## 5 Conclusions and Future Work  
The rock mass parameters obtained from either laboratory examinations or on-site investigations prove insufficient in representing the dynamic variations in these parameters under the influence of complex coexistent geological conditions during practical operational phases. It is necessary to propose an effective approach for the inversion of parameters based on the displacement data from monitoring points. In this study, a PSO-XGBoost inversion model was developed to conduct sensitivity analysis and inversion of the surrounding rock parameters of the Chuxiong section in the Central Yunnan Water Diversion project. The findings can be concluded as follows.  
1. The PSO algorithm was employed to optimize the hyperparameters of the XGBoost algorithm for parameter inversion. The outcomes of the inversion process revealed that the PSO-XGBoost model achieved an exceptional accuracy, exceeding 90% in the estimation of parameters.
2. The employment of the Sobol method for global sensitivity analysis provided deep insights into the influence of various environmental and rock mass parameters on tunnel behavior. The parameter inversion process primarily focuses on rock mechanical parameters, including the elasticity modulus, Poisson ratio, cohesion, and internal friction angle.  
Figure 11: Results and comparation between computed results and monitoring data. (**a**) A crown displacement; (**b**) B–C convergence; (**c**) D–E convergence.  
3. The inversion process, informed by a Latin Hypercube Sampling (LHS) approach and 1000 parameter samples integrated into FLAC3D simulations, yielded highly accurate predictions. The confirmation of the PSO-XGBoost model's precision through cross-sectional monitoring data, with a less than 15% relative error, solidifies its value as a reliable tool in the engineering analysis and construction of soft rock tunnels.  
This study focuses on the sensitivity and inversion of rock parameters in tunnel engineering, underscoring the importance of acknowledging variational parameters' origins and the multifaceted environment impacting hydraulic tunnel operations. It underscores the necessity of assessing the interplay among environmental factors, rock materials, and tunnel safety. Crucially, accurately predicting tunnel operation displacement is vital for effective safety management. In real-world engineering, given complex geological conditions, parameters often exhibit interdependencies rather than being entirely independent. Thus, future research will increasingly prioritize sensitivity analysis and parameter inversion, taking into account their interrelationships.  
Conceptualization, Y.W. and H.W.; methodology, Y.W. and X.G.; validation, H.W.; formal analysis, Y.W.; resources, H.W.; data curation, Y.W. and X.G.; writing--original draft preparation, Y.W. and H.W.; writing--review and editing, Y.W. and H.W.; supervision, H.W. All authors have read and agreed to the published version of the manuscript.  
This research was funded by the Key Science and Technology Special Program of Yunnan Province (grant number: 202102 AF080001).  
Not applicable.  
The original contributions presented in the study are included in the article. Further inquiries can be directed to the corresponding author.  
The authors would like to thank Yunnan Dianzhong Water Diversion Engineering Co., Ltd., Kunming 65000 for providing relevant field monitoring data for the study.  
The authors declare no conflict of interest.