Die geologie des Münchener untergrunds und seine bedeutung für die baugrundmodellbildung in städtischen gebieten

The City of Munich is situated in the Alpine foreland of Bavaria in southern Germany and forms the core of a fast growing urban region. The geology of Munich is dominated by loose alluvial, fine to coarse grained sediments of Neogene and Quaternary age. The Munich gravel plain comprises sander terraces formed during the Pleistocene glacial periods as well as the modern floodplain of the river Isar. With a major disconformity and a hiatus of several million years, these rather young gravel terraces cover Neogene Molasse deposits of the Alpine foreland basin. These are of fluviatile and lacustrine facies and commonly composed of clay, marl, sand and, locally, gravel. In the past decades numerous underground structures (e.g. subway tunnels) were built leading to a detailed knowledge of the geology. Nevertheless, the multiphase geological history (e.g. climate changes, weathering, erosion and accumulation, early diagenesis) and the complex sedimentary architecture in combination with new construction methods constantly raises new geotechnical challenges. Requirements for geological site investigation and ground modelling thus are very high, especially in the very sensitive urban area. The geological conditions and geotechnical consequences are quite similar to those encountered in many other urban areas worldwide, e.g. in cities in major flood-plains, in coastal areas or forelands of mountain belts. The objective of this paper is to highlight major aspects of ground modelling in Munich and to provide insight into the interplay of geological history and geotechnics. In detail, the engineering geological significance of the ground model data will be outlined. This includes the structure of fluviatile sequences, sediment types, erosive and weathering features, petrographic composition, diagenetic effects, discontinuities as well as the complex hydrogeology. By means of examples, the need for comprehensive ground models that summarize the total of geological history will become evident.