## 1 Introduction  
With the improvement of the economic level and the continuous development of shield technology, large-diameter slurry pressure balance shielding, with the properties of high construction quality and efficiency, has gradually become the preferred method for domestic underwater tunnel construction. Figure 1 shows the current construction status of cross-river/sea tunnels with a shield diameter of more than 10 m in operation and under construction in China [1]. It is obvious that the construction of cross-river/sea tunnels using the large-diameter shield method in China exhibits a trend of sharp increase [2]. Large-diameter tunnels are more sensitive to the ground impact than small-diameter tunnels due to the former possessing a larger cross-section [3], more segments, and more joints. The upper-soft and lower-hard strata show an obvious rock-soil stratification interface, and there are large differences in the properties between rock and soil. When the shield tunneling crosses through this type of formation, it is extremely likely to cause abnormal deformation of the excavation surface, resulting in the significant deformation of the surface [4]. An increase in the difficulty of shield construction may occur with constructions in this stratum, which will affect the construction process [5]. The embankment is an important barrier for the urban flood control system. Once the embankment is damaged, the safety of people and surrounding buildings will be seriously threatened. During the construction of an underwater tunnel using the shield method, it will inevitably cross the embankments on both sides of the river. Therefore, it is of extraordinary significance to study the deformation characteristics of the embankment and to take measures in advance to ensure the safety of the embankment. Scholars at home and abroad have recently carried out a great deal of systematic research in related fields, and it has greatly promoted the development of large-diameter shield tunnel crossing engineering construction technology under complex geological conditions. For tunnel excavation in upper-soft and lower-hard strata, [PERSON] et al. [6] comprehensively analyzed, with the help of on-site real-time monitoring and measurement methods, the evolution law of four types of multisource settlement data of surface, lining, box culvert, and pipeline in the process of shield tunneling in the upper-soft and lower-hard strata of a subway tunnel in a city. The influence of the variation of upper-soft and lower-hard strata on the stability of the surrounding rock was investigated by [PERSON] et al. [7] based on indoor physical model tests. As for large-diameter shield tunnels, [PERSON] et al. [8] obtained the calculation formula for the formation deformation caused by large-diameter slurry pressure balance shield construction based on the Mindlin solution. For tunnels crossing embankments, [PERSON] et al. [9] proposed a new method for adjusting the excessive uplifting of a shield machine, and the maximum uplifting of 118 mm was corrected via the technique of under-excavation. Based on the engineering background of Nanjing Weisan Road Crossing River Tunnel, the ABAQUS numerical method was used by [PERSON] and [PERSON] [10] to investigate the characteristics of the stratum deformation and surface settlement caused by the crossing of the flood control embankment in the Weisan Road Crossing River Tunnel in Nanjing City. According to the studies of [PERSON] et al. [11] and [PERSON] et al. [12], the three-dimensional numerical simulation method is adopted to analyze the dynamic settlement characteristics of an embankment when a large-diameter slurry pressure shield tunnel passes through the embankment of the Yangtze River. On the basis of a large amount of data obtained from on-site monitoring, [PERSON] et al. [13] adopted finite element analysis to calculate the bounds of the support pressure required for tunnel face stability, and the influences of friction angle, tunnel cover-to-diameter ratio, and water level were investigated.