present the strain distribution up to 5000 cycles. As expected, the
measured strain in geosynthetics kept increasing in the tensile direction,
as shown in Fig. 9, because of plastic strain accumulation.
The data demonstrate that appreciable permanent tensile strains
were developed in geosynthetics, which are believed to help
restrain the lateral movement of the base course aggregates, an
important reinforcing mechanism. The highest tensile strains
(around 0.4e0.8%, depending on the type and location of geosynthetic
reinforcement) were measured directly beneath the
center of the loading plate, where the maximum lateral movement
of the base courses were expected to occur, and became almost
negligible at a certain distance. This distance is about 1.5 D (D:
loading plate diameter) from the center of the loading plate for the
geosynthetics placed at subgrade/base interface and about 1.0 D
from the center of the loading plate for the geosynthetics placed at
the upper one third of the base layer. The maximum measured
strains in geosynthetics were well below the failure strain for
geosynthetics. Similar pattern of strain development was also reported
by Perkins (1999) and Chen et al. (2009). It also should be
mentioned here that the residual tensile strains (around 0.2e0.3%)
were observed in geosynthetics after compaction. These residual
tensile strains in geosynthetics can increase the locked-in initial
stresses in the base course, thus improving the performance of
pavement structure.