The identification of pyrite induced foundation heave by chemical and structural assessments

摘要

The oxidation of pyrite and associated minerals found in mudrocks is a relatively common problem that is encountered in ground engineering. The mechanism behind the reaction is well known, although the consequences of the oxidation can manifest in numerous ways including the accelerated deterioration of construction materials, the production of acidic ground waters or the precipitation of expansive secondary minerals. Problems caused by both oxidation of pyrite and the associated precipitation of secondary minerals are known to have occurred and be occurring in numerous locations worldwide. Damage caused to structures by the oxidation of pyrite-rich rocks can vary depending upon several factors, including the type of structure, the chemistry of the source rock, the environmental conditions and the way in which the materials can interact with the structure. The paper considers the use of chemical and structural assessment methods to determine that pyritic heave was at fault for a series of case studies, and looks at the new Irish Standard developed for use in identifying new cases of pyritic heave in domestic properties. Further testing of the latter is ongoing to evaluate its use for back-analysis of known pyrite cases and whether this analysis can be used to compare the damage seen with the chemical properties of the fill.