## 5 Conclusions  
This study focused on the penetration process of a hollow penetrator structure in seabed clay based on the CEL method. A finite element model was developed to simulate the interaction between the penetrator structure and the seabed clay, with a sensitivity analysis of penetration velocity. The effects of penetrator structure parameters were investigated. The main conclusions are drawn as follows:  
1. The CEL large deformation method effectively simulated the penetration processes, with the resistance of the side of the penetrator structure increasing synchronously with depth, while the resistance of the end face of the penetrator structure converged marginally.
2. The kinetic energy of the penetrator structure critically influenced soil flow, while penetration resistance and mean pressure remained almost constant under different velocity conditions. Balancing computational efficiency with simulation accuracy for penetration performance, the penetration velocity was set at 7.4 mm/s.
3. The penetrator structure with a 15\({}^{\circ}\) head angle achieved the minimal penetration resistance as depth increased progressively. This angle can be considered the optimal choice for developing a low-disturbance penetrator structure in the deep-sea environment.
4. Plastic deformation of the in situ soil primarily occurred at the end face on the penetrating head. The width of the end face on the penetrating head (\(b/D\)) was the key parameter governing the area of the interaction region. When \(S_{\text{um}}\) was small, \(b/D\) had little effect on \(F_{\text{end}}\); however, at 10 times \(S_{\text{um}}\), \(F_{\text{end}}\) showed a positive correlation with \(b/D\).
5. The decrease in L/D ratios proportionally amplified both the penetration resistance and the soil heave characteristics. The selection of the penetrator structure diameter depends not only on the penetration performance described in this study but also on the requirements for soil sample collection in mineral resource exploration missions.  
These results provide significant guidance for understanding the penetration mechanics between a hollow penetrator structure and seabed clay, as well as for optimizing the penetrator structure design. This study primarily discussed the penetration resistance exerted externally on the penetrator. However, some limitations remain: internal soil flow and the sample core will generate internal penetration resistance, affecting penetration performance; real-world conditions such as dynamic subsea condition, pore water pressure, or  
Figure 18: Soil heave at four different \(L/D\) ratios at the maximum penetration depth.  
interactions with ROV-mounted systems will cause disturbance to the seabed clay, causing non-convergence of penetration resistance. These are aspects requiring investigation in future research.  
Conceptualization, J.L. and Z.Z.; methodology, J.L., Z.Z. and J.Z.; software, Z.Z. and H.H.; validation, J.L. and Z.Z.; formal analysis, J.L. and Z.Z.; investigation, J.L. and Z.Z.; resources, H.H. and J.Z.; data curation, J.L. and Z.Z.; writing--original draft preparation, J.L. and Z.Z.; writing--review and editing, H.H. and J.Z.; visualization, J.L. and Z.Z.; supervision, J.L. and J.Z.; project administration, J.L. and J.Z.; funding acquisition, J.Z. All authors have read and agreed to the published version of the manuscript.  
This research was funded by the Science Fund for Distinguished Young Scholars of Jiangsu Province, grant number: BK20230014.  
Not applicable.  
The raw data supporting the conclusions of this article will be made available by the authors on request.  
The authors are thankful to the anonymous reviewers, whose suggestions substantially improved the quality of the article.  
The authors declare no conflicts of interest.