## 4 Test Results and Discussion
### Particle Breakage Characteristics
#### 4.2.5 Rolling Passes of Field Vibration Compaction  
Figure 24 shows the variations of compaction degree of different paving layer thicknesses with number of rolling passes of vibratory compaction. It can be seen from the graphs that the compaction degree increased with the increased number of rolling passes, but when compaction degree was close to about 97%, the increase slowed down. Especially in the case where the thickness of the loose paving layer was 30 cm, the compaction degree tended to decrease when the number of rolling passes was \(>\)5. However, this is not limitless, which indicates that excessive compaction may cause the degree of compaction of the thinner paving layer to decrease. This phenomenon shows that the initial vibration compaction can make the fine particles fill the voids of coarse particles and be further compacted. When the number of rolling passes of vibration compaction exceeds a certain limit, the fine particles will be further increased due to particle breakage. Thus, compacted weathered granite will show partial compaction properties similar to those of eolian sand, which has a decreased degree of compaction  
Figure 23: \(B_{r}\)-\(q/p\) (\(\varepsilon_{1}=15\%\)) curves.  
when over-compacted [28]. It can also be seen from Figure 24 that the growth rate of the degree of compaction, which increased with the number of rolling passes of vibratory compaction, slowed down with decreased thickness of the loose paving layer. As previously mentioned, in short, the thickness of loose paving layers of weathered granite filling has an obvious influence on the compaction outcome.  
In view of the characteristics of particle breakage of strongly weathered granite, the relative breakage \(B_{\rm r}\) of strongly weathered granite fillings with different thicknesses of loose paving layer (30 cm, 35 cm, and 40 cm) and numbers of rolling passes of vibration compaction were measured. The results are shown in Figure 25.  
Before compaction, three different specimens from the same roller track were selected for the sieving test. After compaction, to determine the degree of compaction of loose paving layers under a certain number of rolling passes, the average of three measurements of degree of compaction near the three points mentioned above in the same roller track was used as the degree of compaction for each number of rolling passes. The average value of relative breakage of the three points where degree of compaction was tested was calculated through sieving tests as the relative breaking \(B_{\rm r}\) under each number of rolling passes.  
As can be seen from Figure 25, with the increased number of rolling passes of vibratory compaction, the relative breakage of a given thickness of loose paving layer tended to a certain value. When the number of rolling passes was 7, the relative breakage of loose paving layers 30 cm, 35 cm, and 40 cm thick was 17.6%, 15.8%, and 13.8%, respectively. This shows that the relative breakage decreased with increased loose paving thickness. For the loose paving layer 30 cm thick, the increasing range of \(B_{\rm r}\) tended to decrease when the number of rolling passes of vibratory compaction was \(>\)4. For the loose paving layer 35 cm thick, the relative breakage began to increase by a small margin when the number of rolling passes was 5, and for the loose paving layer 40 cm thick, it was 7. It can be deduced that the number of rolling passes in the situation where the increasing trend began to slow down decreased with increased loose paving layer thickness.  
Figure 24: The relationship between degree of compaction and number of vibratory rolling passes. TLPL: thicknesses of loose paving layer.