What are the tunnel construction methods of mine method?

The mining method tunnel construction methods are: full section excavation method, step construction method, circular excavation and leave the core soil method.

The full section excavation method is according to the design contour of a blast molding, and then build the lining construction method.

Ring-shaped excavation to leave the core soil method should pay attention to the following points:

(1) ring-shaped excavation footage should be 0.5-1.0m, the core soil area should be not less than 50% of the entire section area.

(2) After excavation, spray anchor support should be constructed in time, steel frame support should be installed, adjacent steel frames must be connected with steel bars, and corner locking anchors should be designed and constructed according to the construction requirements.

(3) When the surrounding rock is in poor geological conditions and the self-stabilization time is short, over-support should be carried out according to the design requirements before excavation.

(4) The core soil and the lower step excavation should then be completed after the upper step support, shotcrete to reach 70% of the design strength.

Step excavation

(1) solve the problem of mutual interference between the upper and lower half section operations. Micro-steps are basically combined into a working face for synchronous excavation; long steps are basically pulled apart, less interference; and short steps are more interference, pay attention to the organization of the operation. For the shorter length of the tunnel, the upper half section through, and then the lower half section construction.

(2) When excavating the lower part, attention should be paid to the stability of the upper part. If the stability of the surrounding rock is better, then it can be excavated in sequence in sections; if the stability of the surrounding rock is poor, then the lower part of the excavation cycle should be shortened; if the stability is even worse, then it can be staggered left and right, or pulling the middle groove first and then digging the side gangs.

(3) The lower side wall must be sprayed with concrete immediately after excavation, and do the initial support according to regulations.