Large-gradient underground station double-layer channel step-type lining construction method and structure

The invention discloses a large-gradient underground station double-layer channel step-type lining construction method and structure. After double-layer channel preliminary supports (1) are completed,reinforced concrete of low-layer channel bottom plates (2) is constructed firstly; step-type small side walls (3) are constructed on the two sides of low-layer channel side walls (4); and then combined steel formworks are erected, and reinforced concrete of the low-layer channel side walls (4) and reinforced concrete of low-layer channel top plates (5) are constructed. After a lower-layer channellining is completed and reaches the designed strength, upper-layer channel small side walls (6) are constructed on the two sides of upper-layer channel side walls (7); and then split spliced-type simple formwork trolleys are assembled and erected, and reinforced concrete of the upper-layer channel side walls (7) and reinforced concrete of upper-layer channel arched parts (8) are constructed. According to the large-gradien