Acid Sulfate Rock Management In Earthworks For Roads

Acid sulfate rocks (ASR) have elevated levels of reduced sulfur, usually as pyrite or other sulfide minerals, and in NSW occur in the lower Sydney Basin and other areas. When exposed to water and oxygen a series of chemical reactions lead to the formation of acid leachates and sulfate salts, and the acidic conditions can also produce high levels of metals in solution. These products can be damaging to both the environment and engineering elements of roads such as concrete and steel bridge foundations and culverts, geotechnical reinforcements such as reinforced soil wall straps and rockbolts, cut batters and pavement materials. This paper presents experiences with ASR in road projects including an overview of the basic science, investigation and test methods, ASR characterisation, design considerations, management plans and construction issues. The Conjola Mountain realignment project on the Princes Highway in southern NSW is presented as a case study together with some research work undertaken on this project.