## 3 Results and Discussion
### Effect of Variation in Fly Ash-Stabilized Loess on CBR  
The CBR value is an indicator of soil strength and bearing capacity. Figure 3 shows the CBR value of non-submergence and submergence conditions at different FA ratios and curing times of specimens. As shown in the figure, the CBR value increased as the curing time and FA ratio increased. Figure 2: The influence of the variation in FASL specimen on strain at different curing times under non-submergence and submergence conditions: (**a**) zero days; (**b**) 14 days; (**c**) 28 days; and (**d**) strain increasing. With the addition of FA, the CBR value increased. Such increase is suitable for the strength and bearing capacity of loess. At zero days of curing time, the CBR value significantly first increased by 57.41% with 10% FA and then significantly decreased by 48.15%-50.0% with 20% and 30% FA, respectively, compared with that of untreated loess of non-submergence samples (Figure 3). Nevertheless, this CBR value was significantly increased as curing time increased with the addition of FA from 10% to 30%, which increased by approximately 2-4 and 4-7 times in the non-amended FA at 14 and 28 days of curing time, respectively. A sharp improvement in the CBR value was found at high FA ratio (30%) treatment compared with the CBR value of pure loess (Figure 3). Similarly, the non-submerged loess and FA mixtures also caused a notable improvement in the load-bearing properties; however, the CBR value under submergence condition significantly increased for all FA treatments. The CBR value increased by approximately 3-7, 3-5, and 4-6 times at 0, 14, and 28 days of curing time, respectively, compared with that of untreated loess (Figure 3). The increase in the CBR value was consistent with the data obtained on soft soil and loess by previous authors [51; 55; 57; 71; 72; 90], who characterized FA to improve soil bearing capacity. However, previous studies have also demonstrated that the increase in CBR with the addition of FA to loess was insignificant, which implied that an alternative method must be sought [77]. However, this discrepancy might be due to the addition of FA and lime to loess by the previous authors besides the addition FA to loess as in the present study. A decrease in CBR value was observed after the addition of 25% FA in the study of [PERSON] et al. (2016). This decrease was due to the pore water filled in the flocks [72]. These results indicated that the CBR value of FASL would significantly increase when the FA ratio was increased. The improvement in loess strength in CBR due to the addition of FA was the function of loess-FA interlocking phenomena [55]. Hydraulic binder initiated the pozzolanic properties of FA, which caused the ion exchange reaction between soil particles and FA and the increase in strength properties of treated soils [78]. The submergence condition also displayed more considerable behavior than the non-submergence condition in increasing the effect of FA on CBR value. The CBR value significantly increased with the increase in curing time under non-submergence condition by approximately 2-5 and 1-5 times at 14 and 28 days of curing time, respectively, compared with the CBR value at zero days of curing time. By contrast, no significant difference in the CBR  
Figure 3: The CBR value of non-submergence and submergence conditions at different FA ratios and curing times of specimens: (**a**) zero days; (**b**) 14 days; (**c**) 28 days; and (**d**) CBR increasing. value under submergence condition was found at 14 and 28 days of curing time compared with the CBR value at zero days of curing time; specifically, the CBR values only increased by approximately 0.8-1.2 and 1.3-1.8 times, respectively (Figure 3). This result might be due to that the CBR value under submergence condition was 0.7-3.5 times higher than that under non-submergence condition at zero days of curing time (Figure 3). This result agreed with those of [PERSON] et al. (2018), who suggested that un-soaked CBR was lower than soaked CBR [90].