Federal Highway Research Institute


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Sustainability, Resource Protection and Earthwork Materials in Road Construction

Testing and optimisation of a resilience management concept - case study-based investigations for the transport modes road, rail and waterway in the context of climate change (69.0010)
The aim of this research project of thematic field 1 "Climate change impacts and adaptation" of the BMVI expert network is the testing and optimisation of a resilience management concept, which was developed for the federal trunk road network and is to be tested and conceptually and methodologically refined for the transport modes road, rail and waterway on the basis of case studies in the context of climate change. In 3 case studies, concrete application cases of resilience management will be played out in the sense of a simulation game in order to test the practical suitability of the resilience management concept against the background of current planning practice, the data situation and its objectives and sub-steps, among other things. In the process, heat events, river floods and heavy rainfall/ flash floods (case study 1), storm events (case study 2) and critical management situations (case study 3) are considered.

Criticality analysis for federal transport routes as a component of the climate impact analysis (69.0003)
The aim of the project is to understand, document and quantitatively process the interrelationships of transport modes in the context of intermodal transport. The background to this is the fact that the modes of transport are interlinked in many cases in the supply chain as well as in passenger transport. For example, goods are delivered to a seaport, transported further by train and brought to their final destination from the station by truck. The related assumption is that the criticality assessment in one mode of transport is not independent of the other modes. The extent of these linkages and their mutual influence on mode-specific criticality will be investigated in more detail in this project.

Assessment of the stability of potentially landslide-prone slopes and embankments along the federal trunk road network (05.0208)
Gravitational mass movements can already affect traffic and transport infrastructure in various ways. In a completed research project, an engineering-geological model approach to gravitational mass movements was developed for the federal trunk road network. The generalised approach primarily serves to provide a nationwide overview with regard to exposed stretches of road. Detailed studies in focus areas would make it possible to validate the existing model results and thus to further specify the hazard assessment. The aim of the project is to assess the stability of potentially unstable slopes and embankments along selected stretches of the federal trunk road network. In addition, it is planned to develop impact scenarios related to climatic influences for the selected focus areas. A case study is to be prepared for each selected road section.

Identification of relevant climate parameters and determination of threshold values for gravitational mass movements in Germany, including preparation of a validation concept (01.0202)
Gravitational mass movements can already affect traffic and transport infrastructure in various ways. Within the framework of the first phase of the BMVI Network of Experts (2016-2019), a climate impact analysis was developed in Theme 1 "Adapting transport and infrastructure to climate change and extreme weather events", which provides a methodological framework for analysing the impact of climate change and extreme weather events on transport infrastructure. The aim of the present research project is to review the previous selection of climate parameters and to determine valid threshold values that could lead to the triggering of gravitational mass movements. In order to be able to make a statement on the influence of climate change in connection with mass movements, fundamental mechanisms of action between the basic disposition and the influence of the climate or weather must be investigated and understood – for example, the duration and intensity of precipitation or temperature changes such as freeze-thaw cycles.

Local Analysis and Mapping of Potential Flood Areas in the Federal Highway Network of North Rhine-Westphalia as a Result of Heavy Rain Events (Blue Spot Analysis) (01.1200)
Initial investigations by the German Weather Service have shown that small-scale heavy rainfall events have become more frequent in Germany in recent years. These changes in precipitation conditions can locally lead to an increase in the risk potential of flooding caused by heavy rainfall events, especially in topographic sinks. A blue spot model in the form of a toolbox in a geographic information system (GIS) is to be developed for North Rhine-Westphalia (NRW) as an example for the hazard assessment and assessment of potential flooding in the area of the federal trunk road network due to local heavy rain events. A blue spot analysis for NRW is to be carried out and an overview map is to be produced. In addition, a systematic evaluation of the model and the results will be carried out on the basis of an investigation concept to be developed for network-wide model evaluation. The findings are incorporated into the work of the BASt within the BMVI expert network.

