# Prediction of Unconfined Compressive Strength in Cement-Treated Soils: A Machine Learning Approach
## 3 Results and Discussion
### Experimental Test Results
#### 3.1.4 Effect of Compaction Rate  
The effect of compaction rate on UCS development was examined by comparing median UCS values across the three different compaction velocities (0.75, 1.0, and 1.25 mm/min) for each combination of cement content and curing period. Figure 7 presents a multi-panel boxplot visualization of these comparisons, with each panel representing a specific combination of cement content and curing time. Figure 7: Effect of compaction rate on UCS values for cement-treated soil across cement contents (increasing top-to-bottom) and curing times (increasing left-to-right). The red circles indicate statistical outliers, defined as values falling outside 1.5 times the interquartile range from the box edges. The detailed analysis of median UCS values across different compaction rates reveals interesting patterns. While the impact of compaction rate appears less dominant than cement content and curing period, the relative differences between compaction rates were not entirely negligible for certain combinations. For most cement content and curing time combinations, the relative differences between median UCS values at different compaction rates ranged from approximately 1% to 9%. However, several combinations exhibited more substantial variations. For specimens with 5% cement after 1 day of curing, the relative difference between compaction rates of 0.75 mm/min and 1.0 mm/min reached approximately 20%, with the higher compaction rate producing greater strength. Similarly, for 5% cement specimens cured for 28 days, the difference between compaction rates of 1.0 mm/min and 1.25 mm/min was also around 20%, though in this case, the lower compaction rate yielded higher strength. For 10% cement specimens after 1 day of curing, the difference between compaction rates of 1.0 mm/min and 1.25 mm/min was roughly 15%, with the higher compaction rate producing greater strength. These more pronounced differences were primarily observed at either very early curing times (1 day) or relatively high cement contents (10%), suggesting that compaction rate may have a more noticeable effect under specific conditions. At early curing times, the soil-cement mixture is still developing its initial structure, and the rate of compaction might influence particle rearrangement and initial cement hydration. For higher cement contents, the greater quantity of cementitious material may make the mixture more sensitive to compaction procedures. However, it is important to note that no consistent pattern emerged across all combinations. The relationship between compaction rate and UCS did not follow a uniform trend, with some cases showing higher strength at increased compaction rates and others showing the opposite. For many combinations, particularly at intermediate curing periods (7 to 14 days), the differences were relatively modest (typically below 5%). These observations should be interpreted within the specific context of this experimental program, which utilized a particular soil type and a relatively narrow range of compaction velocities. Furthermore, all specimens were compacted to the same target density regardless of compaction rate, which likely contributed to the generally modest differences in strength outcomes for most combinations. From a practical perspective, these findings suggest that while compaction rate may not be the dominant factor governing UCS development in cement-stabilized soils, it can still influence strength characteristics under specific conditions, particularly during early curing or at higher cement contents. For routine applications with intermediate cement contents (5-7.5%) and standard curing periods (7-28 days), the influence of compaction rate variations within the studied range appears generally limited (typically less than 7% difference).