Accurate prediction of the compression index (c_c) is essential for geotechnical infrastructure design, especially in clay-rich coastal regions. Traditional methods for determining $c_c$ are often time-consuming and inconsistent due to regional variability. This study presents an explainable ensemble learning framework for predicting the $c_c$ of clays. Using a comprehensive dataset of 1080 global samples, four key geotechnical input variables—liquid limit (LL), plasticity index (PI), initial void ratio (e₀), and natural water content w—were leveraged for accurate $c_c$ prediction. Missing data were addressed with K-Nearest Neighbors (KNN) imputation, effectively filling data gaps while preserving the dataset’s distribution characteristics. Ensemble learning techniques, including Random Forest (RF), Gradient Boosting Decision Trees (GBDT), Extreme Gradient Boosting (XGBoost), and a Stacking model, were applied. Among these, the Stacking model demonstrated the highest predictive performance with a Root Mean Squared Error (RMSE) of 0.061, a Mean Absolute Error (MAE) of 0.043, and a Coefficient of Determination ($R^2$) value of 0.848 on the test set. Model interpretability was ensured through SHapley Additive exPlanations (SHAP), with $e_0$ identified as the most influential predictor. The proposed framework significantly improves both prediction accuracy and interpretability, offering a valuable tool to enhance geotechnical design efficiency in coastal and clay-rich environments.

The drainage consolidation method can reduce porosity to consolidate soft soils. In this study, a novel siphon drainage method is used as the drainage consolidation method to lower the groundwater level. Compared to other drainage methods, the siphon drainage method is power-free, environmental-friendly, and highly efficient. Numerical simulations are conducted to verify the feasibility of the siphon drainage method on soft soil treatment. In addition, the effects of soil permeability and drainage hole spacing on its application efficiency have been studied. The results show that: (a) The siphon drainage method can accelerate the consolidation by lowering the groundwater level; (b) The larger the soil permeability is, the faster the pore water pressure decreases; (c) Adopting 1 m hole-spacing in the siphon drainage is much more efficient than methods which have a 2 m hole-spacing. In addition, the siphon drainage method is proven the effective in soft soil foundation treatment by a field test in Zhoushan, Zhejiang Province.

Marine soft soils are characterized by high compressibility, low strength, and low permeability, which often result in excessive settlement and stability problems. Drainage consolidation methods are widely regarded as effective solutions for improving such soils. This review summarizes recent progress from four perspectives: optimization of traditional techniques, combined applications of multiple methods, development of emerging innovative approaches, and advances in drainage element materials and structures. Traditional methods such as surcharge and vacuum preloading have been refined through innovations in loading schemes, drainage improvements, and design approaches, while hybrid combinations with electroosmosis, thermal treatment, and dynamic loading have further enhanced their efficiency and applicability. In parallel, novel techniques such as siphon drainage, aerosol-assisted consolidation, and osmosis-based drainage show promise for sustainable applications. Furthermore, biodegradable and multifunctional drainage elements provide new directions for environmentally friendly and efficient soft soil improvement. Looking ahead, drainage consolidation technology is expected to move toward greener, low-carbon, and intelligent solutions. This review offers a comprehensive reference for engineering practice and a useful basis for guiding future research in marine soft soil improvement.

Traditional drainage methods for marine reclamation typically consume large amounts of energy and have a negative environmental impact. The siphon-vacuum drainage method (SVD) automatically forms a vacuum and drains using less energy. It has significant potential for research and application. In this study, a theoretical model is used to calculate the vacuum formation process and drainage rate. Qualitative analysis and global sensitivity analysis were conducted to investigate the effect of various factors in the SVD on vacuum formation and drainage. The qualitative analysis suggests that modifying the length and diameter of the siphon pipe and the thickness of the sealing soil column to increase the siphon rate can improve the vacuum degree and drainage efficiency. Sobol global sensitivity analysis reveals that the sealing soil column thickness is the main factor affecting the vacuum, with a first-order sensitivity index accounting for up to 79.48%. The impact of cylinder diameter and the local resistance coefficient (0.43%) can be almost neglected. A fitting equation for estimating the maximum achievable vacuum is provided. Calculations show that the vacuum formed by the SVD can reach over 80 kPa. This work can help optimize SVD design and advance environmentally friendly marine reclamation projects.