As a method for constructing a tunnel, what is termed the sealed construction, wherein a tubular wall is constructed by assembling segments (mainly made of concrete or steel) on the inner surface of an excavated tunnel is well known.
As segments used in this sealed construction, a rectangular arc shaped plate in planar view is the most common type, and each of these segments are joined together with bolts.
In the most common structure for joining the segments together with bolts, when abutting the joining surfaces of the segments with each other, coupler plates having holes communicating with each other are buried in the neighborhood of the joint surface of the segments, bolts are inserted into the holes of the coupler plates, the bolts are fastened with nuts, and the segments are joined. In addition, there are also structures wherein an metal insertion fittings are buried in the segments, and both are joined together by fastening the bolt member which runs through the adjacent segments.
However, in the above-described structures, at the construction site, the complicated operations of inserting the bolts into the holes formed on the joining surface of the coupler and fastening the bolts to the nuts, and fastening the bolts to the metal insertion fitting buried in each of the segments are necessary, and thus there are limits to reducing the assembly time. In addition, this is difficult to apply automatic assembly by robots. Furthermore, even if the secondary covering construction is omitted, because bolts and nuts are installed, it is necessary to carry out the closing operation of the bolt boxes formed on the segments. In aiming to speed up the operation and make it more energy efficient, in the present state, the development of a new coupler structure is a pressing need.
Therefore, it is an object of the present invention to provide segments which can be joined together very easily and securely.