FIELD: building industry, particularly initial structure building. SUBSTANCE: initial structure includes starting mounting chamber formed by open-cut method. Mounting chamber comprises tray, transversal end walls with windows, front and rear longitudinal solid side walls having metal insulation on outer surfaces thereof. Metal insulation is formed of elongated corrugated grooved panels connected with tray waterproofing means for creation of waterproof shell. Walls consist of inner monolithic reinforced concrete layer, elongated corrugated grooved panels with filled voids and outer protective concrete layer combined in integral unit. Longitudinal walls are supported in chamber central part by transversal hold-down beams arranged in two layers in upper half of wall heights. The last transversal wall is located in joining area between mounting chamber and tunnel part formed by closed method. Head end of said tunnel part is located into pre-formed concrete unit built into soil and having strength equal to 15%-35% of lining strength of the tunnel head part. Concrete unit length is not less than one-third of mounting chamber length. EFFECT: increased structure strength by cooperation of initial structure and closed tunnel part built into soft ground including watered ground, possibility of optimal material distribution by tunnel parts load, increased strength in tunnel head part, providing of tunneling machine accurate and stable position in tunnel head part, prevention of deformation in tunnel head part and as result prevention of deformation of buildings and installations located near tunnel building site. 13 cl, 16 dwg
