National Concrete Masonry Association Manual Addition

The National Concrete Masonry Association Creates a Third Edition for State of The Practice Design of Retaining Walls.

Previous National Concrete Masonry Association (NCMA) manuals have had limited information regarding the effect of water on wall stability. The NCMA added a third edition to the Manual in 2006 to discuss the design of retaining walls bearing capacity under various groundwater conditions.

The third edition focuses the ground water table behind retaining walls and the impact on the hydrostatic load. The NCMA assumed that the groundwater table is two thirds the height of the wall. This is used for creating design recommendations and wall structure analysis. The manual also mentions that there are many cases in which internal drainage cannot effectively remove groundwater from a retaining wall. In this case the hydrostatic pressure builds up and must be considered. The design of retaining walls and the reinforced soil mass must be created to counteract this issue.

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