The use of geotextiles with the tasks arming and protect gaining in importance. In Switzerland there are so far no working instruments for the requirements for appropriate geotextiles. The internationally available documents on the functions arming and protecting are unsatisfactory because they do not include clear procedures yet clear minimum requirements. In particular, missing basics in order to predict the long term behavior of geotextiles with armouring and protection task.
The aim of the project is to provide a basis for predicting the serviceability and long-term behavior of geo-synthetics with the functions reinforcing and protecting.
The main research results were evaluated and compared with its own findings. Existing recommendations, standards and standard proposals were compared. Extensive field and laboratory tests were used to determine the minimum requirements for geo-synthetics with reinforcement task.
35 different geotextiles and geo-grids were procured. To determine the mounting stress tests were mounting in scale 1: 1 carried out with fine-grained sand and mixed-grained soils of round and crushed gravel. The compression was carried out under the usual conditions for reinforced structures. Particle size distribution and geometry of the components of the soil material have a significant influence on the damage to individual geo types of plastics. The resistance of a geo-synthetic against mounting stress depends primarily on the type of manufacture and only secondarily on the polymeric raw material. Both the nature of the tension elements as well as the structure of the sheet-like structure has a strong influence on the robustness. The course of the stress-strain curve is not changed by a relevant mounting stress in most cases, ie. the modulus of elasticity remains the same even with a decrease of tensile strength and elongation at break in about. A laboratory test to determine the effect of installation damage has been established and validated. For individual test setups a useful correlation between laboratory and field trial was found.
With minimum requirements for the resistance to installation damage, which are supported on the presented laboratory-installation simulation, it is in most cases on the safe side. With selected geo-synthetics creep and creep tests were carried out on narrow grid and fabric strips under various temperatures. These primarily served to assess the suitability of measures proposed in the literature lapse experiments to economical calculation of creep and creep behavior of geo-synthetics. It was found that creep are promising only with long test times and optimally adapted clamping systems, and that the significance of time-lapse creep must be scrutinized under elevated temperatures.
Several months outdoor exposure served to estimate the influence of installation delays, is in which the geo-synthetic covered immediately after laying. The investigations showed that the weather resistance in addition to the polymer raw material is highly dependent on the added UV stabilizers.
The weathering was carried out also on samples under tension to simulate, for example, the stress of geo-synthetics during installation into end faces of reinforced steep slopes. It was found that the applied voltage, although in some cases, accelerated aging, a correlation to the stress-free state but is not present.
Based on the findings from our own research and from the liter