A research team from the National & Local Joint Engineering Laboratory for Marine Mineral Resources Exploration Equipment and Safety Technology at Hunan University of Science and Technology published a paper in the journal Mining Science and Technology, titled:
"Mechanism of low-disturbance and high-pressure-retaining sampling of seafloor sediments at 10000m depth and its laboratory experiment and on-site sea trials"
The paper summarises their latest research achievements in deep-sea sediment sampling technology, including the design of a novel full-ocean-depth pressure-retaining sediment sampler, the study of low-disturbance coring mechanisms based on spherical cavity expansion theory, and the validation of sampler performance through laboratory tests using the GDS Stress Path System and sea trials.
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Paper Overview
1. Research Background
The deep-sea seafloor holds abundant resources such as oil, gas, minerals, biological materials, and sediments. Obtaining high-quality deep-sea sediment samples is of great significance for conducting geological and environmental science research. However, due to the complex structure of the deep seafloor and the varying physical and mechanical properties of different sediment lithologies, traditional sampling tools often disturb the sediments during the sampling process, compromising sample quality.
Therefore, developing a sampler that can retrieve low-disturbance, high-pressure-retaining sediment samples under extreme deep-sea conditions is of both scientific and practical value.
2. Experimental Methodology
2.1. Sampler Design
A novel full-ocean-depth pressure-retaining sediment sampler was designed. The sampler comprises a sampling unit, a pressure compensation unit, and a flushing unit. It features a self-sealing structure that maintains sample pressure during recovery, limiting pressure loss to less than 20%.
Key specifications:
- Size: 815 × 475 × 756 mm
- Weight: 160 kg
- Operating depth: 11,000 m
- Sample volume per retrieval: 230 mL
- Sampling depth: 160 mm
2.2. Theoretical Model Development
Based on the theory of spherical cavity expansion, a radial disturbance model for sediment coring was developed. It analyzes the distribution of stress and strain fields during sampling. The model combines elastoplastic theory with pore water seepage factors. The radius of plastically deformed sediment around the spherical cavity serves as an index to evaluate radial disturbance.
2.3. Laboratory Validation
A disturbance simulation platform was built to mimic the sediment coring process. The GDS stress path triaxial test system (GDSTTS) was used, with sensors embedded in the sediment to monitor radial stress and pore pressure during coring, thereby validating the theoretical model.
2.4. On-Site Sea Trials
The sampler was deployed on the Fendouzhe deep-sea submersible and tested at depths of 9298.4 m and 9142.8 m in the Kuril-Kamchatka Trench. The results showed pressure retention rates of 94.21% and 92.02%, significantly exceeding the current industry standard of 80%. The recovered samples displayed clear sedimentary layering and minimal disturbance.
3. Conclusions
3.1. Model Validation:
Laboratory results confirmed that the radial disturbance model based on spherical cavity expansion theory accurately describes stress and strain distribution during sediment sampling.
3.2. Sampler Performance:
Field trials demonstrated that the new full-ocean-depth sampler can obtain high-quality pressure-retained samples under extreme deep-sea conditions. The pressure retention rate far exceeds existing standards, and sample disturbance is minimal.
3.3. Factors Influencing Disturbance:
Cohesion and elastic modulus of sediments were identified as major influencing factors, while internal friction angle and Poisson's ratio had less impact. Reducing the wall thickness and increasing the inner diameter of the sampling tube can effectively reduce disturbance and improve sample quality.
3.4. Scientific Significance:
The newly developed sampler and low-disturbance coring technology offer strong technical support for deep-sea resource development and marine scientific research. This advancement contributes significantly to the development of China's deep-sea capabilities.
The paper in the journal Mining Science and Technology can be read here - https://doi.org/10.1016/j.ijmst.2025.06.001
