Concerns over the stability of a challenging tunnel on the Cordoba to Malaga high speed rail route has led Spanish rail infrastructure operator Adif to call for specialist assistance.
Technical issues were experienced during the construction of the twin bore Abdalajís Tunnel and Adif remains concerns about ongoing monitoring results more than 10 years after the stucture was completed.
Adif is seeking bids undertake analysis of the instrumentation and survey the 7.3km long tunnel in Andalusia – currently the region’s longest tunnel.
A spokesperson for Adif said: “The terrains traversed by these tunnels are of a great geotechnical complexity and include clays, anhydrites, karst materials with a very heterogeneous mechanical behavior, which led to the adoption of large-scale solutions, among which the construction of reinforcement rings stands out. for its waterproofing, of a length of 1,100m in each tube.
“During the phases of construction and subsequent commissioning of the tunnels, it was considered necessary to monitor their behavior, specifically in the sections of the reinforcement rings, due to the geological and geotechnical characteristics of the terrain they traverse, with high hydrostatic pressures for the aquifers in the area. To this end, more than 2,200 sensors were installed during the execution to control the movements of the reinforcement rings.
“In both tunnels are installed piezometers to measure the hydrostatic pressure, total pressure cells to know the thrust of the terrain in the coating, extensometers, automatic and manual convergences and electro levels.
“Outside the tunnels, and as part of the hydrological monitoring, the meteorological station devices, piezometric level in an external well above the tunnel and a flowmeter in the South mouth of the West tunnel (track II) are also installed and automated.”
Adif has said that it is seeking a partner to undertake regular inspections and analyse the continuous monitoring of automated instrumentation in both tunnels to control the behaviour of the reinforcement rings between vaults 8 and 14.
The twin bore 7.1 km long Abdalajis Tunnel is part of Spain’s high-speed rail network, known as AVE, which links Cordoba, Madrid, Seville and Malaga.
Project promoter owner Gestor de Infraestructuras Ferroviarias (Gif) awarded construction contracts separately for each tunnel in 2001. The east tunnel was awarded to a Dragados-led consortium called Ute Abdalajis, comprising Dragados, Tecsa, Seli, and Jaeger. The west tunnel was awarded to a consortium called Ute Abdalajis Oueste formed by Sacyr and Somague-Engenharia.
The joint ventures shared the main portal site and used nearly identical double shield tunnel boring machines designed by Robbins for Mitsubishi Heavy Industries.
The Abdalajis tunnels pass through a variety of rock types, including dolomitic limestone, quartzite, conglomerates, and sandstone. In the deepest part of the tunnels the strata is heavily fractured and karstic conditions in the limestone were known to hold considerable amounts of water. The entire span of each tunnel contains more than twenty fractured and faulted areas.