Lateral Pressures from Soft Clay

by Peter J. Moore, Reader in Civ. Engrg.; Univ. of Melbourne, Australia,
Graham K. Spencer, Engr.; Coffey and Hollingsworth, Consulting Engrs., Melbourne, Australia,

Serial Information: Journal of the Soil Mechanics and Foundations Division, 1972, Vol. 98, Issue 11, Pg. 1225-1244

Document Type: Journal Paper


Following cessation of retaining wall movement earth pressures from soft clay having liquidity indices equal to or greater than unity creep back to the at-rest value. The rigid model retaining wall tests indicate that reductions in the lateral pressure occur immediately when wall movements are induced. The conventional active pressure distribution is produced when the wall is subjected to a horizontal displacement of approximately 5% of the wall height. Immediately after the wall movements are terminated the lateral pressure increases, with the long-term pressure equalling the lateral pressure acting before wall movement was initiated. This long-term pressure can be calculated by means of an expression which is similar to the conventional long-term active pressure expresion but with the relaxed shear strength being considered as the mobilized shear stress in the backfill. The relaxed shear strength may be measured in torsion shear tests. Alternatively the long term pressure may be calculated from values of the rest coefficient Ko which can be measured through tests in a special triaxial cell.

Subject Headings: Shear strength | Lateral pressure | Soil pressure | Shear stress | Shear tests | Retaining structures | Clays | Soft soils

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