This paper describes the compilation, contents and use of the City of Helsinkiís geotechnical data in
city planning, engineering design and building supervision. These operations have continued in the same way for nearly 50 years. This has made those who engage in underground construction and in city planning familiar with the cityís foundation engineering and underground construction resources. Therefore there has been little damage in constructi on to date, even though Helsinkiís geotechnical conditions are demanding from the perspective of foundation engineering and tunnelling.
Helsinki (0.56 million people) is located in a variable region with respect to soil conditions, in which
bays, soft clay areas and steep rocky outcrops alternate. 35% of the cityís surface area of 185 km≤ consists of soft clay residue from the ice ages (shear strength s = 5-15 kPa and water content w = 50-150%) (Figure 1). The thickness of the soil cover is usually 5-30 metres. Precambrian bedrock contains weakness zones. Groundwater surface is at a depth of only 1-3 metres.