METHOD FOR CONSTRUCTING EXTRA-LARGE VARIABLE CROSS SECTION TUNNEL

摘要

A method for constructing an extra-large variable cross section tunnel. The method comprises: excavating left pilot tunnels (11) and timely constructing primary supports and temporary supports; packing large boot-shaped wall feet (13) and constructing right pilot tunnels (12) by the same process; excavating the upper half part of the left side of a main tunnel (2) and timely constructing first-layer primary supports (23), temporary vertical braces (91) and temporary inverted arches; excavating the lower half part of the left side of the main tunnel (2) and timely constructing the first-layer primary supports (23) and the temporary vertical braces (91); 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 the first-layer primary supports; constructing second-layer primary supports (24) and removing the temporary braces and the temporary inverted arches of the arch part; excavating a central part and timely constructing primary supports (8) of the inverted arches; removing the temporary supports (17) of the left and right lower pilot tunnels, packing the secondary lining of the inverted arches, and filling the bottom of the tunnel; and finally one-time packing the secondary lining (22) of the arch wall by means of a model board trolley. The construction method effectively reduces the safety risk of removing the temporary supports, increases the operation freedom degree and accelerates the construction schedule.