30 June 2001
PROCEDURE FOR DETERMINING THE RESILIENT MODULUS
OF GRANULAR BASE MATERIAL
N-1. PROCEDURE. This procedure is designed to determine resilient properties of granular base
(subbase) materials. The test is similar to a standard triaxial compression test, the primary
exception being that the deviator stress is applied repetitively at several stress levels. The
procedure allows testing under a repetitive stress state similar to that encountered in a base
(subbase) course layer in a pavement under a moving wheel load.
N-2. DEFINITIONS. The following symbols and terms are used in the description of this procedure:
a. F1 = total axial stress.
b. F3 = total radial stress, i.e., confining pressure in the triaxial test.
c. Fd = deviator stress (F1 - F3), i.e., the repeated axial stress in this procedure.
d. ,1 = total axial strain due to Fd.
e. ,R = resilient axial strain due to Fd.
,R = resilient lateral strain due to Fd.
g. MR = the resilient modulus = Fd/,R.
h. <R = the resilient Poisson's ratio = ,R/,R.
2 = sum of the principal stresses in the triaxial state of stress (F1 + 2F3 = Fd + 3F3).
F1/F3 = principal stress ratio.
k. Load duration = time interval during which the sample is subjected to a stress deviator.
Cycle duration = time interval between successive applications of the deviator stress.
N-3. SPECIMENS. For base-course materials, 152-millimeter- (6-inch-) diameter specimens are
generally required with the maximum particle size being limited to 25 millimeters (1 inch). The
specimen height should be at least twice the diameter.
a. Triaxial Test Cell. The triaxial cell shown schematically in Figure N-1 is suitable for use in
resilient testing of soils. The equipment is similar to most standard cells. However, there are a
few specialized criteria that must be met to provide acceptable test results. Generally, the
equipment is slightly larger than most standard cells to accommodate the 152-millimeter- (6-inch-)
diameter specimens and the internally mounted load and deformation measuring equipment.