Resilient Modulus Testing of
Materials from Mn/ROAD, Phase 1
RICHARD L. BERG, SUSAN R. BIGL, JEFFREY A. STARK AND GLENN D. DURELL
reanalyzed. In the regression analysis, the resil-
INTRODUCTION
ient modulus was the dependent variable and vari-
This report describes resilient modulus testing
ous forms and combinations of stress, density, and
that CRREL conducted on materials from Mn/
degree of saturation were the independent vari-
ROAD for the Minnesota Department of Trans-
ables. The equations resulting from this analysis
portation (Mn/DOT). Results of other tests to de-
have been subsequently utilized in the mechanis-
termine physical and behavioral characteristics are
tic pavement design procedure under development
reported separately (Bigl and Berg 1996a). The
at CRREL to predict estimated damage that would
materials tested included samples of the subgrade
occur in some of the Mn/ROAD test sections. Re-
at the site and the two extreme grades of base and
sults of the modeling effort are described in Bigl
subbase designed especially for Mn/ROAD: class
and Berg (1996b).
6 special, a clean base material, and class 3 spe-
cial, a subbase material with a high percentage of
fines. Some specimens were tested in both frozen
METHODS
and subsequently thawed conditions; others were
tested at room temperature without ever having
Materials/conditions tested
been frozen. Two intermediate grades of base--
The materials tested included the two extreme
class 4 special, class 5 special, and an R-70
grades of base--class 6 special and class 3 spe-
subgrade--were manufactured later and results of
cial, and the 1206 and 1232 subgrade samples that
their testing are described in Berg (in prep.).
represent, respectively, the high- and low-heaving
The resilient modulus tests were conducted us-
sandy lean clay (CL) subgrades. Specimens of the
ing repeated-load triaxial test procedures described
base materials were tested in a frozen saturated
by Cole et al. (1985, 1986). The tests involve
condition at three temperatures (class 6 special at
5.0, 3.0, and 2.0C; class 3 special at 7.0,
applying a confining pressure to a cylindrical speci-
5.0, and 2.0C). The same specimens were
men within a cell, while also applying a cyclical
loading of a deviator stress to the top end of the
subsequently warmed to above freezing and tested
specimen. The resilient modulus is defined as the
again at various thawed conditions in a range of
applied deviator stress divided by the recovered
moisture levels created by drawing a suction at
strain upon unloading (the resilient axial strain)
the base of the specimens. Frozen, saturated
for a representative loading cycle.
subgrade specimens were similarly tested at three
temperatures below freezing (7.0, 5.0, and
Linear regression analyses were performed on
2C) and also tested subsequently in a thawed,
the resilient modulus data from the materials tested
in this study. Data from two previously tested ma-
saturated state at room temperature. To acquire
terials that are similar to the intermediate grades
above-freezing resilient modulus data for the
of base/subbase materials (class 4 special and class
subgrade samples at various moisture contents,
5 special) that will be used at Mn/ROAD were
we molded specimens to specified conditions and
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