Planning and Karstological Monitoring of Construction of the Railway Line Crossing Classical Karst (Slovenia)

The ZRC SAZU Karst Research Institute is collaborating on individual projects related to the development and protection of natural and cultural heritage in karst areas. Karst areas make up as much as 43% of Slovenian land and more than 50% of our water supply comes from karst. Slovenia is home to the Classical Karst from where the first international descriptions of karst features originate. We are aware of the need to regularly and effectively impart knowledge of karst to the wider social community, also by collaborating on important projects with direct application. We have built the foundation for sustainable planning of life in karst areas. The rail link between the Northern Adriatic port in Koper (Slovenia) and inland Slovenia, initially part of the Pan-European Transport Corridor V (Venice-Kiev), required extensive karstological planning.

The line will run through the karst massif in two longer tunnels. There is a high probability that the two tunnels will intersect karst caves, as the entire area is highly cavernous. It is very likely that somewhere between 5 and 15 caves will open up per route kilometre. The passages can measure over 10 m in diameter. In some places between the surface and the phreatic zone we can expect cave passages and systems, products of older speleogenetic phases. The two tunnels traverse several contacts of limestone and flysch, where there is a high probability of coming across caverns and a fluctuating groundwater table. We can almost certainly expect that karst caverns will be encountered there during the construction of the tunnels. We have deduced from the research conducted in boreholes and the experiences gained during the construction of motorways that the entire karst massif is highly karstified. There is a high probability of encountering shafts along the entire route that drain water to the karst groundwater level. By understanding the basic hydrogeological conditions, mostly owing to the results of the three tracer experiments conducted, we have been able to deduce the directions and characteristics of the flow of groundwater from the planned railway route, and the endangerment of karst water sources within its impact area.

We have made our best efforts to develop integral karstology, which uses select approaches to learn about and understand the uniform, three-dimensional karst landscape. The specific research conditions have enabled us to get a good idea of the karst that will be traversed by the railway. Although we could not precisely pinpoint the locations of caves that will open up during construction, nor all the waterways that shape and connect the karst, we were able to clearly predict what can be expected during construction and how the construction should take place. The intense construction work that was begun in the beginning of this year will be more successful because of our findings. We will be able to protect a greater number of newly discovered karst features, which are an important part of our natural heritage. Moreover, the important sources of water supply will be protected more efficiently.