The D512 state road is the shortest link between Makarska and Vrgorac. In October 2010, at the site directly before the Stupica ridge, a large rockfall occurred. Under the Stupica location, where the rockfall occurred, there is a very steep slope leading towards the existing arterial road that runs along the coast. In the event of a rockfall and the rolling of large boulders down the slope, there is a high risk of endangerment to the settlement, people's assets existing transmission lines and the arterial roads. This was the largest ever rockfall that had occurred in the Republic of Croatia. The volume of the largest boulders varied from approx. 100 to 250 cubic meters. Following the rockfall, the largest boulders remained lying on the road. A rockfall of this magnitude resulted in large stress changes in the rock mass, thereby threatening the stability of the slope and consequently proving a risk to road safety. Simply removing the fallen boulder pieces and allowing traffic on the road was not possible without undertaking additional measures in securing stability against further rockfalls. In order to eliminate the direct danger to people and property caused by the landslide of rock material, plans were made for constructing a tunnel including additional measures for securing the slope at the tunnel entrance and exit using active and passive rockfall protective measures.
This paper presents the experience gained in geotechnical investigation works, design, construction, supervision, geotechnical measurements and observations during operations. Based on results from completed geological alpine mapping and trajectory simulation of the possible movement of potentially unstable boulders, barriers were designed based on specific numbers, positioning, impact capacity and set heights for protecting against rockfalls.

rockfall, barriers, rockfall protection, tunnel, karst