Advances in Marine Geological and Geotechnical Hazards

Since the first hearth was kindled, energy has steered human destiny, and today the ocean offers its own vast portfolio [1,2]. Along the surface, steady trade winds spin floating turbines; above, photovoltaic rafts drink in photons; within tides and swells, oscillating bodies harvest relentless mechanical power; across thermal gradients, warm and cold water drive closed-loop engines; and beneath the seabed, ancient organics have become oil, gas, and icy natural gas hydrates [3,4]. Each resource sits in a distinct physical niche, demanding tailored technologies, legal regimes, and environmental safeguards. Yet all share a common prerequisite: an intimate knowledge of the marine realm that hosts them.

Turning these gifts into usable power confronts geologic hazards that can erase decades of investment in seconds. Submarine landslides, triggered by earthquake or hydrate dissociation, can shear pipelines [5,6]; cyclic wave loading and scour undermine turbine foundations [7]; and unexpected pore pressures collapse wellbores [8]. To anticipate such threats, engineers must first characterize the seafloor soils and then understand complex interactions between the soils and structures for marine energy developments. Over the past decade, the surge in offshore renewable energy, port expansion, and deep-sea resource recovery has pushed coastal and geotechnical engineering into new frontiers. Floating wind turbines now operate in water depths exceeding 200 m; gravity-based foundations are being adapted for liquefiable seabed; and subsea pipelines cross active fault zones with unprecedented resilience [9]. These achievements, however, have also revealed gaps in our understanding of coupled hydrodynamic–geotechnical processes, from hydrate-rich sediments to cyclically loaded carbonate sands [10,11].

To capture these advances and catalyze further innovation, we have organized this Special Issue entitled “Advances in Marine Geological and Geotechnical Hazards” within the Journal of Marine Science and Engineering. For the Special Issue sixteen manuscripts were submitted for consideration, and all were subjected to a rigorous review process. In total, eleven research papers were finally accepted for publication and inclusion in this Special Issue. The contributions are listed as follows:

1.

Jiang, J.; Luo, C.; Wang, D. Numerical Simulation of Vertical Cyclic Responses of a Bucket in Over-Consolidated Clay. J. Mar. Sci. Eng. 2024, 12, 1319. https://doi.org/10.3390/jmse12081319.

2.

Gu, L.; Yang, W.; Wang, Z.; Wang, J.; Ye, G. Response of a Coral Reef Sand Foundation Densified through the Dynamic Compaction Method. J. Mar. Sci. Eng. 2024, 12, 1479. https://doi.org/10.3390/jmse12091479.

3.

Tang, X.; Xin, D.; Lei, X.; Yao, T.; Meng, Q.; Liu, Q. Large-Scale Triaxial Test on Mechanical Behavior of Coral Sand Gravel Layered Samples. J. Mar. Sci. Eng. 2024, 12, 1784. https://doi.org/10.3390/jmse12101784.

4.

Cao, L.; Zhao, H.; Yang, B.; Zhang, J.; Song, H.; Fu, X.; Liu, L. A Theoretical Model for the Hydraulic Permeability of Clayey Sediments Considering the Impact of Pore Fluid Chemistry. J. Mar. Sci. Eng. 2024, 12, 1937. https://doi.org/10.3390/jmse12111937.

5.

Yan, Y.; Liu, H.; Dai, G.; Xiang, Y.; Xu, C. Analysis of the Vertical Dynamic Response of SDCM Piles in Coastal Areas. J. Mar. Sci. Eng. 2024, 12, 1950. https://doi.org/10.3390/jmse12111950.

6.

Lei, J.; Leng, K.; Xu, W.; Wang, L.; Hu, Y.; Liu, Z. Effective Stress-Based Numerical Method for Predicting Large-Diameter Monopile Response to Various Lateral Cyclic Loadings. J. Mar. Sci. Eng. 2024, 12, 2260. https://doi.org/10.3390/jmse12122260.

7.

Liu, T.; Qing, C.; Zheng, J.; Ma, X.; Chen, J.; Liu, X. Study on the Mechanical Behavior of Fine-Grained Gassy Soil Under Different Stress Conditions. J. Mar. Sci. Eng. 2025, 13, 373. https://doi.org/10.3390/jmse13020373.

