298
results from calibration chamber tests in which Eg was found to be equi
valent to the secant modulus at 25 percent stress level (E'25) for
normally consolidated cohesionless soils. Similar correlations between
E'25 and qc suggest that the ratio of E'25 to qc varies from 2 to 10 or
more depending on the stress history, relative density and mineralgica!
composition of the soils (50). This suggests that Eg and qc are related
which is generally verified by comparing the trends illustrated in
Figures 7.3 to 7.7.
Regression analysis of Eg and qc values were performed for each
test pavement site. The results of these analyses are given in Table
7.1. Note that the analysis utilized average values of Eg and qc from
each test site. Regression equations for the three SR 26 sites and SR
15C were almost identical although their R2 values varied from 0.75 to
0.97. The other test sites had higher constants with the exception of
SR 15B in which the lowest slope--2.519--was obtained.
Table 7.1 Relationship Between Eg and qc for Selected
Test Sections in Florida
Test Road
County
Number of
Observations
R2
Regression Equation
SR 26A
Gilchrist
24
0.850
=
3.199
c
SR 26B
Gilchrist
26
0.860
ed
=
3.201
qc
SR 26C
Gilchrist
21
0.969
ed
=
3.384
qc
US 301
Alachua
31
0.878
eD
=
5.351
qc
US 441
Columbia
26
0.881
Ed
=
4.188
%
SR 12
Gadsden
28
0.915
ed
=
4.191
qc
SR 15B
Martin
21
0.900
ed
=
2.519
qc
SR 15C
Martin
22
0.752
ed
=
3.300
qc
SR 715
Palm Beach
25
0.850
eD
=
5.330
qc