Review of the causes of the unprecedented collapse of the United Grain Growers elevator in Thunder Bay, Ontario

Abstract

This is a case history of the unprecedented collapse of a pile-supported grain elevator which collapsed suddenly into the harbour in Thunder Bay, Ontario on September 23rd.,1959 after a service life without incident for over 30 years. Many similar grain elevators had been built and operated successfully in the area beginning in the 1880’s. Studies directed at establishing the possible cause(s) included: geotechnical investigations, interrogation of background on design, construction, operation and performance, and a forensic evaluation of evidence revealed during removal of the debris in preparation for reconstruction. The site soil conditions together with features of the collapse are described. The elevator had experienced only minor lateral movements which was in marked contrast to other pile-supported elevators in similar ground conditions nearby. This evidence was considered of particular significance. The collapse is attributed to several factors: the failure of the batter piles, followed by that of vertical piles; to the repairs of the revetment and the associated filling of voids, probably aggravated by a ship collision 6 days before the collapse.