## 5 Analysis and Discussion
### Analysis of Land Surface Settlement in the Engineering Construction Area
#### 5.1.2 Impact of the Development Complex  
The monitoring results in Figure 12a show that areas C3 and C4 are located in the west and south of the Dianchi International Exhibition Center, respectively, near Dianchi Lake. The vertical deformation rates in the two areas are approximately \(-13\) mm/a and \(-7\) mm/a. Figure 13a shows that residential building construction in areas C3 and C4 began after 2016 and was completed in 2018. A check of the information shows that the completion dates of the district (Shanhaihui and Yongjing Bay) were 31 December 2017, and 31 December 2018, respectively. The central coherence points of the C4 area are sparse due to the incoherence phenomenon caused by construction in 2018. According to the monitoring data in this paper, the settlement of the two plots began after the completion of construction. It is inferred that the sediment formed the stratum in a short time, with a low  
Figure 13: Changes in engineering construction in the study area from 2016 to 2021 (Google Earth image).  
degree of consolidation and large water content. Building construction leads to an increase in surface load, and strata consolidation causes the surface to settle.  
The C5 area is located in the eastern part of the Dianchi International Exhibition Center. The settlement zone in this region is relatively scattered, and the vertical deformation rate is approximately \(-9.5\) mm/a. The buildings in the area were built before 2016, and their density is high. Statistics show that there is some correlation between surface deformation and building density. If other metrics are ignored and building density is assumed to be the only criterion that represents building loads [16], then it can be inferred that high building density and thus excessive building loads eventually lead to surface settlement.  
From the monitoring results in Figure 12b, it can be seen that three main areas in the S\({}_{2}\) study area experienced settlement. The main subsidence area is located in the C6 region. The main vertical deformation rate is approximately \(-11\) mm/a, and the deformation reaches \(-23\) mm/a at the maximum. The area is mainly used for residential construction (consisting of five subdivisions), as shown in the subdivision distribution map in Figure 15. As seen in Figure 13b, the communities were completed by 2016, except for the Vanke Community, which was still under construction. The monitoring data in this paper were continued after its completion. These data show that settlement started to occur after the buildings were completed. It is possible that the ground settlement occurred due to the increased surface load caused by their construction. The rate of surface subsidence in the region decreases significantly from 2007 to 2021, as shown in Table 2 below. The deformation rate of the soil consolidation effect slows down with time. Some of the missing correlation points in the lower right corner of the C6 area are due to the construction of the sixth phase of Vanke Community. It is understood that the sixth phase of Vanke Community is under construction from 2018 until 2020. This construction occurs within the monitoring time frame of this paper; hence, there is a loss of coherence.  
Figure 14: (**a**) Kunming subway distribution map. (**b**) Location of target points along the subway. (**c**) Cumulative vertical displacements along the subway lines.