Underground interchange bifurcate tunnel underground excavation structure

The invention relates to an underground interchange bifurcate tunnel underground excavation structure which comprises at least one grade of transition segment with the section width gradually increased, a large-span tunnel maximum-section segment connected with the last grade of transition segment, a multi-arch tunnel segment, a small-distance tunnel segment and a separated tunnel segment. A reserved middle rock pillar bifurcating a tunnel is arranged between the small-distance tunnel segment and the separated tunnel segment. A middle partition bifurcating the tunnel is arranged in the middle of the multi-arch tunnel segment. One end of the bifurcated small-distance tunnel segment is connected with the multi-arch tunnel segment. One end of the bifurcated multi-arc tunnel segment is connected with the large-span tunnel maximum-section segment. The bifurcated separated tunnel segment is connected with the other end of the small-distance tunnel segment correspondingly. Compared with the prior art, according to t