Going Against the Grain

by Peter G. Suah, P.E., (M.ASCE), Pres. and Prin. Engr.; Antillian Engrg. Assoc., Orlando, FL,
Deborah J. Goodings, P.E., (M.ASCE), Assoc. Prof.; Civ. Engrg. Dept., Univ. of Maryland,

Serial Information: Civil Engineering—ASCE, 2001, Vol. 71, Issue 9, Pg. A10-A16

Document Type: Feature article

Abstract: Conventional wisdom has it that granular soils perform better in mechanically stabilized earth (MSE) wall systems. Their properties are well known and simple to express in mathematical terms, and conventional design is relatively rudimentary. By contrast, fine-grained soils exhibit few, if any, of these attributes. However, in recent tests at the University of Maryland funded by the Maryland Department of Transportation, the performance of nongranular soils has exceeded expectations. The tests also show that sliding failure can be predicted using a simple limit equilibrium analysis. The tests showed that marginal soils may be used with geotextile reinforcement for retaining walls of moderate height (up to about 18 m); the reinforcement length is a factor in the locations of the cracks that form, and this affects wall stability; an overlap in the geotextile reinforcement enhances the wall's stability in ways not considered in conventional analyses; failure of geotextile-reinforced walls occurred as a result of shear, overturning, or both, depending on the wall geometry and backfill characteristics; and two-dimensional limit equilibrium analysis methods can explain the behavior of the model soil walls that failed by sliding. Ultimately, the many university tests showed that while granular soils are still preferred for backfill, poorly draining fine-grained soils are suitable—as well as economically attractive—in certain situations.

Subject Headings: Fine-grained soils | Granular media | Retaining structures | Soil stabilization | Soil tests | Tests |

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