Liu Lele, Liu Tao, Wu Chen, Bu Qingtao, Li Chengfeng, Zhang Yongchao, Wu Bisheng
Shandong Engineering Research Center of Marine Exploration and Conservation, Ocean University of China, Qingdao 266100, China.
Key Laboratory of Gas Hydrate, Ministry of Natural Resources, Qingdao Institute of Marine Geology, Qingdao 266237, China.
Rev Sci Instrum. 2024 Jul 1;95(7). doi: 10.1063/5.0188224.
Fine-grained marine sediments containing veiny and nodular gas hydrates will evolve into fine-grained gassy sediments after hydrate dissociation due to climate-driven ocean warming. The mechanical properties of the fine-grained gassy sediments are basically acquired by ocean engineering design. However, they have not been fully understood, largely due to the lack of microstructure visualization. In this paper, a new system is developed to jointly conduct x-ray computed tomography scans, oedometer tests, and seismic wave testing on a single specimen with temperature being well controlled, allowing varieties of experimental data to be acquired effectively and automatically. The results show that stress history can hardly affect the undrained stiffness of fine-grained gassy sediments, while the drained stiffness of fine-grained sediments without gas bubbles is stress history dependent. After being unloaded, many microstructure changes remain, and examples include the free gas distribution being more concentrated and the connectivity among gas bubbles becoming much better. The multi-orientation system lays the foundation for further studies on the microstructure changes and mechanical responses of fine-grained gassy sediments associated with gas hydrates.
由于气候驱动的海洋变暖导致水合物分解后，含有脉状和结核状天然气水合物的细粒海洋沉积物将演变成细粒含气沉积物。细粒含气沉积物的力学性质基本上是海洋工程设计所需要的。然而，它们尚未得到充分理解，这在很大程度上是由于缺乏微观结构可视化。本文开发了一种新系统，能够在温度得到良好控制的情况下，对单个试样联合进行x射线计算机断层扫描、固结试验和地震波测试，从而有效地自动获取各种实验数据。结果表明，应力历史对细粒含气沉积物的不排水刚度影响很小，而无气泡的细粒沉积物的排水刚度则取决于应力历史。卸载后，许多微观结构变化仍然存在，例如自由气体分布更加集中，气泡之间的连通性变得更好。这种多方向系统为进一步研究与天然气水合物相关的细粒含气沉积物的微观结构变化和力学响应奠定了基础。
