Retaining Wall with No Stone Drainage Column?

VIDEOS, Monster Walls, MESA
By Doug Blackburn, EI
Jan 19, 2009 - 12:15:15 PM

We consulted on four large retaining walls at the Costco Wholesale in Springdale, Ohio and provided construction review services.  These unique walls totaled more than 54,000 sq. ft. and had a maximum height of 42 feet.  MESA Standard blocks and TENSAR geogrids were used with two mechanical comb connectors per block.

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One of the unique features of the walls is that they were constructed without a drainage column of stone immediately behind the wall blocks.  Usually wall designs call for a drainage column of stone to provide:  Compaction, Connection, Filtration, Freeze-thaw protection and Water pressure build up prevention. 

Free-draining SAND was used in the entire geogrid zone and a layer of geotextile was installed to keep the sand from leaking out from between blocks. 

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The sand was placed all the way up to the back of the block and provided Compaction, Freeze-thaw protection, and protection against pore water pressure build-up.  The geotextile provided Filtration so that sand was not lost through the wall.  And finally, Connection capacity was obtained using the MESA mechanical connectors!