## 5 Conclusions  
The weathering process of in-situ granite and the particle breakage characteristics of compacted weathered granite were investigated with a series of laboratory and field tests: X-ray diffraction, sieving, heavy compaction, large-scale triaxial, and field compaction tests. In view of the aforementioned results, the following conclusions can be summarized:  
1. A preliminary relationship between weathering process parameters (\(m\) and \(r\)) and burying depth (\(h\)) is established to improve the understanding of weathering process and degree of rock by using previous grading equation. With an increase in burying depth of weathered granite, the geological year's parameter (\(m\)) decrease by power function, but the geometric progression constants (\(r\)) increase by power function. The exponent of power function in this research can be used to evaluate the weathering process of weathered granite. 2. After the heavy compaction test for samples with difference \(C_{u}\) were carried out, The uniformity coefficient \(C_{u}\) can be used to effectively reflect the influence of particle size distribution on soil particle breakage characteristics. The reasonable particle size distribution (e.g., intergranular locking structure) can reduce the potential of particle breakage of coarse-grained soil similar to weathered granite and improve the stability of subgrade filled with coarse-grained soil. 3. Because different minerals have different strength and hardness, the mineral composition and content in weathered granite have a significant effect on the particle breakage characteristics of compacted weathered granite. This provides a relatively reliable reference for selecting high-strength and durable subgrade fillings. 4. The compaction effect during embankment compaction has a significant effect on the particle breakage properties of weathered granite. With the further increase of compaction effect, \(B_{r}\) will tend toward a certain limit value. 5. At the lower stress level, the compacted weathered granite shows obvious particle breakage characteristics. There is a significant positive correlation between stress level and particle breakage. Under the same axial strain (e.g., 15%), the higher confining pressure promotes strain confinement and results in further particle breakage of compacted rock samples. 6. The thickness of loose paving layers and the number of rolling passes obviously affect the particle breakage characteristics of weathered granite fillings. Excessive compaction may lead to a slight decrease in the degree of compaction of embankment, which road engineers should pay attention to. Before the subgrade is formally filled with weathered granite, the subgrade test section should be paved in order to determine the best mechanical assembly, reasonable construction technology, and reliable quality-control measures, and to prevent over-compaction from a decrease in the degree of compaction, affecting the overall stability of the subgrade. Figure 25: The relationship between relative breakage and number of vibratory rolling passes. Given that wet conditions may influence the evolution of embankments after construction, future extensive research should be focused on dynamic measurement methods of particle breakage and long-term behavior degradation analysis of subgrade as a result of further weathering and particle breakage [29; 30; 31]. Analyzing the weathering mechanism and particle breakage characteristics of rock by using fracture mechanics is still a challenging task, so researchers and engineers should pay more attention to the weathering mechanism of granite by means of fracture mechanics and micromechanics and evaluate the stability and safety of the subgrade filled with weathered granite by using safe rock theory in the future. [PERSON] and [PERSON] conceived and designed the experimental scheme and writing structure of this paper. The all lab experiments in this research were performed by [PERSON] and [PERSON]. [PERSON] wrote this manuscript.