# Mechanical Behavior of Weathered Granite Exposed to Water
## 3 Test Results  
### Stress and Axial Strain  
Figure 4 delineates the stress-strain relationship of the fully weathered granite in the triaxial undrained shear test. According to Figure 4a-c, the stress-strain curve of the fully decomposed granite shows that the shear stress (q) gradually enlarges with an increase in the axial strain before the shear stress on the sample reaches the peak. After reaching the peak, the shear stress gradually decreases with an increase in the axial strain. This observation agrees with the studies of [PERSON] (2004) [27] and [PERSON] (2016) [28] on fully weathered granite. From the peak stress marked in the figure, it can be inferred that the strength of the fully weathered granite in the saturated state is significantly lower than that in the natural state, and the peak strength can decline by up to about 20%, indicating that the mechanical properties of the fully decomposed granite continuously deteriorate under the interactions between water and rock, and its shear strength remarkably declines. The stress-strain curve of the fully weathered rock in its natural state can be roughly divided into three stages, as shown in Figure 4d. In the initial stages of the loading (an axial displacement in the range of 0-10%), as the axial strain increases, the shear stress on the specimen soars, that is, a slight change in the shear stress produces a substantial axial displacement ([PERSON], 2005 [29]; [PERSON], 2016 [30]). At this time, there is an approximately linear relationship between the shear stress and the displacement, and the slope of the stress-strain curve is steep. When the axial displacement exceeds about 10%, the trend of the change in the axial strain with the shear stress varies, the slope of the stress-strain curve decreases, and the stress-strain curve gradually plateaus. Finally, when the axial strain of the sample exceeds about 16% (10% in [PERSON]'s study [29]), the sample enters the softening stage; that is, the shear stress gradually declines with an increase in the axial strain. In addition, the various consolidation methods affect the test results differently. The shear strength of the rock sample under the deviatoric consolidation condition is always higher than that under the isotropic consolidation. The shear strength enlarges with an increase in the deviator stress applied by the deviator stress consolidation. The stress-strain curve of the weathered granite in the saturated state is quite different from that in the natural state. \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Test ID** & **State Before Test** & **Specimen Type** & **Consolidation Method** & \(p\) **(kPa)** \\ \hline SA-1 & & & Isotropic consolidation & \\ SA-2 & Natural & & \((\sigma_{1}-\sigma_{3})_{1}\) & \\ SA-3 & & & \((\sigma_{1}-\sigma_{3})_{2}\) & \\ SB-1 & & Fully weathered granite & Isotropic consolidation & 500 \\ SB-2 & Saturated & & \((\sigma_{1}-\sigma_{3})_{1}\) & \\ SB-3 & & & \((\sigma_{1}-\sigma_{3})_{2}\) & \\ SC-1 & & & Isotropic consolidation & \\ SC-2 & Natural & & \((\sigma_{1}-\sigma_{3})_{1}\) & \\ SC-3 & & & \((\sigma_{1}-\sigma_{3})_{2}\) & \\ SD-1 & & Sandy weathered granite & Isotropic consolidation & 600 \\ SD-2 & Saturated & & \((\sigma_{1}-\sigma_{3})_{1}\) & \\ SD-3 & & & \((\sigma_{1}-\sigma_{3})_{2}\) & \\ SE-1 & & & Isotropic consolidation & \\ SE-2 & Natural & & \((\sigma_{1}-\sigma_{3})_{1}\) & \\ SE-3 & & & \((\sigma_{1}-\sigma_{3})_{2}\) & 680 \\ SF-1 & & Fragmented weathered granite & Isotropic consolidation & \\ SF-2 & Saturated & & \((\sigma_{1}-\sigma_{3})_{1}\) & \\ SF-3 & & & \((\sigma_{1}-\sigma_{3})_{2}\) & \\ \hline \hline \end{tabular} Note: \(\left(\sigma_{1}-\sigma_{3}\right)_{1}\) and \(\left(\sigma_{1}-\sigma_{3}\right)_{2}\) respectively indicate that deviator stress of 30% and 60% of the effective confining pressure is applied for the consolidation.  
\end{table} 
Table 2: The test plan of the triaxial shear tests conducted in the current study.