Infra-red thermographic inspection of trackbed ballast

Railway trackbed is inspected regularly, in order to detect possible degradation of the ballast and subgrade. At the present time investigation of the tracks is undertaken by a combination of visual inspection backed up by selective trial pitting at intervals along the track. Continuous information on the ballast suitability cannot be obtained by this method. Infra-red thermography is a possible means of determining the condition of the track bed. The technique is very cost effective and large surveys can be undertaken rapidly. It is also non-intrusive and causes no environmental impact. A theoretical analysis was undertaken which showed that it is possible to use infra-red thermography to discriminate between clean and spent ballast. Initial results from a full scale field trial showed that the theoretical work can be transferred to a full-scale railway trackbed ballast. For the covering abstract see ITRD E125214.