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need for additional laboratory-based studies for validation,
requirements of stress analysis, and other factors.
Most of the assessments noted in these tables are based
on the technical information available to the author, and
because it is subjective, these assessments should be consid-
ered as suggestive assessments.
Resilient Moduli Magnitudes
A summary of moduli of various bases and subgrade mate-
rials is presented in this section. The moduli ranges from
study to study are different, and these variations are attrib-
uted to material and sampling differences as well as to test
procedure and equipment variations. Because it is not prac-
tical to summarize this information in this synthesis, some
of the moduli information from a few studies (including one
from an LTPP study) is presented in Appendix D.
FIGURE 86 Comparisons between measured and predicted
moduli of fine grained soils (Titi et al. 2006). The recommended approach to determine the resilient
moduli of soils is to test and measure the moduli of subgrade
Table 19
Comprehensive Assessments of Various Methods for Determining Resilient Properties—Part I
Subgrades Relationship
with Design Skillled
Unbound MR (nature of Is this Method Personnel Time to Perform Cost
Method Clayey Sandy Bases correlations) Standardized? Required? (quick/long) (relative)
Y (direct,
Lab—RLT Y Y Y Y Y Long High
Level 1)
Lab—Resonant N (indirect,
Y Y Y needs Y Y Long Moderate
Column Poisson’s ratio)
Lab—Others N, indirect Low to
Y Y Y Y N Quick
(CBR, R) (Level 2) Moderate
N, direct Low to
Field—FWD Y Y Y N Y Quick
(Level 1/2) Moderate
N, indirect Low to
Field—Geogauge Y Y Y N N Quick
(Level 2) Moderate
N, indirect Low to
Field—PSA Y Y Y N N Quick
(Level 2) Moderate
N, direct
Field—LFWD Y Y Y N N Quick Low
(Level 1/2)
N, indirect
Field—DCP Y Y N Y N Quick Low
(Level 2)
Moderate
Field—CPT Y Y N N, indirect; R N Y Quick
to High
Note: Y = yes; N = no; R = needs more research.
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Table 20
Comprehensive Assessments of MR Prediction Models
Applicable Needs Stress
Additional Estimation Need
Laboratory in the More
Unbound Studies for Bases and Data and
Model Type Subgrade Bases Repeatability Reliability Verification? Subgrades Research?
Direct Correlations Based on Moderately
Y Y Y Y Not Needed Y
Laboratory Determined Parameters Reliable
Direct Correlations Based on Field Moderately
Y Y Y Y Not Needed Y, R
Determined Parameters Reliable
Low to
Indirect Correlation Parameters—
Y Y Y Moderately Y Needed Y
2 Model Constants
Reliable
Moderately
Indirect Correlation Parameters—
Y Y Y to Highly Y Needed Y, R
3 Model Constants
Reliable
Note: Y = yes; N = no; R = needs more research.
Table 21
Comprehensive Assessment of Various Methods for Determining Resilient Properties—Part II
Applicable Applicable in Non-
in New Applicable QC/QA for Destructive Needs Additional
Sampling Pavement in Pavement Base/Subgrade Nature of Correlations Lab Studies for
Method Needed? Construction? Rehabilitation? Compaction? Testing? Type? Verification?
Lab—RLT Y Y Y N Y Semi-empirical N
Lab—Resonant
Y Y Y N Y NA N
Column
Lab—Others
Y Y Y N N Empirical Y
(CBR, R)
Theoretical Y (validation of
Field—FWD N Y Y Y Y (back backcalculated
calculated) moduli)
Theoretical Y (validation of
Field—
N Y Y Y Y (back interpreted
Geogauge
calculated) moduli)
Theoretical Y (validation of
Field—PSA N Y Y Y Y (back interpreted
calculated) moduli)
Theoretical Y (validation of
Field—LFWD N Y Y Y Y (back interpreted
calculated) moduli)
Y (validation of
Field—DCP N Y Y Y N Empirical interpreted
moduli)
Semi- Y (validation of
Field—CPT N Y Y Y N empirical to interpreted
empirical moduli)
Note: Y = yes; N = no; NA = not applicable; R = needs more research.
