# Mechanical Behavior of Weathered Granite Exposed to Water
## 3 Test Results
### Stress and Axial Strain
Figure 4: The stress–strain relationship of the fully weathered granites: (**a**) Isotropic consolidation; (**b**) Deviator stress (30%); (**c**) Deviator stress (60%); (**d**) Natural state; (**e**) Saturated state; (**f**) Comparison of stress–strain curves between saturated state and natural state. Further, except for the individual sample (SB-2), the stress-strain curve of the other samples has only two stages, namely the initial stage and the softening stage, as shown in Figure 4e. When the sample reaches the peak stress, it immediately enters the softening stage ([PERSON], 2019 [31]). The initial slope of the stress-strain curve in the saturated state is steeper than that in the natural state, and the strain-softening amplitude of the sample in the saturated state is more noticeable. Similarly, the stress-strain curve of the saturated, fully weathered granite under different consolidation conditions is consistent with its stress-strain curve in the natural state. In general, the above results demonstrate that the strength of the fully weathered rock deteriorates when it is exposed to water, and its strain-softening characteristics are more prominent in the saturated state because water diffuses through the mineral particles along the tiny cracks and pores inside the rock sample during the immersion process. The lubrication and softening effect of water reduces the internal cohesion (c) and the internal friction angle (\(\varphi\)) of the fully weathered granite to various degrees. Figure 5 depicts the stress-strain curves of the sandy fully weathered granite under different consolidation conditions in the saturated and natural states. Like the fully weathered granite, the stress-strain curve of the rock in the natural state can be roughly divided into three stages: an axial strain of 0-8%, 8-17.5%, and higher than 17.5%. However, compared with fully weathered granite, the slope of the stress-strain curve of the sandy weathered granite in the softening stage is gentler, as shown in Figure 5d; in other words, the degree of strain softening of the rock declines relatively. When the axial strain exceeds about 20%, the attenuation amplitude of the deviator stress on the sample is minimal, implying a specific strain-hardening trend. Figure 5e shows that the degree of the strain softening of the sandy weathered granite in the saturated state after reaching the peak shear stress is significant. Especially for the specimen under the isotropic consolidation, the stress attenuation after the stress peak is about 28% of the peak strength. Thus, the interactions between water and rock markedly affect the sandy weathered rock. Moreover, changing the consolidation method from isotropic to 60% deviator stress consolidation raises the axial strain of the rock sample when it reaches the peak stress and increases the shear strength of the weathered rock, which indicates that the deviator stress consolidation has a good effect on the sandy weathered granite. The above results demonstrate that the state of the rock sample, namely the natural or saturated state, impacts on the softening of the sandy weathered rock because water diffuses into the rock mass through pores or cracks, which gives rise to uneven stress inside the rock mass, thereby causing the soil to disintegrate along the direction of the pores and cracks and destroying the soil structure. Figure 6 plots the deviator stress (q) versus the axial strain of the fragmented weathered granites under different consolidation conditions in the saturated and natural states. Except for the saturated sample, all the other samples have different degrees of strain hardening after reaching the peak stress, especially because the fragmented weathered rock is composed chiefly of large pores and a few small pores. The large pores make the water and the internal particles of the rock contact each other completely, which causes the rock to be more prone to disintegration, thereby leading to more significant deformation.