the damage evidence was a technically challenging task that lasted more than twelve years. It involved numerous steps, including the construction of a 34 m deep investigation shaft. Based on these experiences the consequences for the independent checking of design and execution, for the quality assurance of underground works and their supervision, but also the need for a risk prevention based on communication and partnership between all parties involved in the construction process is reflected.
