Project Outline The Tehran metro system is a project of immense national importance which, when completed, is destined to radically transform Tehran’s transportation network. Due to the complex nature of the project, the tunneling program encompassed a variety of innovative design and construction techniques.

The Tehran metropolitan area has a diverse and challenging geology, including soft and sandy soils. An important success factor for Tehran metro’s tunneling program was, therefore, that the challenges posed by the geology be identified up-front on a segment-by-segment basis, and effective solutions be then derived and implemented to overcome potential difficulties. Specifically, efficient underground system waterproofing techniques had to be used to provide completely dry tunnels.

The Tehran metro’s tunnels were executed via open-trench, Austrian/shotcrete supported and concrete segmental lining methods.

Scope of Work

• Involved: Drilling and contact grouting to strengthen the soil contact with the tunnel’s segmental lining
• Drilling and grouting in order to make an impermeable curtain to prevent underground water seepage and consolidate decompressed zones caused by underground excavation.
• Ongoing control of construction specifications prior to and after grouting operations.
• Performing waterproofing tests following investigation drilling and upon completion of each stage of grouting.