Geotechnical investigation and static analysis of deep excavation walls – a case study of metro station construction in Warsaw

Abstract The paper presents detailed analysis of the case – a construction of deep excavation of metro station in Warsaw. Basing on this example, the great impact of the accuracy of the geotechnical investigation on the static analysis of diaphragm walls is discussed. Geotechnical studies for the construction of the central section of the second metro line were carried out in stages. Basic geotechnical soil investigation took place in the first stage of investment process, e.g. building permit and tender design stages in 2003–2004, 2007 and 2010. In subsequent years, complementary soil investigations have been performed by the contractor, and the results occurred to differ significantly. In the first part of the paper detailed description of the case is introduced. The geological conditions in the area of the station and the interpretation of the results of the three successive stages of geotechnical investigation are presented. As a result, two locations were selected with a great diversity of the soil profile depending on the stage of investigation. For each location, detailed, multiple static analysis of diaphragm walls were performed, taking into account changes in the soil profile. In the paper, one selected location is described in detail. The discussion of calculation results for this location in relation to the changing geotechnical data is presented and final conclusions are provided.