PURPOSE: To facilitate the injection of concrete slurry as well as to prevent any leakage of the injection material from occurring by forming a releasive joining part in the specified position of each of upper and lower layer fabrics with joining weft joining an interval among fabric layers, in these upper and lower layer fabrics containing at least a part of the weft where ground weaving weft and temporary joining weft both form a pair of weft units.

CONSTITUTION: An upper layer fabric 1 and a lower layer fabric 1' both are joined together by joining warp 5 and 6 at the specified interval both in length and width with the initial thickness (t). Then, mingling with weft, four releasable joining parts 1a, 1b and 2a, 2b are formed there. At that time, at least in the one side layer 1 or 1', among these releasable joining parts 1a, 1b and 2a, 2b, easily water soluble weft 4 and 4' are used for the joining warp 5 and 6 of the specified releasable joining part and the mingled weft. Next, ground-weave weft 3 and 3' are used for the other part weft. With this constitution, an interval among fabric layers is facilitated and uniformized, separating them at the desired interval, whereby the promotion of layer thickening is thus achievable.