CONSTRUCTION METHOD FOR TIMBERING

PROBLEM TO BE SOLVED: To provide a construction method for timbering conformable to problems of a conventional construction method for timbering having the uncertain element that the degree of overlapping cannot be confirmed, the falling of the natural ground of the overlapping part by the absence of the reinforcing core material in the weakest overlapping part and the imperfect structure of the overlapping part, which depends on the method of forming a hardener layer around a reinforcing core material by insert pipes driven in parallel to each other, because the overlapping range of the boundary overlapping parts of the adjacent columnar hardener layers is determined depending on the penetration of a filler or the jet flow arriving range. SOLUTION: An injecting pipe 3 is inserted in to the middle position S between the insert pipes 1a and 1b driven in parallel to each other, and the injection pipe 3 is retreated while force-feeding a ground hardener thereto in a prescribed depth, whereby columnar hardener layers D having a center in the middle position between the insert pipes and holding the insert pipes at both ends are adjacently successively formed.