Tunnel construction in karst environment represents an exceptionally demanding engineering challenge due to the pronounced heterogeneity of the rock mass, the unpredictable occurrence of karst cavities, and complex hydrogeological conditions. The successful execution of such projects requires continuous and comprehensive monitoring of geological, geophysical, and geotechnical conditions, as well as the ability to promptly adapt construction technology when unforeseen karst phenomena are encountered. Timely and coordinated cooperation among all involved disciplines—geologists, karstologists, hydrogeologists, geotechnical engineers, supervisory staff, and contractors—is essential, as only an interdisciplinary approach can ensure safe, time-efficient, and environmentally acceptable construction. When a karst feature is discovered, the construction technology typically needs to be modified: excavation may be temporarily halted or limited, additional investigation and protective measures are introduced, the support system is adapted, and bypass systems are implemented to preserve the natural regime of groundwater flow. Particular attention is given to preventing the increase in hydrostatic pressures, protecting karst aquifers, and preserving the sensitive karst environment. At the same time, minimizing delays and additional costs requires appropriate site organization, enabling construction activities to continue in other excavation phases or working faces when advancement in the tunnel crown is temporarily restricted. This master’s thesis examines principles of tunnel construction in karst environment through the case study of the Second Track railway project Divača–Koper, with a focus on the Beka Tunnel and the discovery of the karst feature 2TDK-025. The case study demonstrates the impact of karst phenomena on changes in construction technology, the decision-making process for the choice on remedial measures the implementation of temporary and permanent remediation measures. It is highlited in the thesis the importance of timely detection and an appropriate technical response of designer, enginere and contractor. The thesis confirms that successful tunnel construction in karst environments is only achievable through continuous monitoring, adaptable construction technology, and strict compliance with nature conservation and hydrogeological requirements.
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