It was recognised by Lincolnshire County Council that an increasing number of roads on their network have been subject to apparent drought-related subsidence during the last several years. UK Government has highlighted extreme climatic events as a high risk to highway infrastructure assets.
There are many types of soil related ground movement that could have exerted an impact on the highway infrastructure of Lincolnshire, all of which are influenced by climatic processes, including: 1) clay shrinkage and swelling; 2) sand-washout; 3) frost heave; 4) compression of soft soils; and 5) peat shrinkage.
Making use of a range of road condition survey data provided by Lincolnshire County Council and Cranfield University National Soil Resources Institute’s Natural Perils Directory (NPD) geohazard thematic dataset, the relationship between soil type and road degradation has been investigated and further understood. A Geographical Information System (GIS) was used to capture, present and analyse the data; the ESRI GIS ArcMap v.10.1 was used for this study.
This rapid assessment has revealed that, although road deterioration is affected by a number of recognised factors such as traffic use, infrastructure service trenches, cold weather, poor construction of roadway etc. the soil type also appears to have had an important impact upon the condition of the highway network. Clay and silt soils have the most contributory effect to road degradation. Subsequently, the low deflection rates observed in ‘at risk’ silt soils possibly indicate that ‘frost heave’ may be responsible for the worsening road conditions in certain areas of the Lincolnshire road network, contrary to the drought related issues initially identified. It was not possible to determine the fully representative effect of peat soils due to the short length of surveyed road network.