Sewer Trunk Main, Jubail Industrial City
A 450-metre gravity trunk main micro-tunnelled to precise grade through saturated ground.
Diameter
Length
Depth
Duration
Completed
The Challenge
A gravity sewer only works if it holds its fall. This drive ran through water-bearing sand below the water table, where conventional excavation would have required extensive dewatering and risked settlement beneath adjacent industrial plant.
Our Approach
A slurry-shield micro-tunnelling machine was launched from a shaft at the upstream end, with face pressure balanced against groundwater to hold the surrounding ground stable. Line and grade were monitored by laser from a surface control cabin and corrected continuously across the drive.
The Outcome
The full 450 metres was completed to within 20mm of design grade with no dewatering and no measurable settlement at the surface. The line was commissioned on the authority's original programme date.
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