Yieldable joint

A yieldable joint between one pair in combination with a plurality of joined pairs of adjacent arcuate plates forming an arcuate structure surrounded by soil such that the adjacent lapped edges of the arcuate plates will shift relative to each other, comprising a pair of arcuate plates to be joined by lapping adjacent edges thereof, at least one pair of corresponding perforations in said lapped plate edges, and a bolt passing radially through each of said pairs of corresponding perforations, at least one perforation of each pair of corresponding perforations comprising a keyhole elongated in the direction along the line of relative movement of said pair of plates, one end of each said keyhole being of such size as to freely receive the shank of said bolt and the remaining elongated portion thereof being of a width less than the diameter of the shank of said bolt, whereby said elongated perforations will permit relative movement of said plates only upon deformation and widening of said remaining elongated portions, the shape of said remaining elongated portions determining the force required for said relative movement of said plates, whereby said underground structure may be designed to carry a substantial and predetermined overfill before any controlled circumferential yielding occurs, and whereby said plates provide a practical slotted type bolted joint for field assembled structures because they may be readily positioned as desired in relation to each other.