U.S. Department of Defense


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This report describes a preliminary study in support of ongoing research to model soil stress resulting from vehicular traffic on unprepared ground. The soils used in this study were sand, wet sand, and silt. The soils in the prepared soil beds were first characterized as to strength, density, and plasticity. Then pressure sensors were embedded at depths of 2 and 5 in. These were then traversed several times by a Mine Detonation Trailer (MDT) and the pressure produced by a single chosen wheel re-corded. The actual measured load of this wheel was 4700 pounds. The same series of measurements were made using the CRREL Instrumented Vehicle (CIV) with a measured wheel load of about 1500 pounds. The results were compared with the expected values calculated using the Froehlich modification of the Boussinesq equation. For the MDT the correspondence was very good for the sand tests, and acceptable for silt. However, for the CIV the correspondence was unsatisfactory, underpredicting by a significant amount. The Federal Aviation Administration’s Layered Elastic Analysis (LEAF) program was also applied to the MDT case and yielded results similar to the MDT Boussinesq analysis. Possible causes for the observed discrepancies are suggested.