The treatment of karst features encountered during road construction in County Galway

This paper addresses the identification and treatment of karst features during the construction of the M17/M18 Gort to Tuam motorway. Extensive karstification is known to occur in the limestones of the mid Galway region of... [ view full abstract ]

This paper addresses the identification and treatment of karst features during the construction of the M17/M18 Gort to Tuam motorway. Extensive karstification is known to occur in the limestones of the mid Galway region of Ireland. A karst risk assessment was carried out in advance of the geotechnical design of the earthworks and structural foundations which gave rise to a karst feature identification protocol and a “menu” of prescriptive treatment measures. Several karst features were identified and treated in this manner in a number of locations, however unusually extensive conduit karst features were found to be converging under the central pier of a bridge structure. Linear karst features were also encountered adjacent to this structure. The paper describes how these features were identified and how the surrounding completely weathered rock/clay infilled void was treated using a number of methods, dependent upon its depth, size and impact rating.