Examination of the superimposed federal state flood hazard maps over the federal trunk road network based on remote sensing data and archive information (3317000)
The federal states in Germany have among other things prepared flood hazard maps against the background of transposing the European Floods Directive into German law. Based on the data provided by the federal states, BASt has superimposed the flood hazard maps over the federal trunk road network in a geographic information system (GIS) to obtain information about especially vulnerable areas of the federal trunk road network. This research project focuses on the question of the extent to which the superimposing of the flood hazard maps over the federal trunk road network is suitable for use as a national foundation for a risk analysis of the federal trunk road network. This assessment is initially to be based on an empirical approach. During the research project there will be a spatial comparison of the vulnerable areas indicated by the superimposing exercise with areas that have actually flooded during past flood incidents. Remote sensing data and archive data will be used for the comparison.

Heat indicator climate impact analysis (3317001)
The RIVA tool is to be further developed into a comprehensive climate impact analysis tool for the road traffic system. Indicators for climate impact analysis are to be defined accordingly for the external impact parameters, including climate and extreme weather events. Within the course of the project, an indicator for estimating damage to asphalt pavements caused by heat is to be developed as an input variable for the climate impact analysis. This indicator enables the existing RIVA method to be further developed into a climate impact analysis tool. The climate impact analysis tool can provide road construction planners with information to assess the impact of climate-related influences of the road traffic infrastructure.

Network of experts: climate change (3316002)
The project addresses the following questions amongst others. Which climatic changes are relevant to traffic and infrastructure in Germany? Which climate scenarios do we need to consider? How vulnerable are traffic and infrastructure to climatic changes and extreme weather events? Which sections in the transport network could be weak points? Which options, measures and procedures are available to safeguard and enhance resilience in the entire transport system? How do the combined effects of climate change and other anthropogenic changes impact traffic and infrastructure? What does this mean for the maintenance, planning and construction of infrastructures? How can we make reliable climate forecasts for planning periods of 10 to 30 years alongside long-term climate projections and use them in the planning instruments and in the maintenance and renewal of the transport network?

Modelling of Temperature Gradients in Concrete Road Constructions (3312002)
Climate researchers are anticipating considerable climate changed in the coming decades. The German Meteorological Office continuously records meteorological data including the temperatures at ground level, whilst the road construction authorities record road surface temperatures by using ice warning systems. The frost dimensioning was updated in 2008. This means that the surface temperatures and the maximum frost penetration depths which are to be anticipated at federal highways are known. Exact information on how the temperatures are distributed in road constructions is not known for certain at the moment. This is of great relevance for the analysing of the long-term behaviour however. 25 percent of the German federal highways have concrete surfaces. An influence model is to be developed in the scope of the project which can be used to calculate the temperature gradients on the basis of data from weather stations, construction and material identifiers in addition to all of the relevant information concerning the environment. This influence model is validated with the results of a German-wide temperature monitoring on concrete road constructions. This results in a backed-up influence model which will supply important input data for the dimensioning of the concrete construction designs. On the basis of this, the model provides the possibility of computing the temperature gradients on the basis of the most diverse climate scenarios.

Influence of temporarily occurring groundwater on the stability of road cut slopes (05.0195)
Unexpected landslides or slope failures lead to construction stoppages and considerable additional costs. Such damage scenarios are not uncommon and are often caused by temporary water-bearing layers that were not or could not be detected during the exploration. Within the framework of the research project, the influence of water, especially of temporarily occurring groundwater and strata water, on slopes will be systematically investigated and evaluated. As a result, a concept is to be developed by which means the presence of temporarily occurring groundwater or strata water can already be detected during the subsoil investigation and can then be observed in the further course of time. Furthermore, it is to be investigated how the influence of temporarily occurring groundwater should be considered in stability calculations or whether additional processes and failure mechanisms should be considered. The results should be included in the revision of the instruction sheet on geotechnical investigations and design in traffic route engineering (M GUB).

