Sand and Glacial Till Soil

Soil Courses, VIDEOS
By Joseph Kowalski
Sep 25, 2008 - 5:27:16 PM

During segmental retaining wall design there are a minimum of three soils around or inside the wall that must be studied.  Inside the geogrid-reinforced zone we call the soil the "Reinforced Soil".  Most of the time within this zone, we use SAND.  Sand is excellent because:

      • it is relatively inexpensive;
      • it is very easy to compact;
      • it is easy to place and spread;
      • it is only minimally affected by weather, so construction delays are rare;
      • it has a relatively high friction angle (so we can use less geogrid); and,
      • it does not readily allow the buildup of water pressure.

The soils below the retaining wall are called the "Foundation Soils".  At the site in this video, the foundation soils are very stiff undisturbed glacial till soils.  Three test borings revealed deep deposits of very stiff soil that is excellent for bearing capacity of the retaining wall.

The soils behind the retaining wall are called the "Retained Soils".  At this site the retained soils also consist of very stiff undisturbed glacial soils.  The soils are very stiff glacial lean clays (different than Glacial Till because there is not much silt, sand, gravel or cobbles present).