Recently a new Extension of the Madrid Subway (Spain) is carried out (1995-2003). In 8 years more of 105 Km of tunnels are builded by several procedures: Traditional non-mechanized excavation, precast linings by E.P.B machines, cut and cover system, etc. In this paper the basic criteria adopted for the design of tunnels and stations built with the cut and cover method (reinforced concrete continuous and discontinuous walls) are analysed. Initially, to this purpose the geotechnical properties of the Madrid ground are reached, in order to establish a group of unified desion geotechnical parameters. The hypotheses made for the numerical analysis of in situ walls are shown (calculation model, water pressures, etc), together with the installed instrumentation and the obtained results
