# Tensile Properties of Granite Under Cyclic Thermal Shock and Loading
## 3 Test Results and Analysis
### Cyclic Loading-Unloading Peak Displacement  
Figure 12 shows the relationship between the peak displacement of the load-displacement curves from the cyclic loading-unloading Brazilian splitting tests on granite and the number of cyclic loading-unloading cycles. This curve intuitively reflects the ultimate deformation experienced by granite during each loading cycle. The curve can be divided into three stages: a rapid growth stage, a slow growth stage, and a failure stage. The rapid growth stage occurs in the early phase of cyclic loading-unloading, typically accounting for about one-third of the total cycles. In this stage, the peak displacement increases rapidly in each cycle--contributing to over 50% of the positive growth in peak displacement--because the water-cooling shock, together with the inherent primary fractures and pores in granite, is compacted under cyclic loading-unloading, resulting in significant plastic deformation [23]. After entering the slow growth stage, the deformation behavior of granite becomes more complex. Generally, as the number of cyclic loading-unloading cycles increases, although the internal pores of granite have become relatively compact, the gradual propagation of microcracks still causes a slight increase in peak displacement; however, some specimens even exhibit a decrease or negative growth in peak displacement, which will be analyzed further below. The failure stage occurs during the final few cycles of cyclic loading-unloading, where the peak displacement increases significantly until it reaches a critical value, leading to the sudden failure of the specimen. For instance, under the conditions of zero water-cooling shocks with preset load upper limits of 65% and 70% (Figure 12a), granite subjected to 500 cycles of cyclic loading-unloading  
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline \multicolumn{1}{c}{**Number of**} & \multicolumn{2}{c}{**Average Tensile**} & \multicolumn{2}{c}{**Number of Cyclic**} & \multicolumn{2}{c}{**Tensile Strength of**} & \\ \multicolumn{1}{c}{**Water-Cooling**} & \multicolumn{1}{c}{**Strength of**} & \multicolumn{1}{c}{**Preset Load Upper**} & \multicolumn{1}{c}{**Loading and**} & \multicolumn{1}{c}{**Cyclic Brazilian**} & \multicolumn{1}{c}{**Reduction**} \\ \multicolumn{1}{c}{**Shock Cycles**} & \multicolumn{1}{c}{**Conventional**} & \multicolumn{1}{c}{**Limit/\%**} & \multicolumn{1}{c}{**Unloading Cycles**} & \multicolumn{1}{c}{**Splitting**} & \multicolumn{1}{c}{**Amplitude/\%**} \\  & & & & & & \\  & & & & & & \\
0 & 13.37 & 70 & 500 & - & - \\  & & 75 & 78 & 9.19 & 31 \\  & & 80 & 39 & 10.52 & 21 \\  & & 65 & 128 & 4.78 & 40 \\
1 & 7.92 & 70 & 96 & 5.  
did not fail, having only experienced the rapid and slow growth stages without reaching the failure stage. In the cases of 0, 1, and 3 water-cooling shocks (Figure 12a-c), the peak displacement of the cyclic loading-unloading load-displacement curves shows a trend of gradual increase with the number of cycles. However, under the conditions of five and seven water-cooling shocks, the evolution of peak displacement with the number of cyclic loading-unloading cycles becomes increasingly complex. For example, after five water-cooling shocks with a 70% load upper limit (Figure 12d) and after seven water-cooling shocks with 70% and 80%  
Figure 12: Peak displacement of granite under cyclic loading and unloading conditions versus the number of cycles of loading and unloading. (**a**) 0 Cycles of Water-Cooling Shock; (**b**) 1 Cycle of Water-Cooling Shock; (**c**) 3 Cycles of Water-Cooling Shock; (**d**) 5 cycles of Water-Cooling Shock; (**e**) 7 cycles of Water-Cooling Shock. load upper limits (Figure 12e), the peak displacement initially increases rapidly during the early cycles but then decreases--sometimes even falling below the initial peak displacement of the granite, exhibiting negative growth.