Long-Term Pressure Effects on Shear Modulus of Soils

by Sherif S. Afifi, (A.M.ASCE), Staff Engr.; Woodward-Lundgren & Assoc., Oakland, CA,
Richard D. Woods, (M.ASCE), Asst. Prof. of Civ. Engrg.; The Univ. of Michigan, Ann Arbor, MI,

Serial Information: Journal of the Soil Mechanics and Foundations Division, 1971, Vol. 97, Issue 10, Pg. 1445-1460

Document Type: Journal Paper

Abstract: Long-term resonant-column tests were performed on seven air-dry soils to determine their small-strain dynamic behavior under confining pressures maintained for durations up to 803 days. Test results indicate that: (1) The shear modulus of air-dry soils at constant confining pressure increases with time; (2) the shear modulus after 2 years can be predicted within 15% from 2-day tests; (3) the time-dependent increase in modulus increases with decreasing particle size; (4) the time-dependent increase in density under a constant pressure accounts for only 0-15% of the total time-dependent modulus increase; (5) continuous low amplitude vibration (shearing strain less than 0.00001) has no measurable effect on the soils tested over and above the time-dependent modulus increase; and (6) a 10-psi step increase in pressure may destroy up to 15% of the time-dependent modulus accumulated with time in clay, but does not influence sand or silt.

Subject Headings: Soil modulus | Soil pressure | Shear modulus | Soil stress | Time dependence | Soil tests | Shear tests |

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