Stable Power Supply in Croatia: DSI delivers Special Systems for Service Tunnel

The city of Dubrovnik in the far south of Croatia is primarily supplied by electricity from the 126 megavolt amperes (MVA) TS Komolak transformer station in the city’s North West. From there, electricity is relayed to a transformer station located near the town of Plat via two 35kV lines.

In order to expand the region’s power supply system, the owner HEP is currently adding new lines to the only existing power supply, which currently has a limited capacity. For this purpose, two new transformer stations are being built: the 110kV TS Srd station, the 220/110/20kV TS Plat station and a newly planned 220kV high-voltage line. The project also includes the construction of a 374m long service tunnel. This new tunnel will connect the two transformer stations and the existing tunnel system. All of these measures will considerably improve the entire power supply system. The tunnel portal is located on the connecting road between Dubrovnik and Cavtat and leads to the old connection tunnel at an inclination of 18 degrees. The tunnel is stabilized conventionally using roof support products and shotcrete, and the advance is carried out using the drilling and blasting method. DSI produced and supplied Type P95-20-30 3 bar Lattice Girders as passive roof support for stabilizing the excavated cross section of the service tunnel. Lattice Girders are used as a true-to-form template for shotcrete application and ensure an easy and quick assembly as well as simple handling of the supporting structure. Additionally, lattice girders offer optimum bond and interconnection with the shotcrete lining while simultaneously minimizing shotcrete spray shadows. The system also ensures simple adjustment and shaping to the excavation geometry. Additionally, DSI Austria also supplied Type R32-280 DSI Hollow Bar Rock Bolts and system accessories. DSI Hollow Bars can be used without difficulty even in unstable boreholes, thus offering a convenient alternative to systems that have to be installed using time-consuming cased or conventional drilling methods. Minor space requirements for installation and the easy adjustment of the single-use drill bits to varying ground conditions are additional decisive advantages of this system. All of the roof support products were produced by DSI on time and supplied to the jobsite just in time for installation.