8.

Liu, T.; Liang, Y.; Peng, H.; Yu, L.; Xing, T.; Zhan, Y.; Zheng, J. Deformation Patterns and Control of Existing Tunnels Induced by Coastal Foundation Pit Excavation. J. Mar. Sci. Eng. 2025, 13, 773. https://doi.org/10.3390/jmse13040773.

9.

Deng, X.; Wang, Z.; Qin, Y.; Cao, L.; Cao, P.; Xie, Y.; Xie, Y. Experimental Study on the Reinforcement of Calcareous Sand Using Combined Microbial-Induced Carbonate Precipitation (MICP) and Festuca arundinacea Techniques. J. Mar. Sci. Eng. 2025, 13, 883. https://doi.org/10.3390/jmse13050883.

10.

Liu, T.; Zhu, L.; Zhang, Y.; Qing, C.; Zhan, Y.; Zhu, C.; Jia, J. Experimental Study on Strength Characteristics of Overconsolidated Gassy Clay. J. Mar. Sci. Eng. 2025, 13, 904. https://doi.org/10.3390/jmse13050904.

11.

Lin, P.; Li, K.; Yu, X.; Liu, T.; Yuan, X.; Li, H. Analysis of Offshore Pile–Soil Interaction Using Artificial Neural Network. J. Mar. Sci. Eng. 2025, 13, 986. https://doi.org/10.3390/jmse13050986.

Contribution 1 numerically examines vertical cyclic responses of a single suction bucket in over-consolidated clay, relevant for tripod wind-turbine foundations. An undrained cyclic accumulation model is calibrated with direct simple shear tests and implemented in finite element analyses. Simulations reproduce centrifuge experiments, showing that displacement amplitude rises logarithmically with load cycles. A parametric investigation varying skirt length to diameter from half to double reveals that shorter skirts accumulate larger displacements. A compact predictive equation anchored at a unity aspect ratio is proposed and validated for practical ranges of geometry, soil strength, interface adhesion, and cyclic amplitude.

Contribution 2 evaluates dynamic compaction for strengthening coral reef sand foundations on remote sea islands. Pilot tests were conducted in two zones using varied impact energies. The field results showed crater depths up to forty-two centimeters, an allowable bearing capacity exceeding three hundred and sixty kilopascals, and effective improvement depths of three and a half meters. Shallow plate load tests and standard penetration tests confirmed densification. Two-dimensional particle flow simulations reproduced settlement and particle breakage patterns, revealing vertical force chains and progressive crushing beneath the impact point. The study validates dynamic compaction as a practical, economical method for large-scale coral sand improvement.

Contribution 3 examines coral sand, gravel, and two layered arrangements by using large-scale triaxial and step-loading tests. All samples showed strain hardening under drained shear. Clean gravel offered the highest peak strength and bearing capacity, followed by gravel-over-sand layers, sand-over-gravel layers, and clean sand. Friction angles exceeded forty degrees for every group, while cohesion rose sharply from sand to gravel, with layered samples in between. Bulging failure concentrated in the gravel layer within composites. Step-loading p-s curves matched previous plate tests under a four hundred kilopascal confinement, confirming that placing gravel on top best enhances foundation performance in hydraulic fills.

Contribution 4 develops a new theoretical model which quantifies how pore fluid chemistry affects permeability in clayey sediments. Using electrokinetic flow theory, the model links salinity, ion mobility, surface potential, and pore size through tortuous capillary tubes. It accurately reproduces published permeability data for kaolinite, illite, smectite, and four bentonites under various salt concentrations. Sensitivity analyses reveal that permeability drops markedly only when the electric double-layer thickness approaches the pore size. During oceanic hydrate production, desalination couples with consolidation; salinity sensitivity strengthens for initially larger pores yet weakens for smaller ones.

