sequences (Tables 1 and 2) produced very small deformations. It was difficult to
distinguish the response of the test specimen from the noise in the system. A series
of static confined compression tests were carried out to determine the deviator
stress at which the specimen response was still linear and produced sufficient de-
During some of the frozen tests, some load sequences were increased so that a
signal from the transducers could be obtained for recording. When shear tests were
performed, they were conducted using a constant piston rate of 3.05 mm/minute
in displacement control. The loading sequence used for the test program are shown
in Tables 7 to 12. The seating load in all cases was set to 10% of the maximum axial
load as done in AASHTO TP 46.
Confining pressure was applied to the test specimen via the in-house pressur-
ized air system. A bleeder type regulator was used to obtain the desired pressure,
and a pressure transducer was used to monitor the confining pressure through out
the test. A miniature, high-precision load cell mounted inside the triaxial cell on the
loading piston was used to monitor the load applied to the specimen. The speci-
mens were preconditioned with 500 load repetitions.
National Instruments Labview data acquisition software was used to collect the
raw data. For the resilient modulus tests, each load sequence contained 100 cycles
as long as the permanent displacement was within 5%. The last five cycles were
recorded and stored for analysis. Data were acquired at 500 Hz. For the shear tests
and hydrostatic compression tests, data were acquired at 5 Hz. The resilient modu-
lus was determined by the method described in AASHTO TP46.