Rock avalanche deposits store quantitative evidence on internal shear during runout
Rock avalanche deposits store quantitative evidence on internal shear during runout
复制标题
岩石雪崩沉积物存储了跳动期间内部剪切的定量证据
DOI：
10.1002/2017gl073774
复制
发表时间：
2017
影响因子：
5.2
通讯作者：
McSaveney M. J.
中科院分区：
文献类型：
--
作者：
Zhang M.;McSaveney M. J.
通过38个不同法向应力、剪切应变和剪切应变速率的环剪试验，研究了内剪对岩石雪崩冲击过程中颗粒破碎的定量影响。我们比较了剪切前后样品的粒度特征。随着法向应力和剪切应变的增大，晶粒尺寸减小。晶粒尺寸的减小是通过在应变过程中与强力链中的晶粒相互作用相关的晶粒断裂来推断的。这一结果与深部岩石雪崩暴露的逆级配结构以及随着岩石雪崩移动距离的增加颗粒的细化和级配一致。我们的研究表明，通过适当的校准，岩石雪崩沉积物中粒度分布的变化可以提供内部剪切在其跳动期间分布的定量信息。
We investigated the quantitative effect of internal shear on grain breakage during rock avalanche runout, by means of 38 ring‐shear experiments on identical sand samples at different normal stresses, shear strains and shear strain rates. We compared sample grain‐size characteristics before and after shearing. We found that grain size decreased with increase in normal stress and shear strain. Reduction in grain size was inferred to occur through grain breakage associated with grain interactions in strong force chains during strain. The results were consistent with observations of both inverse‐grading structure in deep rock avalanche exposures, and fining and grading of particles with increasing rock avalanche travel distance. Our study suggested that with appropriate calibration, variations in grain‐size distributions within a rock avalanche deposit would provide quantitative information on the distribution of internal shear during its runout.