Even though these correlations are probably site specific, the

ratio of ED to qc obtained in this investigation were within the range

of values reported in the literature. However, since the CPT and DMT

were performed side by side, these correlations are unique and represent

improvements over other correlations which are based on comparison be-

tween field measured qc and laboratory determined deformation moduli.

It also tends to support the argument by many engineers that the cone

resistance, which is primarily an indicator of bearing capacity, can be

related to soil deformation moduli.


 7.4 Evaluation of Resilient Moduli for Pavement Layers

7.4.1 General

 One of the main objectives of this study was to assess the feasibi-

lity of determining the modulus of pavement layers and underlying sub-

grade soils using in situ penetration tests. However, Section 7.3

indicated that the parameters from the penetration tests, especially the

dilatometer modulus (ED), are related to the secant modulus at 25 per-

cent stress levels (E'25). The modulus obtained from NDT generally

represents the initial tangent modulus of the resultant stress-strain

relationship. Because NDT and wheel loadings are generally applied in

short duration of time periods, lower strain levels are obtained.

Therefore, the use of in situ penetration tests' modulus values in

multilayer elastic analysis would be very conservative, and overpredict

pavement response.

 Because qc and ED relate directly to the in situ deformation char-

 acteristics of the soils, it was decided to correlate these parameters

 to the NDT tuned layer moduli. The tuned layer moduli have been