Widening processing structure of prefabricated channel steel of prefabricated erected simply-supported beam between tunnels and construction method thereof

The invention relates to a widening processing structure of a prefabricated channel steel of a prefabricated erected simply-supported beam between tunnels and a construction method thereof. For a bridge between tunnels, if the width of a prefabricated box beam can not meet a transport erection requirement of going through a tunnel by a transporting girder vehicle or a transporting and erecting integration machine, a cast-in-place scheme is employed; however, because of frequent traffic congestion in tunnels and long distance, materials and construction machines can not be transported at a right place easily; and the cast-in-place construction period is long, the whole-line construction period can not controlled easily. According to the invention, a prefabricated channel steel component is arranged at an outer side of an end surface of a prefabricated box girder flange; and the prefabricated channel steel component has a channel steel structure, the notch faces outwardly, and the bottom is fixed at the prefabricated box girder by pre-buried bolts buried in the end surface of the prefabricated box girder flange in advance. Therefore, when the prefabricated beam width can not meet tunnel clear width and clearance requirements, tunnel passing time is less than the prefabricated beam width at the early stage and then the small part is complemented according to the designed beam width after post-stage erection completion. For bridges in tunnels, the field construction procedures can be simplified substantially and the construction period can be shortened effectively; and obvious economic benefits can be created.