Attempts to stabilize and dissipate energy at the bottom of a 30-ft. drainage “let-down” structure with rock riprap for BP/Amoco’s Joliet, Illinois facility proved futile. Thousands of dollars had been invested into this project over the years and nothing had proven to be effective.
In 1998, Patrick Engineering decided to try a more proactive engineered approach to this difficult application. The A-Jacks interlock against one another, forming a matrix weighing in excess of 7,800 pounds of interlocking - erosion protection and energy dissipation. Utilizing approximately 100 24-in. A-Jacks concrete armor units, the solution proved to be both cost-effective and stable.
The A-Jacks were wrapped with a polyester cable for additional stability to keep the individual units from dislodging from the matrix. As water tumbles down the concrete steps, the units break up the energy from the water before it cascades into a northern Illinois stream.
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