The picture you see here is one end of the Port of Miami Tunnel, which consists of 2 tunnels being dug that are 42.3 ft in diameter and 4,200 ft long under the Biscayne Bay. The project has 1 billion dollars for its funding and is more than half way complete. What makes this project interesting is that it is the first large diameter tunnel bored through coralline limestone. Coralline limestone is found in the 7th layer, approximately 80-110 ft deep and is extremely porous and unstable. There was a hole drilled approximately every 32 feet to get a complete investigation and understand the nature of the coralline limestone.
A company by the name of Nicholson Construction Co wont the 40$ contract to fill voids in the 7th layer with a grout to keep it stable. Crews drilled 1,000 holes as deep as 120 ft and injected 65,000 cu yards of grout to keep the 7th “Mystery Layer” calm.
It is crazy to me the amount of effort and brains it took to make this amazing project possible. It puts into perspective how much man can achieve. Thankfully there have not been any major injuries through almost three million man hours. I look forward to the completion of this project and will try to keep up to date on any other setbacks they might have. The project is said to begin tests in December.
“Port Of Miami Tunnel Project Features Big Challenges.” Construction, Building & Engineering News: ENR. N.p., n.d. Web. 06 May 2013.
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