Construction method for super-large section and transition section of road tunnel bifurcation

Abstract

The invention discloses a construction method for a super-large section and a transition section of a road tunnel bifurcation, and belongs to the technical field of tunnel engineering. The construction method comprises the steps that 1) excavation is conducted from the end of a bifurcation way on the right side of a tunnel to the transition section, and an upper right pilot tunnel is excavated in a large section; 2) temporary support is conducted on the upper right pilot tunnel excavated in the step 1); 3) the transition section of the tunnel is excavated forwards horizontally from an upper step of the upper right pilot tunnel of the large section, and an upper step of a pilot tunnel on the right side of the transition section is formed after a certain distance is excavated; and 4) primary support is conducted on the upper right pilot tunnel excavated in the step 3), and meanwhile locking opening reinforcing and the like are conducted. According to the construction method for the super-large section and the transition section of the road tunnel bifurcation, the pilot tunnel is adopted to penetrate through the super-large section in advance, and support of the head section and the tail section of the super-large section is strengthened; through the special excavation method and the support mode, the safety of the excavation process can be ensured, and the situations of excessive vault settlement, arch wall convergence, unstable arch springing, serious heaving floor and the like caused by the fact that the section is too large can be avoided; and compared with an existing excavation method, the construction method has the advantages that the number of temporary supports is small, and support dismounting is easier.

Description

technical field [0001] The invention relates to the technical field of tunnel engineering, in particular to a construction method for a super-large section and a gradual transition section of a bifurcation part of a hard surrounding rock tunnel. Background technique [0002] When the excavation section in underground engineering (including tunnel engineering) is large, it is called a large section. In construction engineering, the force of large section excavation is relatively unfavorable. The International Tunnel Association defines a super-large cross-section with a clear cross-sectional area / ㎡ greater than 100. [0003] In the construction process of tunnels with super-large cross-section and hard surrounding rock, the traditional excavation methods are double-side-wall pilot-pit method, CD method, CRD method, etc. For the intersection of two small-section tunnels to form a super-large-section tunnel, and then to a gradual tunnel with a gradually smaller cross-section, ...

AI Technical Summary

Problems solved by technology

[0004] In view of this, the purpose of the present invention is to provide a construction method for the super-large section and the gradual change section of the bifurcation part of the highway tunnel, so as to solve the problem that there are many temporary supports in the super-large section and the gradual change section of the tunnel bifurcation section excavated in the prior art, and the support needs to be disassembled. Difficult, large span, large free space, high construction risk and other technical problems

Images