Articulated Concrete Block
Articulated concrete blocks (ACBs) are a flexible revetment system that provide effective erosion control and can also include plantings to maintain a natural appearance. Articulated concrete blocks are effective and economical for a wide range of erosion problems, and are easily installed above or below the water line, as either cabled or non-cabled systems.
Articulating concrete block (ACB) systems are used to provide erosion protection to underlying soil from the hydraulic forces of moving water. An ACB system is comprised of a matrix of individual concrete blocks placed together to form an erosion-resistant revetment with a geotextile underlay for subsoil retention. The term “articulating” implies the ability of the matrix to conform to minor changes in the subgrade while remaining interlocked with or without the use of cables, geotextiles or geogrids. The interlocking property provided by the special shapes of ACBs also allow for expansion and contraction. They are either hand-placed or installed as preassembled mats on top of a filter layer on prepared subgrade, and act as a soil revetment. Several varieties of ACB systems are available: interlocking, cable-tied and noncable-tied matrices, and open cell and closed cell varieties. Open cell units contain open voids within individual units that facilitate placement of aggregate and/or vegetated soil. Closed cell units are solid, concrete elements that are capable of allowing vegetation growth between adjacent units.
The ACB system includes a filter component that allows infiltration and exfiltration to occur while retaining the soil subgrade. The filter layer requires a geotextile to provide particle retention of the soil subgrade and may include a granular transition layer. In some cases a highly permeable drainage layer, either granular or synthetic, may be included in the system to provide sub-block pressure relief, particularly in turbulent flows, or wave-attack environment. The blocks within the matrix must be dense and durable while providing a matrix that is flexible and porous.
Articulating concrete blocks can be used in a broad range of erosion control applications with good success. Since ACB systems have a very high armoring potential, application is not limited to subcritical flow or locations of low turbulence. ACB systems have been used with excellent success at installations generating high velocities such as culvert outlets, spillways, and grade control structures. In many laboratory studies, ACB systems have maintained structural stability in flow velocities conditions exceeding 20 fps (6 m/s), where failure was defined as any loss of contact between the block and the subgrade. In many geographic regions, ACB systems offer a less expensive and more aesthetic alternative to other treatments, not addressed in this manual, such as riprap, structural concrete, rigid grout filled mats (pump mats) and soil cement.
ACB systems are well suited to channel lining applications, in particular for lateral stream stability. The articulating characteristic allows the systems to be placed effectively at bends and regions of vertical change, such as sloping grade control structures. Many ACB systems are manufactured with voids or open cells to accommodate vegetation.
ACBs systems are easy to install, simple to produce, and environmentally friendly.
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US/Mexico Border Fence
Marfa Sector, TX
Chevron Tank Farm
St. Lucie, FL
Royal Lake Dam
Fairfax County, VA