Heave of a building induced by swelling of an anhydritic Triassic claystone

Abstract

This paper describes the conditions leading to a sustained, low-rate, heave phenomenon affecting a building founded on hard Keuper anhydritic rock. The building was located in an abandoned gypsum quarry. Monitoring data as well as vertical profiles of gypsum and anhydrite content indicate that swelling was associated with the presence of a shallow level of anhydritic clay rock. This paper concludes that the initial quarry excavation as well as the additional building foundation work modified the original stress state and contributed to opening fractures at depth. It also resulted in a facilitated access of water to the upper rock levels, immediately under the foundation footings. Measured heave rates are substantially lower than other rates recorded in a few recent cases. An explanation is provided for the difference. This paper describes a comforting solution for the building.