Measuring Techniques for the Assessment of the Trafficability of Fen Grasslands

Abstract

Fen grasslands belong to the vertically layered soils with a strong and very variable top layer, the gras sod, on a weak soil base, the peat. Mea- suring techniques for trafficability assessment must reflect the site- specific load-bearing capacity of the ground with sufficient accuracy and show a close relation to permissible mechanical load-input by machine- ry. Furthermore, they must be applicable with tolerable expenditure. In this paper, examinations with a penetrometer, a plate test device, and a shear vane are presented. The cone index only allows for insufficient estimation of the impact of vegetation on the load-bearing capacity. The- re is only a very loose correlation between the values of mechanical load-input by vehicle variants and the necessary cone index. On fen grassland, the load-penetration curves obtained with a plate test device exhibit a typical course with a more or less distinct pressure maximum. Its correlations to soil moisture content and vegetation in principle allow this measuring technique to be used for the assessment of the load- bearing capacity. This also applies to the prediction of the permissible load-input during the passage of vehicles. However, since a large amount of data is necessary, the expenditures required for plate tests are too high. The shearing vane enables the load-bearing capacity of the the ground and the permissible load-input to be established with sufficient precision. It is therefore an appropriate measuring technique for the as- sessment of the trafficability of fen grasslands on the basis of empirical relations.