sive laboratory testing to determine the resilient
AASHTO T99A Proctor Test Specifications. The
modulus of the various subgrade soils as a func-
liquid limit (LL) and plasticity index (PI) for the
tion of temperature. It also provides a guide for
marine clay were 50 and 17%, respectively.
selecting the appropriate resilient modulus values
to be used in the current AASHTO design method.
These values can also be used in future modifica-
TEST PROGRAM
tions to the AASHTO design method as proposed
in the current AASHTO 2002 design guide research
In accordance to AASHTO TP46-94 (1996b), the
study.
coarse gravelly sand (A-1-a) and the silty glacial
till (A-4) were compacted into 152-mm- (6-in.-)
diam. 30-mm- (12-in.-) high samples, These soils
DESCRIPTION OF TEST SOILS
are designated as base/subbase materials accord-
ing to AASHTO TP46-94. The remaining sand (A-
The five test soils selected for this project, after
1-b) and fine-grained soils (A-2-4 and A-7-5) were
compacted into 71-mm (2.8-in.) diam. 152-mm (6-
discussion with NHDOT personnel, reflected
most, but not all, of the subgrade soils in New
in.) height. These soils are designated as subgrade
Hampshire. With the exception of the marine clay,
soils, according to AASHTO TP46-94. The sample
the grain size gradation and moisture density re-
preparation procedure was similar to that devel-
lationships were provided by the NHDOT. The
oped by Baltzer and Irwin (1995). Details of the
grain size gradation, Atterberg's limits, and mois-
compaction study are provided in Appendix A.
ture density relationship for the marine clay were
The samples were compacted in five layers us-
conducted at CRREL. The gradations are shown
ing a CS 1200 electrohydraulic kneading compac-
in Figure 2. The classification and optimum mois-
tor manufactured by James Cox & Sons, Inc. (Fig.
ture density are shown in Table 1. All moisture
3). This kneading compactor can be programmed
density relationships were developed using the
for pressuretime curves, repetition of rates, ex-
100
80
60
40
Silty Glacial Till
Coarse Gravelly Sand
Medium Fine Sand
20
Silty Fine Sand
Marine Clay
0
10 2
10 1
10 0
10 1
10 2
10 3
10 4 mm
10 0
10 1
10 2
10 3
10 4
10 5
in.
Grain Size
Figure 2. Grain size distribution for test soils.
3
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