Crib pier

A crib pier is a type of pier constructed using a crib structure. A crib is a box-like framework, typically made of timber or concrete, that is assembled in place and then filled with heavy materials, such as rock or gravel, to provide stability and support. Crib piers are commonly used in marine or freshwater environments to support bridges, docks, wharves, and other structures.

The construction process usually involves building the crib on a platform or barge and then floating it to the desired location. Once in position, the crib is sunk onto the seabed or riverbed. The interior of the crib is then filled with ballast material to add weight and provide resistance against the forces of waves, currents, and ice. The superstructure of the pier, such as the deck and supporting columns, is then built on top of the crib.

Crib piers offer several advantages:

• Relatively simple construction: They can be built with readily available materials and do not require specialized equipment or deep foundations in some cases.
• Adaptability to uneven ground: Cribs can be designed to accommodate variations in the seabed or riverbed.
• Cost-effectiveness: In certain environments, crib piers can be a more economical alternative to other pier construction methods, especially when using locally sourced materials.

However, crib piers also have some disadvantages:

• Susceptibility to decay: Timber cribs are susceptible to decay and marine borers, requiring regular maintenance and eventual replacement. Concrete cribs are less susceptible to decay but can still be affected by erosion and chemical attack.
• Environmental impact: The construction of crib piers can disturb the seabed and water quality. The materials used for ballast can also introduce pollutants into the environment.
• Potential for scour: The presence of the crib structure can alter water flow patterns, leading to scour around the base of the pier, which can undermine its stability.

Different types of crib piers exist, including:

• Timber crib piers: Traditionally made of timber, these are now less common due to concerns about durability and environmental impact.
• Concrete crib piers: Constructed from precast or cast-in-place concrete, these offer greater durability and resistance to decay.
• Composite crib piers: Combining timber and concrete, these attempt to balance cost, durability, and environmental considerations.