Tunnel construction is a complex project, in which inverted arch and floor construction are important links. This paper will introduce the matters needing attention in the construction of inverted arch and bottom plate, so as to help the constructors finish their work better.

♂? Advance construction

Inverted arch concrete should be constructed before arch wall concrete, and the lining cycle length should be kept at least 3 times. Floor concrete can be poured in half, but the joints should be smooth and waterproof.

Overexcavation backfill

Overexcavation of tunnel bottom (including inverted arch) is within the allowable range, and concrete with the same strength grade as lining should be used for pouring. When the overbreak exceeds the specified amount, it should be backfilled according to the design requirements, avoiding backfilling with cave slag at will, and it is forbidden for flaky to invade the lining section (or inverted arch section).

construction sequence

Concrete above the inverted arch or flaky concrete can only be constructed after the inverted arch concrete reaches 70% of the design strength. The concrete strength of inverted arch and bottom slab should reach 100% of the design strength before it can pass.