# Experimental Study on the Dynamic Response of an Immersed Tunnel Element Moored inside the Harbor
## 5 Conclusions  
In this study, the dynamic responses of an immersed element moored inside a harbor were studied by physical model tests. The wave height development process inside a harbor was determined by a wave evolution test. The influences of environmental factors, element load conditions, and mooring spacing on the dynamic response characteristics were examined. According to the research, the following conclusions can be drawn:  
1. The incident wave attenuates significantly after passing into the harbor, and it takes a period of time for the incident wave from the harbor gate to reach a relatively stable state;
2. The dynamic response characteristics of a moored, immersed element are different under different environmental load types. With the wind action, the element experiences a net sway toward the leeward side, a small amplitude oscillation occurs, and  
Figure 15: Experimental and theoretical results of an element wind load under different free-board-to-draft ratios (3 s average speed of 47.4 m/s is used and the wind drag coefficient of 1.0 is adopted for theoretical estimation).  
the wind load is borne by the windward cables. With the wave action, the motion response of an immersed element includes a high-frequency part and a low-frequency part, and the cable on both sides will be tensioned. With the combined action of both wind and wave, both the characteristics under wind action and those under wave action are reflected;
3. The dynamic response of a moored tunnel element varies with the load condition (or freeboard-to-draft ratio). With wind action, the dynamic response is positively correlated with the freeboard-to-draft ratio and reaches its maximum amplitudes under a no-load condition. With wave action, the dynamic response under half-load and no-load conditions is significantly greater than that under heavy load or full load conditions;
4. No adverse mutual interference was found when the two elements were moored simultaneously at a distance far apart at approximately one times the element length or at a near distance at approximately half the element length inside the harbor. Simultaneous mooring of multiple tunnel elements inside the harbor is a potentially feasible scheme with appropriate spacing between each other.  
Conceptualization, Q.O. and Y.H.; data curation, Y.H.; formal analysis, Y.H.; funding acquisition, S.S. and J.M.; investigation, Q.O., Y.H., S.S. and W.P.; methodology, Y.H. and J.M.; project administration, B.Y.; supervision, B.Y.; validation, C.Q. and W.P.; visualization, Q.O., Y.H. and J.M.; writing--original draft, C.Q.; writing--review and editing, Q.O. All authors have read and agreed to the published version of the manuscript.  
This research was funded by the R&D project in key areas of Guangdong Province (2019B111105002), the National Key R&D Program of China (2022 YFB2602800), and the Technology Project of Anhui Province Group Limited for Yangtze-to-Huaihe Water Diversion (Contract No. YJJH-ZX-20220705481).  
Not applicable.  
The data presented in this study are available from the corresponding author upon request.  
This physical model test was conducted in the experimental harbor basin of the Tianjin Research Institute for Water Transport Engineering.  
The authors declare no conflict of interest.