Application of Shrinkage and Swelling Factors on State Highway Construction

Abstract

The objectives of the research were to review the state of practice for roadway related earthwork calculations for the southeastern states, develop a calculation tool for comparing various state earthwork methods, demonstrate and compare earthwork calculations methods used in southeastern state departments of transportation (DOTs), and evaluate shrinkage and swelling factors used in southeastern state DOTs. The southeastern states being observed in this research are Alabama, Florida, Georgia, North Carolina, South Carolina, and Tennessee. First, a background study and literature review was conducted on earthwork calculation methods including shrinkage and swell factors. This study included various southeastern state DOT methods in the United States. Next, an analysis tool was developed. This spreadsheet tool was used for the comparison of earthwork methods and the evaluation of the impact of shrinkage and swell factors. The analysis tool aided in the final aims of the project by using a case study. The state earthwork methods were calculated using the analysis tool which allowed for analysis and comparisons to be made. Finally, from observations of the research and an evaluation of the results of the case study allowed for conclusions to be made based on the findings. The research concluded: (1) The method by which southern states determine earthwork quantities varies from state-state, and can result in a vast difference when compared side-by-side. (2) The differences in earthwork quantities are substantial between southeastern state DOT methods. This was due to whether or not a swell factor is applied to earthwork (some DOTs do not use swell factors) or a result of the shrink factor(s) applied to state earthwork calculations (different DOTs use different factors depending on soil type). (3) The shrinkage and swelling factors have a wide range for soils which are typical in the southeastern United States. From the values in this research, typical ranges for general soil types in the this southeastern region of the United States were found to vary. Shrink percentage ranges from 10-18 % for clays, 11-35 % for sands, 20-25 % for residuals, and 5-22 % for rocky, gravely soils. Swell percentage ranges from 30-50 % for clays, 3-45 % for sands, and 5-40% for rocky, gravely soils. No specific swell percentages were discovered for residual soils in the course of this research. (4) Most southeastern state DOTs do not provide a guide for their typical shrinkage and swelling factors. It appears that earthwork is left at the risk of the contractor. (5) Application of swell percentages was inconsistent among the various DOT earthwork calculation methods. (6) The inclusion and definition of rock (drillable rock or at auger refusal) has a large impact on earthwork calculations using the southeastern DOT earthwork methods.