Method for constructing extra-large variable cross section tunnel

Abstract

The invention discloses a method for constructing an extra-large variable cross section tunnel. The method comprises the following steps: firstly excavating left pilot tunnels and timely constructing primary supports and temporary supports; packing large boot-shaped wall feet and constructing right pilot tunnels by the same process; excavating the upper half part of the left side of the main tunnel and timely constructing first-layer primary supports, temporary vertical braces and temporary inverted arches; excavating the lower half part and timely constructing first-layer primary supports and temporary vertical braces; constructing the upper half part of the right side of the main tunnel by the same process and excavating a middle arch part and timely constructing first-layer primary supports; constructing second-layer primary supports and removing the temporary braces and temporary inverted arches of the arch part; excavating a central part and timely constructing the primary supports of the inverted arches; removing the temporary supports of the left and right lower pilot tunnels, packing the secondary lining of the inverted arch, and filling the bottom of the tunnel; finally once packing the secondary lining of the arch wall by a model board trolley. According to the method, the safety risk for removing the temporary supports can be effectively reduced, the operation freedom degree is increased and the construction schedule is quickened.

Description

technical field [0001] The invention relates to the field of tunnel construction in weak surrounding rocks, in particular to a construction method for super-large variable-section tunnels. Background technique [0002] With the development of tunnel engineering construction, the deepening of construction technology research and the continuous updating of mechanical equipment, the construction methods of super large cross-section tunnels have made great progress. At present, the specific methods of traffic tunnel excavation mainly include: full-section method, step method, step division method, middle partition method (CD method), cross middle partition method (CRD method) and side wall pilot pit method, etc. However, in engineering practice, it is very difficult to construct super-long-span tunnels with a span of 20-30m in weak surrounding rock. The construction safety of the first three methods cannot be guaranteed, and the deformation of the surrounding rock is uncontrolla...

AI Technical Summary

Problems solved by technology

However, in engineering practice, it is very difficult to construct super-long-span tunnels with a span of 20-30m in weak surrounding rock. The construction safety of the first three methods cannot be guaranteed, and the deformation of the surrounding rock is uncontrollable and prone to landslides; the latter three methods There are many temporary supports, which are uneconomical and inconvenient for construction operations, reducing the degree of freedom of construction. The removal of temporary supports may cause the risk of force system conversion, resulting in a limited distance for one-time removal of supports, and the progress of the construction period will not be guaranteed.

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