Challenge

Madhumati Bridge (also known as Kalna Bridge) is the first six-lane bridge in Bangladesh and is part of the Cross-Border Road Network Improvement Project (CBRNJP). This bridge includes 4.3km of approach road, incorporates four lanes for high-speed vehicles, and two additional service roads.

The CBRNIP was implemented through the Roads and Highways Department (RBD) under the Ministry of Road Transport and Bridges (MORTB). This project was funded by the Japan International Cooperation Agency.

Solution

The Nielsen-Lohse Arch Design

Although regular pile caps used in this bridge construction were 4m below the ground level, pile caps in the middle of the river became 6-8m below the riverbed. The removal of sediment or engineered materials from the bed or banks of a watercourse is known as ‘river scour’. This can occur when the forces imposed by the flow on a sediment particle exceed the stabilising forces.

A cofferdam is a structure that retains water and soil, allowing the enclosed area to be pumped out and excavated dry. Cofferdams are commonly used for construction of bridge piers and other support structures built within water. Cofferdams walls are usually formed from sheet piles that supported by walers, internal braces, and cross braces.

In addition, due to excessive scouring of riverbed, it caused sand boiling in the pile cap area. To stop the sand boiling inside the cofferdam, cement grout was used. The grout was injected by using a grout pump after equalising the inside and outside water level. Five to seven days after injecting the grout, the soil inside the cofferdams is stabilised.

Another challenge the project team faced was the tide in the construction site. A temporary barge and pathway were made available for site staff to work during the tide.

Scope of works:

• Detailed design
• Tender assistance;
• Construction supervision;
• Environmental Management Plan and Environmental Monitoring Plan
• Abbreviated Resettlement Plan

Impact

Through this efficient and reliable new infrastructure, communities of ten southwestern districts will benefit from reduced travel time and improved commerce.

Madhumati Bridge forms part of the Asian Highway Network, which connects the capital Dhaka with the country’s southwestern region, including the country’s biggest land port, Benapole.

Travel distance from Benapole in the Jessore District to Dhaka has been reduced by over 100km whilst the traffic bottleneck created by the ferry crossing over the river has also been alleviated. The bridge also improves safety as people will no longer be forced to cross the river by boat.