摘要：The article describes a hazard caused by deformation of a brick vault located under the dungeons of the gate tower of Zamek Górny in Opole at the turn of the 13thand the 14thcenturies, which was used as a school building until 2017. The hazard identified in 2013 was found on the ground level of the building in a communication route of the heavy traffic load. Visual inspections and tests have demonstrated that the existing situation was caused by civil works performed at the dungeon level nearly 6 years earlier due to an unconsidered decision on removing debris and a backfill which filled entirely the lower tower storeys. The above actions resulted in removal of the base of the floor ‘laid on the ground’ in the 19th century [2][4]. In this article, an analysis was carried out to verify possibilities of unbelievable strength of the artificially formed flat vault, which was previously the floor supported on a debris and sand base.
