## 4 Results and Discussion
### Lungui Highway
According to the in situ investigation, the ground water of the test area can be mainly divided into four layers: The first layer is stagnant water contained in the filled soil layer, receiving recharge from meteoric water, surface river water, and breeding ponds, and discharging by evaporation; both the second and third layer are porewater with the characteristic of pressure-bearing, contained in the fine sand layers. It receives the recharge of vertical river and lateral permeability water; the fourth ground water layer is bedrock fracture water with very low water flow, contained in three rock layers under the ground surface of the test highway. As the in situ survey shows, the shallow groundwater has a certain hydraulic connection with the surface stream, thus the groundwater level is highly affected by season. According to the hydrological materials of this area, the maximum variation of upper side groundwater level is up to 1 meter. Figure 8 demonstrates the simulated groundwater mechanical structure of this area. Aquifer is the main body of saturated rock in the shallow soft clay layer, where water can flow easily. All of aquifers are permeable. The storage of flowing water in the aquifer is greatly affected by season [38; 39]. Groundwater flows through aquifers at a rate of 50 feet or inches per century (depending on the permeability). However, regardless of the speed, water will eventually be released or left in an  
Figure 7: Time series deformation of Lungui Highway based on the seasonal model (referenced to 27 October 2014). aquire. Each aquifer has a recharge and discharge area, respectively, and the amount of water stored in the aquifer reflects the altitude of its groundwater level. If the water inrush quantity is lower than the natural displacement, the groundwater level and the storage of aquifers will decrease [40; 41]. The water level of an aquifer is usually highly sensitive to seasonal recharge, so it usually decreases in summer or in dry years [42; 43]. In summer, high temperature promotes the evaporation of flowing water in the shallow aquifer, thus leads to the decreasing of aquifer volume. In contrast, as the temperatures drop gradually in winter, the evaporation of flowing water in the shallow aquifer is suppressed, thus the subsiding decreasing phenomenon is supposed to occur. As Figure 8 shows, from June 2015, the temperature starts to drop gradually, with an accumulated decrease of 10\({}^{\circ}\)C until December. Another important reason for this seasonal deformation variation is supposed to be related to the increasing rainfall during June to December. According to the precipitation records of Fuoshan (see Figure 9), affected by the combined upper trough and bottom vortex, increasing rainfall appeared since 27 June 2015. The average rainfall amount is 127.3 mm in Fuoshan city, with 100-250 mm at 65% automatic stations recorded, and 250 mm at Shunde automatic station. Due to the increase of rainfall, both water amount in the shallow aquifer and the discharge in nearby water system are significantly increased correspondingly. With accelerated flow speed, ground water in the aquifer of soft clay expanded due to the impact of precipitation and supply from the surrounding water system, consequently inducing considerable uplift phenomena. In order to further analyze the time series variation characteristics of high coherence point deformation, three feature points A, B and C (their positions are shown in Figure 9) are selected to be analyzed. As shown in Figure 9, point A is located at the junction of Lungui Road and Junye Road. From the comparison, we can see that seasonal model results show generally periodic variation trend, with accumulated peak subsidence of -49 mm in Jun 2015 (Figure 10a). However, from June 2015 to October 2015, significant uplift of 36 mm occurred on this point. As shown in our aforementioned analysis, with the increase of rainfall, the underground water quantity increased considerably, thus inducing the uplift phenomena.