CONSTRUCTION OF SEALED DITCHES ALONG EXISTING ROAD

Introduction - The report, which is being carried out in collaboration with the Swedish Transport Administration, investigates how sealed ditches should be constructed along existing roads to protect water sources. The Swedish Transport Administration needs more knowledge about an economically sustainable method for constructing sealed ditches along existing roads, as current requirements are unexplored, and it is difficult to know what they are based on. The aim of the report is to find out how sealed ditches should be constructed along existing roads from a functional and economic point of view. Method - The study uses a mix of quantitative and qualitative methods to answer the two different questions. The research is carried out through case studies and simulations. Data is collected through document studies and workshops, in collaboration with the Swedish Transport Administration. Information searches have been carried out in primarily Primo to collect relevant background information. During the course of the work, simulation and modeling have been used in programs such as Plaxis LE 2D and PMS Object to analyze road sections and their strength. In parallel with the students' work, a working group at the Swedish Transport Administration has conducted an investigation into circumventing certain requirements when designing sealed ditches in Hultsfred. Results – The results are best shown in the form of images in Chapter 4 Results, where three different sections are reported. The calculations have been carried out based on economy, strength at completion and strength during construction. In order to obtain a real economic comparison, the cost for 100 meters of trench was calculated. According to Plaxis LE 2D, Section 1 has a safety factor of 2.428 at completion and a cost of SEK 835,857 for 100 meters of trench. Section 2 has a safety factor of 2.427 and a cost of SEK 638,767. Section 3 has a safety factor of 2.385 and a cost of SEK 556,036. Analysis – Three sections for sealed trenches have been analyzed. Section 3 is the cheapest but difficult to build in practice due to the risk of damage to the waterproofing layer. Section 1 is technically stable and the section that is fully compliant, however, it is expensive and affects traffic around the road construction. Section 2 is therefore the best solution with a good balance between cost, constructability and function. Discussion – The study shows how dense ditches can be constructed along existing roads using simulations, theory and the Swedish Transport Administration's specialists. AutoCAD and Plaxis provided useful results, but there are some uncertainties around parameters and interpretations. The method choices provided high credibility, but due to the project being unique with a few previous cases, it was difficult to compare the results with other investigations.