Reinforcement system at railway tunnel section passing through karst cave with large dip angle and construction method

A construction method of a reinforcement system at a railway tunnel section passing through a karst cave with a large dip angle, specifically comprising:

• (I) building a protection at a top of the tunnel
• building an umbrella arch (1-1) at a top of a portion, passing through a karst cave, of a main tunnel (1), filling a top of the umbrella arch (1-1) with plain concrete to form a concrete layer (1-2), stacking a sandbag on the concrete layer (1-2) to serve as a flexible buffer layer (1-3), and pouring reinforced concrete at a top of the flexible buffer layer (1-3) to form a protective layer (1-4);
• (II) building a foundation pit
• excavating the foundation pit (3) at a bottom of a portion, passing through the karst cave, of the main tunnel (1);
• driving, after excavation, anchor cables (3-14) into walls of the karst cave on a periphery of a bottom of the foundation pit (3) for fixing, wherein a free end of one anchor cable (3-14) and a free end of another anchor cable (3-14) driven into an opposite wall of the karst cave are fastened together by a buckle (3-15);
• and
• erecting reinforced beams on the periphery and in a middle of the bottom of the foundation pit (3), wherein the anchor cables (3-14) are located at halves of heights of the erected reinforced beams, pouring concrete to form a ring beam (3-11) and an intermediate beam (3-12), pouring concrete in a space between the ring beam (3-11) and the intermediate beam (3-12) to form a pad layer (3-13), and building a foundation pad (3-1);
• and
• (III) building an arch bridge
• erecting, after step (II), an arch bridge (4) by using reinforced concrete, pouring plain concrete at a top of the arch bridge (4) to form a filling layer (4-1), and pouring reinforced concrete on an upper portion of the filling layer (4-1) to serve as a bottom plate (4-3).