Das Projekt "Auswertung und Prognose der mechanischen Auswirkungen auf den Untergrund bei der Verlegung von Gasleitungen in landwirtschaftlichen Boeden" wird vom Umweltbundesamt gefördert und von Eidgenössische Technische Hochschule Zürich, Institut für Terrestrische Ökologie, Fachbereich Bodenschutz durchgeführt. Heavy machinery used for the construction or transport gas pipelines can cause severe and persistent subsoil compaction of agricultural land, depending on various factors among which soil wetness plays a key role. In this project, several field experiments were carried out to investigate the stress propagation under heavy construction machines (40 t and more) during operation on selected plot areas under controlled moisture conditions, to assess the resulting mechanical deformation of the subsoil and to investigate changes of soil properties in particular infiltration patterns of a dye tracer analyzed by computer image analysis. In the laboratory , oedometric compressibility and other properties, in particular bulk density and coarse porosity, of soil samples taken before and after the impact by the machines were determined and compared to measurements of control samples. Furthermore, we investigated the moisture-dependence of the precompression stress by a series of oedometer tests and also performed some shear tests for the purpose of model parameter estimation. Using only a priori parameter values determined from such independent soil tests or just best estimates, the critical-state soil-mechanical model CRISP was used to interpret the results. As far as field observations were available they agreed well with the model simulations. The results lend support to the hypothesis that preconsolidation stress provides a suitable criterion to protect soils against overloading. However, the moisture-dependence of this parameter needs to be better known. Given that homogeneity of the experimental field sites had been a prime criterion of selection, spatial variability between trafficked and untrafficked test plots was still surprisingly large and limiting the detectability of compaction effects more than anticipated.
Das Projekt "Bewertung verschiedener mobiler Abdeckungssysteme fuer den Schutz landwirtschaftlicher Boeden unter Zufahrten vor mecchanischer Schaedigung durch schwere Baufahrzeuge" wird vom Umweltbundesamt gefördert und von Eidgenössische Technische Hochschule Zürich, Institut für Terrestrische Ökologie, Fachbereich Bodenschutz durchgeführt. Construction of pipelines, roads and railway lines often requires the temporary use of fertile soil as access way for very heavy machinery, bearing the risk of adverse effects by compaction of these soils. various mobile covering systems have been. Based on field observations, literature information, personal communications and numerical simulations of a simple scenario, we compared various access way systems proposed to shield the soil below against mechanical damages. Criteria included effectiveness, practical suitability, ecological impacts and cost-efficiency.