What is the required percentage of stones to weigh more than 20 kgs in Class A riprap?

In the context of Class A riprap design, the requirement specifies that a certain percentage of the stones must exceed a minimum weight to ensure their effectiveness in stabilizing shorelines or slopes against erosion. The specification that 50% of the stones must weigh more than 20 kgs indicates that at least half of the material used in Class A riprap must be sufficiently heavy. This weight ensures that the stones can resist hydrodynamic forces, particularly in environments with substantial water flow or wave action.

The rationale behind this requirement is tied to the engineering principles of erosion control and material stability. Heavier stones provide better resistance to displacement by water and can effectively interlock with other stones throughout their placement, contributing to an overall stable structure. If fewer than 50% of the stones were to meet this weight criterion, the riprap might not perform as intended, leading to instability and possible failure of the erosion control system.

In contrast, the other options do not meet the standard specified for Class A riprap. Not having a specified percentage falls short of addressing the need for effective material performance, while percentages below 50% may lead to insufficient weight distribution necessary for the structural integrity of the riprap. Therefore, having 50% of the stones exceed