Vegetatet support grid embankment systems: current condition, vegetation and suggestions for improvements concerning the choice of the system and a sustained vegetation (VSS2009/601)
Overview
Background & policy context:
Vegetated support grid embankment systems (inclination up to 70°C) are used at road construction especially for noise protection constructions. However increasing manifestations are found, that the planted vegetation is not sustainable. It is assumed, that a marginal rain yield factor, the poor moisture penetration of the wall face, the hindering of plant growth by geosynthetics and a difficult rejuvenation of the plants are the basic causes. Therefore the aim of the project is to survey and to analyze the current condition of existing support grid embankment systems. After the choice of suitable objects regarding age, location and exposition the following factors shall be examined:
- Location (local climate, pH, water-holding capacity, the course of moisturization)
- Vegetation (species, ratio, origin, salt tolerance, pests)
- Reinforcement (corrosion, connection points, emplacement, current condition of the geosynthetics).
Based upon this, it is meant to develop decision guidances, so that the local conditions (aridity, salt contaminated spray, pests etc.) can be taken in better consideration when to choose a noise protection system and sustainable solutions can be found. The analysis of the results will also allow to improve the seed mixtures for the wet sowing at locations influenced by such extreme conditions and to optimize the catalogue of groves for the vegetation.
Objectives:
The project has following objectives:
1) To provide a survey of the current condition of vegetated support grid embankment systems of different age and in different location
2) To provide a typification of the investigated objects concerning the typical location features, typical vegetation features, current condition of the reinforcement
3) To develop a decision guidance, when to use support grid embankment systems, when to use noise protection walls with green facing, when to vegetate with groves, when to vegetate with herbs, when sowing of dry turf
4) To optimize the substratum and cultivation (improving the seed mixtures, improving the list of suitable groves with regard to sustained vegetation.
Methodology:
Following steps will be done during the project activities:
- Screening selection 1: Research
- Investigation selection 2: Location during two growing seasons
- Evaluating climate data of the nearest SMA stations
- Determination of water content (vol.%) Of the soil substrate by taking soil core samples and analysis in the laboratory
- Removal of mixed samples and laboratory analyzes. Microstructure, grain size, pH, nutrients content N, P, K and road salt content
- Investigation selection 2: Vegetation during two growing seasons
- Determination of vegetation coverage means standardized image analysis
- Evaluating the types of the population biology
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