3.4 Results of Laboratory Testing
This section provides a presentation and discussion of the creep and cyclic testing
of TerraFlex specimens.
3.4.1 Creep Testing
The isochronous stress-strain curves from the creep tests are shown in Figure 3.1.
As can be seen from this figure, there is a progressive decrease in the slope of each curve
between 0 psf and 400 psf compressive stress. Above 400 psf, the slopes of the curves
begin to increase.
3.4.2 Cyclic Testing
The experimental results from the 0.1-hour duration cyclic tests are shown in
Figure 3.2. As can be seen from this figure, two tests were performed with 7 load/unload
cycles. There was a significant amount of permanent deformation in the material,
especially after the first loading cycle, which can be seen by the strain offset between the
first loading and unloading stages. The strain-offset behavior continued to occur for all
the cycles, but to a lesser degree than the first cycle. The amount of strain on the seventh
loading cycle was on the order of approximately 20 percent for both tests. The data also
show that the slopes of the load curves increase due to cyclic loading.
The experimental data for the 1-hour duration tests is shown in Figure 3.3. This
figure shows that there was significant permanent deformation of the TerraFlex with each
cycle. For these tests, the TerraFlex samples experienced strains on the order of 40
percent after seven cycles. Again, the data show that the slopes of the loading curves
increase due to cyclic loading.