Laboratory foundation model with pyrite-bearing mudstone fill

Damage to domestic dwellings in the greater Dublin area of Ireland engendered by the expansion of the underfloor fill material containing pyrite has become a high-profile national problem in recent years. In this paper, a novel physical model is described in which the profile of underfloor materials representative of Irish construction practice is modelled; the relevant vertical dimensions are at full scale. The study has enabled the rate of pyritiferous expansion to be ascertained over a period of 830 d at laboratory temperatures; rates of 0.0021 and 0.0008 (mm/mm)/year were observed with no loading and a pressure of 3.4 kPa on the concrete slab, respectively. The rates of expansion are broadly consistent with those obtained from reference pipe experiments. These data are an important frame of reference for anticipating the time required to generate a specific amount of floor movement in domestic dwellings. Pressures generated within the fill are low and consistent with the occurrence of significant expansion.