Vacuum preloading for a truck parking area in Luhtaanmäki

City of Vantaa considers constructing a truck parking area and a filling station on a soft clay deposit in Luhtaanmäki, Vantaa (in Finland). The aim of this study was to evaluate whether vacuum preloading with vertical drains is a feasible ground improvement method for the site. Besides in situ –tests and classification tests, overall 18 oedometer tests were carried out. Preliminary design of vertical drainage was based on Hansbo’s solution, and smear effect was taken into account. Time-settlement -calculations were carried out using tangent modulus method and so called equivalent vertical permeability. In calculations, the following loading history is assumed: First, a surcharge fill of 30 kPa is constructed. After that, vacuum of 70 kPa is applied for 8 months. In order to compensate for the settlement caused by vacuum preloading, embankment load of 10 kPa is later applied. Total settlement is 825 mm, and that considered the final embankment height is 1.2 m. After the treatment, the minimum degree of overconsolidation is 220%. According to the results, vacuum preloading suits well for Luhtaanmäki.