Tunnel Waterproofing of the Klokova Tunnel using non-woven geotextile from Thrace NG

The Project

Klokova mountain is located in Aitoloakarnania, Western Greece. Klokova’s tunnel is a twin tunnel, 2950 meters long and is part of the Ionian Highway under construction (concession project), a section of European Route E55. Tunnel boring started in May 2015 and was completed within fourteen months in June 2016. It is among the ten largest tunnels of Greece and the largest one of the Ionian Highway.

Geotechnical Conditions

The rock formations prevailing were basically Cretaceous and Eocene limestones presenting an average compressive strength of 45 MPa. Due to their intense karstification, localized and perched aquifers were present, exhibiting localized water presence of short duration, mostly during rainfalls.

Drainage - Sealing Functions

According to the design a peripheral drainage and a complete waterproofing system consisting of a non-woven of 500 gr/m2 geotextile and a 2mm sealing geomembrane were proposed. The temporary retaining measures included the use of shotcrete reinforced by fibers, rock anchors and steal ribs. For the final lining, drainage and protective geotextile, a geomembrane and cast in place reinforced concrete were used.

Geotextile employed

A non-woven needle-punched polypropylene geotextile of Thrace Nonwovens & Geosynthetics type 500CNW was provided on site, to implement the necessary functions of drainage and protection to the sealing geomembrane. More specifically, prior to the placement of the geomembrane, the shotcreted surface of the tunnel was coated by a non-woven geotextile acting as drainage and as protection preventing any possible geomembrane harm or tear due to direct contact with the inevitable rough surface created by the shotcrete. In total 60,000 m2 of non-woven geotextile was applied in this project.