Review of the effects of the application of the filter rules for geosynthetics of M Geok E (05.0198)
The filter rules for geosynthetics are differentiated by classifying the application into 3 safety cases and by specifying ranges of the permissible effective opening width. During the work at that time, the upper limit was considered technically reasonable and worth striving for, while the lower limit was also a concession to the available products. In the meantime, practically only products with opening widths at the lower limit are available on the market. There are increasing reports that this product use leads to a reduction in permeability until the products become blocked in contact with the soil. In addition to undesired wetting, problems relevant to stability can also be expected. This will result in a failure of the hydraulic filter efficiency. There is no reliable overview of geotextile filter applications and experiences. The aim of the project is to investigate to what extent the filter rules used still correspond to the state of the art, to what extent the lower limits of the opening width represent a risk and to what extent geosynthetics can be made available for the required area. Furthermore, decision support should show in which cases geosynthetics should rather be avoided.

Review of geotextile robustness classes with regard to new product developments (05.0199)
The geotextile robustness classes of the M Geok E were developed and defined in the 1990s on the basis of investigations into the installation stress for the products available at that time. In the meantime, strongly modified and newly developed products are on the market, which promise a more economical and effective use and probably do not fit into the present scheme. In addition, the demands on the products have increased, so that the lower classes have been dropped in the meantime. There is no systematic processing of a current product range with the same boundary conditions that would allow a target-oriented classification. Therefore, the aim of the research project is to check the geotextile robustness classes.

Suitability of conventional test methods for recycled construction materials and industrial by-products in earthworks (05.0203)
Conventional test methods are not necessarily suitable for testing some industrial by-products or recycled construction materials in earthworks. For example, the Proctor test often cannot determine a Proctor optimum in the sense of a maximum at a water content. Therefore, this research project aims to investigate the suitability of conventional testing methods for recycled building materials and industrial by-products in order to prove the suitability of the building material for the intended use. For the contractually safe application it is necessary to create regulations by which building materials can be evaluated with regard to their suitability. The use of industrial by-products and recycled building materials in earthworks should continue to be possible if there are no objections to this because of construction and environmental reasons.

Basic principles for the suitability testing of soils with organic components for use as building material in earthworks (05.0204)
Soils with organic additives are currently not or only subordinate used in earthworks due to their generally lower shear strength and greater deformability compared to purely mineral soils. As existing laboratory methods are for the most part not designed for the special properties of organic components in soil, this already appears to be an obstacle to the use of such materials. As a result, test results from different laboratories are often not comparable, which may even lead to contractual disputes. In this research project, the basic principles for the suitability testing of soils with organic components for the purpose of use as earth building material are to be developed. The additional requirements and advice necessary for the meaningful application of existing laboratory methods are to be developed.

Testing and assessment of the durability of temporarily flowable and self-compacting fill materials (ZFSV) in the subgrade of traffic areas (05.0205)
For some years now, ZFSV have been used in Germany for filling (pipeline) trenches and in areas of backfill that are difficult to compact. ZFSV are often prepared from locally available excavated soil by adding water, bentonite and a small amount of binder to form a flowable fill material which, after solidification, should achieve previously defined final properties. To prove suitability, various requirements must be specified according to ZTV E-StB, such as proof of durability. Binding test specifications and criteria for evaluation have been lacking to date. The aim is therefore to develop practical test procedures and suitable criteria for assessing the durability of the ZFSV. The results shall provide a draft of a test specification for the qualification test for the durability of ZFSV as well as evaluation criteria for the incorporation into the ZTV E-StB.

Examination of how lignite fly ash reacts in ground improvement measures (05.0188)
Mixtures made from standardised binding agents (including lime and cement) have been produced for many years and used successfully in ground improvement measures. In addition to mixed binding agents, mixtures with added lignite fly ash (LFA) as well as “pure” LFA are available on the market. LFA is a non-standardised industrial by-product. The objective of the research is to examine the possibilities for using LFA as a binding agent for ground improvement in earthworks. This entails a systematic examination of the effectiveness of LFA with regard to reducing water content in the same way as fine lime and to hydraulic setting in the same way as cement. The research should also establish how the expansion factor is to be examined, and whether there is a need to supplement or revise the rules and regulations (German Engineering Code for Soil and Rock in Road Construction data sheet – TP BF-StB ).