Contribution 5 presents a rigorous theoretical framework for evaluating the vertical dynamic response of stiffened deep cement mixing piles embedded in unsaturated, viscoelastic coastal soils. Closed-form solutions for pile-head impedance are derived using elastic wave theory and a fractional-order soil model, and validated against published data. Parameter analyses reveal that reducing the core pile radius, increasing the pile length, raising soil saturation, lowering permeability, and enlarging the relaxation shear modulus markedly improve vibration resistance. Conversely, increasing the modulus of the cement–soil exterior pile harms performance, while the core pile modulus only benefits low-frequency excitation. The findings guide cost-effective design of resilient foundations for nearshore bridges and offshore energy structures.

Contribution 6 develops an effective stress-based finite element method to predict the response of large-diameter monopiles in clay under cyclic lateral loading. A bounding surface model is implemented and validated against centrifuge tests. The results show that cyclic loading causes soil stiffness degradation, permanent pile rotation, and excess pore pressure accumulation. The mean and amplitude of cyclic loads significantly influence pile behavior and pore pressure development. The method captures key soil–structure interaction mechanisms, offering insights for offshore wind turbine foundation design.

Contribution 7 investigates the mechanical behavior of fine-grained gassy soil under varied stress conditions through triaxial testing and modeling. The experiments reveal that initial pore water pressure strongly influences excess pore pressure and shear strength, with lower values enhancing strength via bubble flooding. Strength also improves under higher consolidation pressure. However, under reduced triaxial compression, both strength and pore pressure response decline.

Contribution 8 examines how coastal foundation pit excavation affects nearby shield tunnels in Qingdao’s silty clay. Using statistical, numerical, and field data, it shows excavation drives tunnels toward the pit with increasing lateral and vertical displacement. Shallower tunnels and closer clearances experience larger deformation; widening the clearance from ten to twenty-five meters cuts displacement by one-third. Thicker diaphragm walls or deeper embedment alone offer only modest tunnel protection; supplementary tunnel-side reinforcement is needed. The work provides practical guidance for safeguarding existing metro lines during coastal construction.

Contribution 9 couples microbial carbonate precipitation with tall fescue to stabilize calcareous sand from reef islands. Laboratory tests show that higher cementation concentration and more cycles sharply improve water retention yet hinder seed emergence and root elongation by densifying the matrix. Optimal treatment balances plant growth and wind resistance, achieving an almost ninety-eight percent erosion reduction at ten meters per second wind speed. The combined technique forms a mineralized surface layer and deep root anchorage, providing a low-carbon, economical alternative for slope protection in tropical maritime environments.

Contribution 10 investigates the strength and cyclic behavior of over-consolidated gassy clay through triaxial and simple shear tests combined with electron microscopy. The results show that increasing over-consolidation compresses gas bubbles, enhances dilatancy, raises shear strength, and reduces excess pore pressure. Cyclic tests reveal superior fatigue resistance compared with saturated clay, peaking at moderate over-consolidation. Microstructural analysis confirms bubble collapse and limited flooding. The findings provide essential data for modeling coastal geohazards and engineering design.

Contribution 11 compiles a global database of eighteen hundred offshore monopile tests and develops neural network models for predicting soil resistance and pile displacement. Trained networks achieve average errors below six percent, outperforming traditional curves and finite element methods by large margins. Sensitivity analyses highlight pile diameter and soil modulus as key drivers. A real project case confirms the model’s superior accuracy and efficiency, offering a practical, uncertainty-aware tool for safer, cost-effective offshore wind foundation design.

The eleven research papers converge on offshore geotechnics and renewable-energy infrastructure—monopiles, calcareous slopes, over-consolidated gassy clay, coastal excavation, microbial stabilization, and neural network prediction—addressing how complex loading governs seabed–structure interaction, stability, and reliability. The shared driver is the urgent need for low-carbon, safe, and economical foundations for offshore wind, reef construction, and subsea pipelines, while conventional empirical or simplified methods falter under variable marine environments.

Future work should establish data-physics digital twins that assimilate real-time monitoring, laboratory tests, and machine learning for live model updating. Extensions to typhoon, seismic or long-term cyclic loading, and multi-scale multiphase coupling will move from laboratory to reef scale and from short-term response to whole-life sustainable offshore geotechnical engineering.