Vegetation and Soil Shear Tester (VASST): A New Method to Measure Soil Shear.

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 the effects of vegetation on soil strength as it relates to mobility and trafficability. The instrument was designed to measure the shear force of various configurations of tire analogs over different vegetated soil types. An overview of the design of the VASST, the development of the field testing procedure, the raw data outputs (force versus distance plots), and the initial data analysis procedure (consisting of shear force versus shear distance plots) will be presented. Quantifying the effects of vegetation on soil strength will prove to be vital in making recommendation for the use of and land treatment of vegetated military training lands.