Reliability of Pressure Cells to Measure Traffic-Induced Stress in the Topsoil-Subsoil Interface

摘要

Due to increasing wheel loads in agriculture in the last 10-15 years, subsoil compaction becomes a problem ever more. In contrast with the topsoil the subsoil can be loosened with great effort only. To study subsoil compaction induced by vehicle traffic pressure cells are used frequently to measure stresses in the topsoil-subsoil interface. In many cases the results are questionable. First the soil has to be disturbed to implant the pressure cells and they are mostly stiffer than the soil, so stresses are concentrated on the cells. Soil bin experiments have shown that stresses can be measured accurately if the cell is embedded in the hard subsoil with the surface in plane with the topsoil-subsoil interface. The authors tested the reliability of pressure cells in field experiments with two installation methods. In the first method the topsoil was removed over a large width. In this way the pressure cells can be installed with great care and a homogeneous topsoil condition can be created. In the second method the cells were installed by way of horizontally milled holes to prevent topsoil disturbance.