# A Study of Constitutive Model of Rock Damage under the Joint Effect of Load and Moisture
## 3 The Mechanical Test of Sandrock Containing Water
### The Impacts of Water Content on the Mechanical Characteristics of Sandrock  
In order to further explore the impacts of the water content on the mechanical characteristics of the sandstone specimens, based on the experimental results, the relationship between the failure strength, elastic modulus, and water content of the specimens was fitted and analyzed, as shown in Figures 6 and 7.  
\begin{table}
\begin{tabular}{c c c c c c c c} \hline  & _t/h_ & \(\mathbf{\omega_{t}}\)_/\%_ & \(\mathbf{\sigma_{c}}\)/MPa & & _t/h_ & \(\mathbf{\omega_{t}}\)_/\%_ & \(\mathbf{\sigma_{c}}\)/MPa \\ \hline
**A1-1** & Dry & 0 & 91.789 & **A4-1** & 6 & 2.742 & 57.172 \\
**A1-2** & Dry & 0 & 81.508 & **A4-2** & 6 & 2.709 & 59.629 \\
**A1-3** & Dry & 0 & 92.376 & **A4-3** & 6 & 2.834 & 57.153 \\
**A2-1** & 0.75 & 1.611 & 68.809 & **A5-1** & 24 & 2.811 & 56.808 \\
**A2-2** & 0.75 & 1.561 & 64.340 & **A5-2** & 24 & 2.960 & 52.465 \\
**A2-3** & 0.75 & 1.638 & 68.704 & **A5-3** & 24 & 2.912 & 58.207 \\
**A3-1** & 1.5 & 1.977 & 65.309 & **A6-1** & 720 & 2.692 & 55.681 \\
**A3-2** & 1.5 & 1.970 & 65.609 & **A6-2** & 720 & 2.824 & 55.135 \\
**A3-3** & 1.5 & 2.158 & 68.540 & / & / & / & / \\ \hline \end{tabular}
\end{table}
Table 1: Statistics of rock mechanical parameters in uniaxial compression tests.  
Figure 5: The triaxial compression test results of sandrock containing water. (**a**) Dry Sample; (**b**) Sample Submerged for 0.75 h; (**c**) Sample Submerged for 1.5 h; (**d**) Sample Submerged for 6 h; (**e**) Sample Submerged for 24 h; (**f**) Sample Submerged for 720 h.  
Figure 6: The correlation between the water content and the mechanical parameter in uniaxial test. (**a**) \(\sigma\)-\(\omega\); (**b**) \(E\)-\(\omega\).  
\begin{table}
\begin{tabular}{c c c c c c c c c c c} \hline  & \(t\) & \(\sigma_{2}=\sigma_{3}\) & \(\omega_{t}\) & \(\sigma_{c}\) & \(E\) & & \(t\) & \(\sigma_{2}=\sigma_{3}\) & \(\omega_{t}\) & \(\sigma_{c}\) & \(E\) \\  & **h** & **MPa** & **\%** & **MPa** & **Gpa** & & **h** & **Mpa** & **\%** & **Mpa** & **Gpa** \\ \hline  
& & & & \\ \hline \end{tabular}
\end{table}
Table 2: The rock mechanical parameters in triaxial compression tests.  
Figure 7: The correlation between water content and mechanical parameter in triaxial test. (**a**) \(\sigma\)-\(\omega\); (**b**) \(E\)-\(\omega\).  
According to Figure 6, in the uniaxial compression test, with the increase of water content, the failure strength of rock decreases, along with the elastic modulus, demonstrating a relatively clear linear relationship with water content.  
According to Figure 7, in the conventional triaxial compression test, the peak strength and elastic modulus of the sandstone under different confining pressures decrease linearly with the increase of water content, demonstrating a higher level of fitting linear relationship under the condition of the low confining pressure. Meanwhile, a lower confining pressure leads to a larger slope of the fitting curve, indicating that the increase in the confining pressure has a positive effect on restraining rock mass damage.