气候变化领域集成服务门户(CCPortal): Microfracture propagation in gneiss through frost wedging: insights from an experimental study

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DOI	10.1007/s11069-019-03846-3
	Microfracture propagation in gneiss through frost wedging: insights from an experimental study
	Musso Piantelli F.; Herwegh M.; Anselmetti F.S.; Waldvogel M.; Gruner U.
发表日期	2020
ISSN	0921030X
起始页码	843
结束页码	860
卷号	100 期号:2
英文摘要	Ice-driven mechanical weathering in mountainous environment is considered as an efficient process for slow but cyclical mechanical preconditioning of rockfall events. In this study, we simulate subcritical microfracture propagation under frost wedging conditions along pre-existing mechanical weaknesses of intact rock bridges with an innovative experimental approach. Two series of freeze–thaw experiments conducted in an environmental chamber were carried out to investigate and monitor the propagation of artificially induced fractures (AIF) in two twin gneiss samples. A displacement sensor recorded the sample’s in situ deformation in an environmental chamber during the experiments. 3D X-ray CT scans, performed before and after the experiments, as well as thin sections showing the post-experiment state of the deformed samples allowed tracking and quantification of fracture propagation. Our results demonstrate that frost wedging propagated the AIFs 1.25 cm2 and 3.5 cm2 after 42 and 87 freeze–thaw cycles, respectively. The experiments show that volumetric expansion of water upon freezing, cooperating with volumetric thermal expansion and contraction of the anisotropic rock, plays a key role in fracture widening and propagation. Based on these results, this study proposes that: (1) frost wedging exploits intrinsic pre-existing mechanical anisotropies of the rock; (2) the fracturing process is not continuous but alternates between stages of fast propagation and more quiet stages of stress accumulation; and (3) downward migration of “wedging grains,” stuck between the walls of the fracture, increases the tensile stress at the tip, widening and propagating the fractures with each freeze–thaw cycle. The experimental design developed in this study offers the chance to visualize and quantify the long-term efficiency of frost wedging in near-natural scenarios. © 2020, Springer Nature B.V.
关键词	Fracture propagation Frost wedging Low-porosity jointed rocks Rock bridges Wedging grains
英文关键词	anisotropy; bridge; experimental study; fracture propagation; freeze-thaw cycle; gneiss; joint; weathering
语种	英语
来源期刊	Natural Hazards
文献类型	期刊论文
条目标识符	http://gcip.llas.ac.cn/handle/2XKMVOVA/205848
作者单位	Institute of Geological Sciences, University of Bern, Baltzerstrasse 1+3, Bern, 3012, Switzerland; Kellerhals und Häfeli AG, Kapellenstrasse 22, Bern, 3011, Switzerland; Oeschger Centre for Climate Change Research, Bern, Switzerland
推荐引用方式 GB/T 7714	Musso Piantelli F.,Herwegh M.,Anselmetti F.S.,et al. Microfracture propagation in gneiss through frost wedging: insights from an experimental study[J],2020,100(2).
APA	Musso Piantelli F.,Herwegh M.,Anselmetti F.S.,Waldvogel M.,&Gruner U..(2020).Microfracture propagation in gneiss through frost wedging: insights from an experimental study.Natural Hazards,100(2).
MLA	Musso Piantelli F.,et al."Microfracture propagation in gneiss through frost wedging: insights from an experimental study".Natural Hazards 100.2(2020).