Validation of the Vegetation and Soil Shear Tester (VASST) With Existing Soil Strength Instruments.

The U.S. Army is concerned with the most effective and environmentally sustainable use of its military training lands. The understanding of the complex interactions between soil strength and vegetation will prove to be vital in making recommendation for land management of military training lands. One of the objectives of the Optimal Allocation of Land for Training and Non-Training Uses (OPAL) program is to quantify the effects of vegetation on soil stength as it relates to vehicle mobility and trafficability. The Vegetation And Soil Shear Tester (VASST) was designed and constructed to help quantify these effects. Designed to measure the shear force of various configurations of tire analogs over different vegetated soil types, the VASST has been used, along with a set of other soil strength instruments, in field and laboratory tests. This paper will present data comparisons between the VASST and existing soil strength instruments including the: dynamic drop cone penemtrometer (Goodwin, 1991), FieldScout® soil cone penetrometer, Lafayette Instrument® Clegg Impact Soil Tester and the Pilcon® Shear Vane. Comparisons of the VASST data with existing soil strength instrument data will help validate the VASST and determine how it will be used in future studies related to soil strength interactions, sustainable land management practices, and vehicle mobility and trafficability.

Keywords: vegetated soils, soil strength, soil shear strength, vehicle trafficking