Hangzhou Bay Bridge - Challenges

Challenges

Because of the many difficulties facing such a tremendous build, almost 600 experts spent nearly a decade designing the bridge. Even after nearly a decade of design, studies, and planning, many different challenges were encountered, the first being the challenge of offshore construction. As a solution, several parts of the bridge had to be completed on land and then transported to the area for which they were built. Some components that were constructed using this process were piers, box girders (bridge panels), and even the bridge foundations.

Another construction challenge involved the weather in the region. Wang Yong, chief director of the Hangzhou Bay Trans-Oceanic Bridge Construction Command Post, described the bridge as being built "in the world's most complicated sea environment, with one of the three biggest tides on Earth, the effect of typhoons and the difficult content of the sea soil." Erosion of materials and cracking and bubbling of any concrete components became a large problem. To combat bubbling and eventual holes, engineers used a cloth-covered template over the concrete. This would improve the color and density of the pieces, making them both more aesthetically pleasing and sturdier. To reduce cracking, engineers used low-strength early-stretching technology when constructing box girders. This technology involves casting (molding) the girder, or bridge panel, letting it harden for no more than three days, and then squeezing it before it reaches its full density. This gives the girder more room to stretch after the bridge is constructed, preventing cracks in the concrete over time.

The third major challenge faced by designers and engineers was an area of toxic methane gas that was discovered roughly 50 meters underground below the location of the bridge. No drilling could be completed before the gas pressure was alleviated. To do this, steel pipes measuring 60 cm in diameter were inserted into the ground, slowly releasing the methane six months prior to drilling.