Cutting protection at the entrance of a tunnel passing through unstable slopes

The Sveti Marko tunnel was built on the Zagreb-Rijeka motorway. The approach cutting and the hillside portion of the tunnel pass through an unstable hillside. The protection of the cutting was designed and performed using shotcrete as well as the IBO and IBI anchors. The excavation was realized using horizontal and vertical links. The measurement system applied was quite complex: vertical deformeters and inclinometers, horizontal deformeters, geodetic measurements and measurement of forces in anchors. The entry to tunnel was protected by a pipe roof. The rate of progress and the support system were confirmed on trial sections.