Analysis of a Fire Riser Failure below a Concrete Slab-on-Grade Foundation

Pressurized water pipes such as fire risers are often installed below commercial building foundations. Hydrostatic pressure imparted on foundation slabs during a fire riser rupture often results in damage to building foundations, requiring a detailed evaluation of the foundation and substrate prior to performing repairs. In isolated cases, the introduction of moisture from a fire riser rupture to underlying expansive soils can initiate volumetric changes that impart additional pressures on the building components. The objective of this paper is to explain the investigative process and methodology used to determine the extent of damage and appropriate repair strategy for these types of failures. A case study is presented to illustrate the investigative methodology, involving a ruptured fire riser beneath a concrete (floating) slab-on-grade foundation in Texas. The investigation revealed that a distinct region of the slab-on-grade foundation was damaged as a result of the fire riser rupture and required replacement.