Microstructural evolution and mechanical behaviors of rock salt in energy storage: A molecular dynamics approach

IF 7 1区 工程技术 Q1 ENGINEERING, GEOLOGICAL International Journal of Rock Mechanics and Mining Sciences Pub Date : 2024-08-28 DOI:10.1016/j.ijrmms.2024.105882
Zhuyan Zheng , Guibin Wang , Xinyi Hu , Chengcheng Niu , Hongling Ma , Youqiang Liao , Kai Zhao , Zhen Zeng , Hang Li , Chunhe Yang
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Abstract

The microstructure of rock salt significantly influences its macroscopic mechanical behaviors and deformation phenomena. Understanding the deformation and failure characteristics of rock salt at multiple scales is crucial for the secure and efficient functioning of energy storage in salt caverns. Although the macroscopic behaviors of rock salt are well understood, the microstructural changes occurring under uniaxial compression have not been thoroughly investigated. This study aims to investigate the evolving laws of rock salt microstructure and mechanical properties during the damage process, thereby providing a fundamental understanding of the underlying mechanism. To achieve this, a series of characterization tests on rock salt were conducted to study its microstructure and defects. Building on this, molecular dynamics simulations were utilized in rock mechanics to elucidate the mechanical behaviors, structural evolutions, and dislocation motions of rock salt during the damage process. The rock salt obtained from Qianjiang, China, is a polycrystalline material with an average subgrain size of 46 nm and an average dislocation density of 4.76 × 10−6 1/Å2. Uniaxial compression of single crystal NaCl exhibits three stages: elastic compression, rapid dislocation multiplication, and forest hardening. Scattered dislocations and isolated dislocation tangles trigger further plastic slippage, leading to decreased strength. Later, the formation of a dislocation cell network hinders further slip and reinforces the strength of rock salt. Plastic deformation is found to be a dominant factor in grain refinement and the formation of polycrystalline structures. Intergranular cracking results from cross-patterned dislocation lines on grain boundaries, which become vulnerable areas of the structure. This study describes the evolutionary process of rock salt microstructures and mechanical properties, identifies the micro-destruction mechanisms during the damage process at the ionic level, and provides insights into the micro-mechanical behavior of rock salt and for the design and stability assessment of underground energy storage facilities.

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储能岩盐的微结构演变和力学行为:分子动力学方法
岩盐的微观结构对其宏观机械行为和变形现象有重大影响。了解岩盐在多个尺度上的变形和失效特征对于盐穴储能的安全和高效运行至关重要。虽然人们对岩盐的宏观行为已经有了很好的了解,但对其在单轴压缩条件下发生的微观结构变化还没有进行深入研究。本研究旨在探究岩盐微观结构和力学性能在破坏过程中的演变规律,从而从根本上了解其背后的机理。为此,我们对岩盐进行了一系列表征试验,以研究其微观结构和缺陷。在此基础上,利用岩石力学中的分子动力学模拟来阐明岩盐在损伤过程中的力学行为、结构演变和位错运动。从中国潜江获得的岩盐是一种多晶材料,平均亚晶粒尺寸为 46 nm,平均位错密度为 4.76 × 10-6 1/Å2。单晶氯化钠的单轴压缩分为三个阶段:弹性压缩、快速位错倍增和森林硬化。分散的位错和孤立的位错缠结会引发进一步的塑性滑移,导致强度下降。之后,位错单元网络的形成阻碍了进一步的滑移,并增强了岩盐的强度。研究发现,塑性变形是晶粒细化和多晶结构形成的主要因素。晶间开裂源于晶界上的交叉位错线,这些位错线成为结构的脆弱区域。本研究描述了岩盐微观结构和力学性能的演变过程,确定了离子层面破坏过程中的微观破坏机制,为岩盐的微观力学行为以及地下储能设施的设计和稳定性评估提供了见解。
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来源期刊
CiteScore
14.00
自引率
5.60%
发文量
196
审稿时长
18 weeks
期刊介绍: The International Journal of Rock Mechanics and Mining Sciences focuses on original research, new developments, site measurements, and case studies within the fields of rock mechanics and rock engineering. Serving as an international platform, it showcases high-quality papers addressing rock mechanics and the application of its principles and techniques in mining and civil engineering projects situated on or within rock masses. These projects encompass a wide range, including slopes, open-pit mines, quarries, shafts, tunnels, caverns, underground mines, metro systems, dams, hydro-electric stations, geothermal energy, petroleum engineering, and radioactive waste disposal. The journal welcomes submissions on various topics, with particular interest in theoretical advancements, analytical and numerical methods, rock testing, site investigation, and case studies.
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