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John Rushing, Lulu Edwards, Haley Bell, and Margarita Ordaz
Rapid assessment of low volume road surfaces remains a challenge when attempting to forecast allowable vehicle crossings. Variations in moisture content of the soil can greatly affect trafficability, and predictive equations for soil deformation under vehicle loads often have reduced reliability for low-strength materials. Portable tools to characterize soil stiffness and corresponding relationships to load-induced deformation are needed. In this effort, researchers performed comparative testing of multiple rapid assessment tools as potential devices for giving estimations of vehicle trafficability. The test devices included a Clegg hammer and lightweight deflectometer as instruments that measure response from impulse loading. A dynamic cone penetrometer was used as a basis for comparison. Silty sand with and without chemical stabilizers at varying moisture content were used for testing. These soil conditions represented very weak conditions capable of supporting fewer than 50 vehicle passes to moderate strength conditions capable of supporting several thousand vehicle passes. Data from full-scale tests were used to correlate allowable traffic with data obtained from the rapid assessment tools. Recommendations from the effort include ranges of response data to categorize low-volume road surfaces based on their ability to handle ranges of vehicle loadings.
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