Ourika tunnel (Morocco) – Geological survey of alternative routes Preliminary design


The Ourika tunnel is a major road infrastructure project, which is similar to the Mont Blanc tunnel (France) in many aspects:

  • its length of about 10 km,
  • the impossibility of any surface route,
  • the crystalline nature of the massif,
  • the coverage height exceeding 1000 m.

The structure must allow to cross the Moroccan High Atlas, hence facilitating the connection between the economical and touristic cities of Marrakech and Ouarzazate, while avoiding the Tizi N’Tichka pass (2260 m) and 60 km mountain roads. The massif crossed by the project reaches an altitude of 3900 m.

The project’s feasibility study included 2 alternative solutions which needed to be chosen from.
The inaccessibility of the site led TERRASOL to organise a 5-day mission on foot in partial self-sufficiency, walking along the major part of the linear of both routes in order to:

  • define the potential implantation sites of the portals,
  • describe the main geological formations encountered by the future tunnel,
  • localise the main tectonic accidents,
  • identify the potential site for an intermediate decline (access tunnel).

Upon completion of the soil-testing campaign and analysis, TERRASOL produced a comparison of both alternative solutions: alternative solution A is short with a gentle slope, whereas alternative solution B has a much better geological context, and allows to build an intermediate decline.

TERRASOL defined a specific soil-testing campaign focused on the sites of crucial interest for the project, ensuring they were considered properly during the preliminary project phase.

Terrasol’s achievements:


  • Survey of the geological context of the project
  • Comparative analysis of the geological conditions of both alternative routes
  • Preparation of the soil testing campaign
  • Geotechnical preliminary studies
Characteristics
PERIOD :  2004-2008
Project owner & client : Ministry of infrastructures of the Kingdom of Morocco
Project Manager : Provincial Direction of ainfrastructures of El-Houaz
Group of design offices : Maroc Setec, Setec TPI, Terrasol
Turnover 50,000 €
Main specifications :  

  • Crossing the High Atlas
  • Connection between Marrakech and Ouarzazate
  • Tunnel project 9 to 11km long
  • Two potential alternative routes to compare
  • Isolated project area