## 3 Results and Discussion
### Analysis of Vertical Compressive Static Load Test of Single Pile
#### 3.1.2 Analysis and Judgment of Test Data  
The vertical compressive ultimate bearing capacity of a single pile shall be analyzed and determined according to the following methods: (1) according to the characteristics of settlement changing with load, for steep drop curve of load-settlement (\(Q\)-\(S\)), the load value corresponding to the starting point of obvious steep drop shall be taken; (2) according to the characteristics of settlement changing with time, the load value of the previous level with obvious downward bending at the end of settlement-time logarithm curve (\(S\)-l\(gt\)) should be taken; (3) when the settlement of pile top under a certain level of load is greater than twice the settlement under the previous level of load, and the relative stability standard has not been reached within 24 h, the load value of the previous level should be taken; (4) for the slowly varying \(Q\)-\(S\) curve, the corresponding load value of (\(s=40\) mm) should be taken according to the total settlement of pile top. For the pile with \(D\) (\(D\) is the pile end diameter) greater than or equal to 800 mm, \(s\) can be taken as the load value corresponding to 0.05\(D\). When the pile length is greater than 40 m, the elastic compression of the pile body should be considered; and (5) If the above conditions are not met, the maximum loading value should be taken as the vertical compressive ultimate bearing capacity of the pile. Thus, the characteristic value of the vertical compressive bearing capacity of a single pile shall be taken as 50% of the vertical compressive ultimate bearing capacity of a single pile. According to the test results of the vertical compressive static load test of a single pile, the curves of load-settlement (\(Q\)-\(S\)), settlement-time logarithm (\(S\)-l\(gt\)), and settlement-load  
Figure 7: Field test of a vertical compressive static load of the single pile: (**a**) ballast platform; (**b**) field test; and (**c**) lifting jack and displacement sensor installation. logarithm (\(S\)-lg\(Q\)) are drawn for the selected single piles (No. 3 and No. 4), as shown in Figures 8 and 9. Figure 8: Vertical compressive static load test results of single pile No. 3: (**a**) load–settlement curve (\(Q\)-\(S\)); (**b**) settlement–time logarithm curve (\(S\)-lg\(t\)), and (**c**) settlement–load logarithm curve (\(S\)-lg\(Q\)). From Figures 8 and 9, when the test load is added to 9566 kN, it takes 120 min to observe, and could be found that the settlement is relatively stable, and the loading has reached the maximum test load, so the loading is terminated. According to the technical requirements of the Chinese standard (JGJ 106-2014), the measured data are sorted and summarized. Table 4 summarizes the vertical static load test results of a single pile. The maximum loading value of the test single pile (No. 3) test is 9566 kN, the cumulative total settlement is 15.01 mm, and there is no obvious steep drop section of the load-settlement (\(Q\)-\(S\)) curve. For single pile No. 4, the maximum loading value is 9566 kN, and the cumulative total settlement is 4.27 mm. The test result of the limit value of the vertical compressive bearing capacity of a single pile  
Figure 9: Vertical compressive static load test results of single pile No. 4: (**a**) load–settlement curve (\(Q\)-\(S\)); (**b**) settlement–time logarithm curve (\(S\)-\(\lg\)), and (**c**) settlement–load logarithm curve (\(S\)-\(\lg\)). is 9566 kN, and the test result of the characteristic value of the vertical compressive bearing capacity of a single pile is 4783 kN. There are some differences in the vertical compressive static load test.