密粒流实验中幂律粒度分布的演变

IF 3.5 2区 地球科学 Q1 GEOSCIENCES, MULTIDISCIPLINARY
Yan Li, Wei Hu, Qiang Xu, Runqiu Huang, ChingShung Chang, Mauri McSaveney
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引用次数: 0

摘要

要理解断层和滑坡中剪切带的形成、结构和摩擦行为,尤其是在高法向应力条件下,就必须了解颗粒破碎及其导致的颗粒大小分布。三维分形维度(D3)被用来衡量颗粒大小分布和潜在的自相似性物理。先前的研究表明,根据 "约束粉碎 "模型,D3 - 2.58,或考虑到大剪切位移,D3 = 3.00。然而,来自岩崩的现场数据显示,分散的 D3 与这些预测值存在偏差,这可能是由于底层碎裂物理学(如与颗粒大小相关的碎裂概率)的偏差造成的。在此,我们进行了旋转剪切实验,以研究不同法向应力、速度和矿物成分下 D3 的演变。实验结果表明,在实验条件下,D3随剪切位移单调增加并趋近于一个极限值,它受矿物成分的影响很大,但受剪切速度和约束应力的影响较小。研究人员提出了一个修改后的大应变模型,该模型考虑了与尺寸相关的晶粒破裂概率,可以解释观察到的 D3 与之前预测值的偏差。该模型强调了致密颗粒流中颗粒破碎所涉及的复杂机制,从而导致在天然剪切区观察到的高但分散的 D3。此外,我们还认识到磨损和研磨等其他机制也会导致颗粒尺寸减小,并影响最终的分形维度。这项研究为了解剪切带中颗粒破碎的动力学提供了宝贵的见解,对理解各种地质过程具有重要意义。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
Evolution of Power-Law Particle-Size Distributions in Dense Grain-Flow Experiments

Understanding particle fragmentation and its resulting particle-size distribution is essential for comprehending shear zone formation, structure, and frictional behavior in faults and landslides, particularly at high normal stresses. 3-D fractal dimension (D3) is used as a measure of particle-size distribution, and for the potential self-similarity physics. Previous research suggests D3 – 2.58 based on the “constrained comminution” model, or D3 = 3.00 considering large shear displacement. However, field data from rock avalanches reveal scattered D3 that deviate from these predictions, possibly due to the neglection of the underlying fragmented physics, such as the particle-size-dependent fragmentation probability. Herein, we conducted rotary shear experiments to investigate the evolution of D3 under varying normal stresses, velocities, and mineral compositions. Experimental results demonstrate that D3 monotonically increases with shear displacement and converges to an ultimate value, significantly influenced by mineral composition but less affected by shear velocity and confining stress within the experimental conditions. A modified large-strain model that considered size-dependent grain-breakage probability was proposed, which may explain the observed divergence of D3 from previous predictions. This model highlights the complex mechanisms involved in particle breakage within dense grain-flows, resulting in the high but scattered D3 observed in natural shear zones. Furthermore, we recognize that additional mechanisms, such as abrasion and grinding, can contribute to the particle size reduction and influence the ultimate fractal dimension. This study provides valuable insights into the dynamics of particle fragmentation in shear zones and has implications for understanding various geological processes.

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来源期刊
Journal of Geophysical Research: Earth Surface
Journal of Geophysical Research: Earth Surface Earth and Planetary Sciences-Earth-Surface Processes
CiteScore
6.30
自引率
10.30%
发文量
162
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