## 3 Results and Discussion  
### Analyzing the Behavior of Samples under Dry and Saturated States  
After conducting the fracture toughness test on the selected limestones, it was observed that in most of the samples, including sandy limestones, dolomite limestones,  
Figure 6: Wideness of the chevron crack (**A**), cross-section of the chevron notch (**B**), loading mode-I before failure (**C**), and loading mode-I after failure (**D**).  
floatstones, and mudstones, the fracture toughness was lower in the saturated state than in the dry condition. However, the toughness values of the wackeston, packstone, grainstone, and framestone samples did not show any dependency on the saturation state. To investigate this, factors such as the porosity, petrography of thin sections, and mineralogy of the samples were examined.  
Samples R20 and R18 were two wackeston samples and both contained kaolinite. If the presence of this clay mineral had an effect on the toughness value in a saturated or dry state, we would have seen the same behavior in these samples as well, i.e., less fracture toughness under a saturation condition. Thus, it can be somehow concluded that the presence of kaolinite had no effect on the variations of toughness as a function of the saturation state. The porosity of the R20 and R18 samples was equal to 1.5 and 2.6, respectively. In general, it was observed that porosity was the most dominant factor affecting the variations of fracture toughness for wakestone, packstone, grainstone, and framestone, which did not show any particular trend considering the saturation state. In the samples with a porosity of more than 2.5%, the fracture toughness decreased under the saturated state, while the samples with a porosity less than 2.5% showed a higher fracture toughness under a saturated state.  
Samples R15, R4, and R23 were placed in packston category in terms of petrography. According to the XRD and EDS analyses, the R15 sample contained the montmorillonite clay mineral (Figure 7). It is notable that, in this sample, the fracture toughness was higher under a saturated state. The porosity of the R15, R4, and R23 samples was 1.5, 2.3, and 6.9, respectively. Again, it was observed that, irrespective of mineralogy, porosity is the main factor controlling the fracture toughness as a function of the saturation state. In the studied packstone samples, if the porosity was higher than 2.5%, the fracture toughness was higher under a dry state, but if the porosity was less than 2.5%, the fracture toughness was higher under a saturated state.  
Samples R14, R3, R6, and R13 were categorized as grainstone according to their petrography, and their porosity values were equal to 1.6, 1.7, 1.7, and 3.2 respectively. R14 contained broken particles (Figure 8), R3 contained glauconite clay mineral, and R6 contained both glauconite clay mineral and broken particles, as well as microcracks. All of these samples showed higher fracture toughness values under the saturated state, and the only common parameter in these samples was a lower porosity.  
Figure 7: Result of XRD and EDS experiments for R15.  
Therefore, the presence of water-sensitive clay minerals in the samples of wackeston, packston, and grainstone had no effect on the variations of fracture toughness as a function of the saturation state, and the only factor affecting it was the porosity of the sample. It should also be mentioned that the R1, R2, and R10 rock samples contained glaucoma; the R11, R29, and R30 rock samples contained montmorillonite; R18 contained kaolinite; and sample R9 contained palygorcite. According to our analyses, because of the high porosity values of these rock samples, which were more than 2.5%, their fracture toughness values were lower under a saturated state.