In an open caisson foundation, how many feet in diameter is the hole dug?

In an open caisson foundation, how many feet in diameter is the hole dug?

• A. 2 to 5 feet
• B. 1 to 3 feet
• C. 4 to 6 feet
• D. 5 to 8 feet

Answer: (A)

In an open caisson, the excavation is done through a bottom-open shaft, and the opening created for digging is kept relatively modest in size. The hole diameter is typically about 2 to 5 feet. This size provides a practical balance: it’s large enough to remove soil and to accommodate installation of reinforcement and formwork as the caisson is sunk, but small enough to keep the sidewalls stable and to minimize water inflow and the need for heavy temporary bracing. Diameters much smaller would hinder excavation and equipment access, while larger diameters would require far more bracing and significantly higher costs, making them impractical for standard open caisson work.

In an open caisson, the excavation is done through a bottom-open shaft, and the opening created for digging is kept relatively modest in size. The hole diameter is typically about 2 to 5 feet. This size provides a practical balance: it’s large enough to remove soil and to accommodate installation of reinforcement and formwork as the caisson is sunk, but small enough to keep the sidewalls stable and to minimize water inflow and the need for heavy temporary bracing. Diameters much smaller would hinder excavation and equipment access, while larger diameters would require far more bracing and significantly higher costs, making them impractical for standard open caisson work.