Mithi River CLC Bridge (Mumbai Metro Line-2B)

As part of the Mumbai Metro Line 2B Corridor, a major design challenge arose at the Mithi River crossing: a long-span viaduct had to be constructed through a severely space-constrained, densely urbanized zone, immediately adjacent to protected riverbanks and sensitive existing infrastructure. Initially part of a full-package design by Structcon Designs Pvt. Ltd., Spannovation was engaged as the specialist bridge consultant to re-engineer the critical balanced cantilever segment over the river.

The 270 m bridge comprises three spans (75 m + 125.25 m + 70 m) with a horizontal radius of 210 m. Designed as a single-cell, cast-in-place post-tensioned box girder, the structure uses twin-blade integral piers. However, due to site limitations—including skewed, eccentric foundations and extremely shallow rock sockets for pile foundations (only 6–10 m deep)—the substructure remained rigid. This rigidity led to large creep, shrinkage, and thermal force demands. To counteract these long-term restraining effects, we used Pre-Compensation Force Method (PFM). After iterative analysis, a 5000 kN pre-compensation force was applied using synchronized hydraulic jacks. This pre-emptively induced stress profile helped neutralize the effects of excessive restraining demands, particularly in the pile foundations.

An unexpected challenge emerged due to the bridge’s tight curvature: the pre-compensation force induced a lateral twist about the piers, resulting in an 83 mm transverse displacement at the cantilever tip. To resolve this, plan pre-camber (horizontal curvature correction) was introduced—an uncommon yet necessary strategy to ensure final geometric alignment at service stage. This project exemplifies how engineering innovation and advanced analysis can come together to address constraints in dense urban environments, while delivering long-term durability, constructability, and cost efficiency.