## 5 Conclusions  
The mechanical properties of granite with maximum free water absorption under different confining pressures were studied through triaxial compression tests. The failure mechanism of granite was analyzed through the macro failure characteristics and micromorphology of the granite. The main conclusions are as follows:  
1. The maximum free water absorption of this type of granite is between 0.180 and 0.204%. The free water absorption of granite changes greatly within the first 42 h, increasing from 0% to approximately 0.150%. From 306 h to 546 h, the free water absorption of the rock sample is negligible. Therefore, the water absorption test was stopped after 546 h. The P-wave velocity was between 3300 and 4900 m/s and the variation law of the P-wave velocity was basically consistent with that of water absorption. According to the water immersion test and wave velocity measurement results of the rock samples, the samples reached maximum free water absorption after 546 h.  
Figure 16: Typical microscopic morphology of oblique fracture fragments. (**a**) Step wiping and flower wiping; (**b**) Step wiping and flower wiping; (**c**) Parallel stripe pattern; (**d**) Transgranular pull flowers. 2. The differential stress-axial strain curve can be divided into the initial compaction stage, the elastic compaction stage, the plastic deformation stage before the peak, and the residual stage after the peak. With the increase in confining pressure, the initial compaction stage becomes increasingly smaller. That is, the specimen becomes increasingly dense under the action of confining pressure and with an increase in confining pressure, the plastic deformation stage before the peak becomes longer, indicating that the plasticity of the sample is obvious with the increase in confining pressure and the peak strength and peak displacement also increase with the increase in confining pressure. The elastic modulus increases significantly at the beginning and then increases slowly. The increase in confining pressure increases the strength of the rock mass. 3. When the confining pressure is in the range of 0-20 MPa, the peak axial stress of the granite with the maximum free water absorption rate is between 146.0 and 307.6 MPa and the elastic modulus is between 31.36 and 44.18 GPa. It increased linearly with confining pressure. Using the Mohr-Coulomb strength criterion, the c value of the rock was calculated to be 26.84 MPa and the \(\varphi\) value was 51\({}^{\circ}\). From the Hoek-Brown strength criterion, the strength parameter s representing the granite rock mass is 1, m is 21.42, and \(\alpha\) is 0.499. 4. Through research on the failure characteristics and fracture surface morphology of granite triaxial compression under different confining pressures, it was found that under low confining pressure conditions, the vertical fracture surface is the main one, and the inclination angle of the fracture surface gradually decreases with the increase in the confining pressure. Under medium and high confining pressures, the inclined fracture surface was dominant. 5. The microscopic morphology of the flake-like exfoliated fragments and the fracture surface showed that they were mainly tensile fractures with partial shear failures, while the inclined fracture surfaces were mainly shear failures with partial tensile failures. Under the condition of low confining pressure, the main failure mechanism is tensile failure. The inclined fracture surface is mostly generated under medium and high confining pressures, where the main failure mechanism is shear failure. Conceptualization and methodology, Y.C. ([PERSON]); validation, formal analysis, investigation, Y.Z., Y.C. ([PERSON]) and Z.L. ; Data curation, Z.H. ; writing--original draft preparation, Y.Z. and Y.C. ([PERSON]); writing--review and editing, Y.Z., Z.L. and Y.C. ([PERSON]); visualization, Y.Z. and Y.C. ([PERSON]); supervision and project administration, Y.C. ([PERSON]); funding acquisition, Y.C. ([PERSON]).