Bucharest benefits of about 66 km metro network, which has been operating for 20 years. There are also extensions under construction, the first 4 km of a total of 11 km will be finished in 2000. Due to the lack of investment funds, about 7 km underground construction has been complete a waiting for the moment when the works will start again. The map from Figure 1 illustrates the underground lines in Bucharest city, having the approximately area of a circle with a diameter of about 22 km. The beginnings of designing (1975) and works for the metro network in Bucharest with the existing technologies (according to the state budget), was based on a great investigation and geological, geotechnical and hydrogeological research for the future metro main lines. In structural design, the interaction between the underground structure and surrounding soils was modeled considering that the soil has hysteresis properties and every soil layer is made from an homogenous and elastoplastic material. The were presumed and then observed phenomena like: the variation of the underground water level, settlements on the ground surface, degradation of some underground structural elements etc., all determined special measures for preventing any kind of structural damages on the surface and underground structures.
From the geological point of view, Bucharest is situated between two views in the central part of Moesic Platform, in the so called Romanian Field, which represents a major depresionary unit, that stretches along the Danube River. The two streams are almost parallel with a NW-SE trend, with old large meanders, close to which there are small depressions in which accumulated the surface waters and the water from the springs situated at the bottom of the slopes. Marshes were formed, that are now hydrotechnically drained.