Significance of Variably Confined Triaxial Testing

by John J. Allen, (A.M.ASCE), Capt., U.S. Air Force., and Inst.; Dept. of Civ. Engrg., Engrg. Mech. and Materials, U.S. Air Force Academy, CO,
Marshall R. Thompson, (M.ASCE), Prof. of Civ. Engrg.; Univ. of Illinois at Urbana-Champaign, Urbana, IL,

Serial Information: Transportation Engineering Journal of ASCE, 1974, Vol. 100, Issue 4, Pg. 827-843

Document Type: Journal Paper


Two types of tests were performed in an earlier study—the constant confining pressure (CCP) test, in which the chamber pressure is held constant during application of the repeated axial stress and the variable confining pressure test, in which the chamber pressure is applied dynamically and varied simultaneously with the axial stress. A sensitivity analysis, consisting of finite element analyses of typical flexible pavement sections, is examined. The granular material resilient parameters are varied over a wide range of laboratory-derived values. The importance of accounting for the stress-dependent properties of paving materials in pavement structural analysis is demonstrated by the drastic changes in stress and deflection distribution effected by the inclusion of stabilized layers beneath unbound granular base courses. The significance of differences in material parameters derived from the two types of triaxial tests are assessed, and it is shown that the less complicated CCP test yields sufficiently accurate results to warrant it continued use as a means of characterizing granular pavement materials.

Subject Headings: Granular materials | Triaxial tests | Axial forces | Construction materials | Pressure vessels | Sensitivity analysis | Finite element method | Stress analysis

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