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Title: Comparison of thawing soil strength measurements for predicting vehicle performance
Authors: Shoop, Sally A. (Sally Annette)
Keywords: Freeze/thaw
Thaw depth
Traction prediction comparison
Unsaturated soil
Vehicle mobility
Shear strength
Water moisture content
Soil strength
Soil mechanics
Publisher: Cold Regions Research and Engineering Laboratory (U.S.)
Engineer Research and Development Center (U.S.)
Series/Report no.: CRREL report ; 92-17.
Description: CRREL Report
Abstract: The CRREL Instrumented Vehicle (CIV), shear annulus, direct shear, and triaxial compression devices were used to characterize the strength of thawed and thawing soil. These strength values can be used in simple traction models to predict the tractive performance of vehicles. Strength was evaluated in terms of the parameters c' and ɸ based on the Mohr-Coulomb failure criterion. It is proposed here that an instrumented vehicle is best suited for terrain characterization for mobility studies because the conditions created by a tire slipping on a soil surface are exactly duplicated. The c' and ɸ' values from the shear annulus were were found to overpredict traction because of the low normal stress applied by the annulus and the curved nature of the failure envelope. Of all the tests, the direct shear test yielded the highest nature of the failure envelope. Of all the tests, the direct shear test yielded the highest ɸ' value, most likely because the test was run at a slow deformation rate under drained conditions. The triaxial test results were the most similar to those from the vehicle. All test methods show ɸ' increasing with soil moisture up to the liquid limit of the soil and then decreasing. As measured with the vehicle, ɸ' was also found to be strongly influenced by the thaw depth.
Rights: Approved for public release; distribution is unlimited.
Appears in Collections:CRREL Report

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