Monitoring of Tempi Valley Critical Rock Masses: Establishment of Special Monitoring Network and Procedures in Aegean Motorway S.A. Concession Project

Abstract

The paper aims to describe the installed monitoring network of critical rock masses stability and deformations and the procedures that are followed by the Concessionaire in order to ensure the safety of users along the National road in Tempi Valley. The road runs between the mountains of Olympus and Ossa in a canyon characterized by steep rock slopes on both sides, parallel to Pinios River that streams through it. The intense discontinuity systems of the rock slopes could activate planar slide of large rock masses, rock wedges as well as individual rockfall events concluding on the pavement during the roadway operation and therefore could cause accidents and damages on the infrastructure. The concessionaire Aegean Motorway S.A. (AMSA) is responsible for the Operation and Maintenance of this road. For this reason, an extensive rockfall protection and stabilization design for the mitigation of rockfall risks along the National road through Tempi Valley was realized in the years 2009 and 2010. A procedure was established as outlined in detail in the Rockfall Protection Inspection and Maintenance Manual (RIMM) setting out the necessary actions for the continuous inspection of the areas of increased rockfall risks within the Concession Project and for the operation and maintenance of the rockfall protection systems. All rockfall measures as well as rock slopes of the valley are being inspected systematically with any new rockfall event and/or damage to the protection measures documented in designated forms. Moreover, a special geodetic monitoring network has been established in critical rock masses with specific warning and alarm thresholds. The monitoring system of critical rock masses in Tempi Valley is enhanced with grout bridges applied to rock discontinuities where movement is supposed to occur prior to failure. All the collected data are the subject of interpretation by rockfall experts in line with the established procedure.