# Mechanical Behavior of Weathered Granite Exposed to Water
## 5 Conclusions  
This paper conducted a series of indoor undrained triaxial shear tests to examine stress and strain development of weathered granite in its natural and saturated states. To this end, the changes in the mechanical properties of the weathered granite exposed to water were analyzed, and the influence of the different consolidation conditions on the stress-strain curve of the weathered granite was discussed. In addition, a strain-softening model suitable for the natural and saturated states of weathered granite was developed to analyze the measured axial strain. From the above results and discussion, the following conclusions can be drawn:  
1. The stress-strain curve of the weathered granite in its natural state can be roughly divided into three stages. In the initial stage, which happens at an axial strain of lower than 10%, 8%, and 5% for the fully weathered granite, the sandy weathered granite, and the fragmented weathered granite, respectively, the shear stress on the specimen soars with the axial strain; however, the slope of the stress-strain curve and thus the growth rate of the shear stress decline as the axial strain enlarges. After the sample reaches the peak stress, which happens at an axial strain of higher than 16%, 17%, and 12% for the fully weathered granite, the sandy weathered granite, and the fragmented weathered granite, respectively, the shear stress on the rock decreases with the axial strain, implying a particular strain-softening trend. 2. The stress-strain curve of the weathered granite in the saturated state is divided into two stages. Before the rock reaches its peak strength, the shear stress soars approximately linearly with the axial strain. When the weathered granite reaches its peak strength, it undergoes noticeable strain softening; in other words, the shear stress plummets with the axial strain. 3. Comparing the test results obtained in the natural and saturated states of the weathered granite reveals that the peak strength of the weathered granite decreases dramatically after exposure to water, and its corresponding peak strain is affected. 4. In actual engineering, weathered rock masses are often under deviator stress consolidation rather than isotropic consolidation. Therefore, studying the mechanical behavior of the weathered rocks under deviator stress consolidation is of more practical significance and theoretical value. The softening degree of the weathered granite varies as the consolidation mode changes and decreases to a certain extent as the shear stress applied by the deviator stress consolidation enlarges. Figure 11: The calculated stress–strain curves of the weathered granite: (**a**) Fully weathered granites; (**b**) Sandy weathered granites; (**c**) Fragmented weathered granites; (**d**) Comparison between the measured and estimated values by the proposed model in [PERSON] (2011), [PERSON] (2005), and [PERSON] (2015). 5. In the initial stages of the loading, shear shrinkage occurs since the pore water pressure increases; later, as the axial strain continues to increase, the rock shows a trend of shear dilatation until it reaches a critical state. The axial strain required for the shear stress to reach the peak value is always greater than that required for the dilatancy to occur. 6. We also established an empirical model describing the strain softening of weathered granite by utilizing the internal cohesion and the internal friction angle; the model suits weathered granite in natural and saturated states. The proposed model provides valuable guidance on describing the stress-strain characteristics of weathered granite exposed to water. However, the model developed herein is derived based on the continuous simplification of the intermediate process. Thus, there are problems such as directly treating the rock as an ideal elastic substance and ignoring the elastoplastic coupling during the rock compression. These shortcomings will be comprehensively addressed in a future study to enhance the accuracy of the model for the strain softening of weathered rock.