Fractal analysis of cracking in a clayey soil under freeze–thaw cycles

Lu, Yang; Liu, Sihong; Weng, Liping; Wang, Liujiang; Li, Zhuo; Xu, Lei

doi:10.1016/j.enggeo.2016.04.023

Cited by 146 publications

(55 citation statements)

References 53 publications

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“…These conditions are very general, and apply to both the drying clay experiments and polygonal terrain. More recent freeze-thaw experiments in clays also capture a similar process [152]. Furthermore, a related situation is seen in crack patterns in some gypsum sand dunes, where moisture cycles stress a surface layer of weakly concreted sand.…”

Section: Permafrost and Evolving Mud Cracksmentioning

confidence: 70%

Drying colloidal systems: Laboratory models for a wide range of applications

et al. 2018

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Abstract. The drying of complex fluids provides a powerful insight into phenomena that take place on time and length scales not normally accessible. An important feature of complex fluids, colloidal dispersions and polymer solutions is their high sensitivity to weak external actions. Thus, the drying of complex fluids involves a large number of physical and chemical processes. The scope of this review is the capacity to tune such systems to reproduce and explore specific properties in a physics laboratory. A wide variety of systems are presented, ranging from functional coatings, food science, cosmetology, medical diagnostics and forensics to geophysics and art.

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Section: Permafrost and Evolving Mud Cracksmentioning

confidence: 70%

Drying colloidal systems: Laboratory models for a wide range of applications

et al. 2018

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“…a cracked dry riverbed) also applies in the context of their kinetics. For example, Lu et al .’s () study of clay under freeze‐thaw cycles showed that the development of new, interconnected polygonal networks of cracks reached a point of stabilization, after which the main damage phenomenon observable was their widening.…”

Section: Resultsmentioning

confidence: 99%

Three‐dimensional damage morphologies of thermomechanically deformed sintered nanosilver die attachments for power electronics modules

Agyakwa

Dai

et al. 2019

Journal of Microscopy

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Summary A time‐lapse study of thermomechanical fatigue damage has been undertaken using three‐dimensional X‐ray computer tomography. Morphologies were extracted from tomography data and integrated with data from microscopy modalities at different resolution levels. This enables contextualization of some of the fine‐scale properties which underpin the large‐scale damage observed via tomography. Lateral views of crack development are presented, which show networks analogous to mud‐cracks. Crack fronts which develop in the most porous regions within the sintered attachment layer travel across the boundary into the copper substrate. The propagation characteristics of these cracks within the substrate are analysed. Evidence is provided of heterogeneous densification within the sintered joint under power cycling, and this is shown to play a major role in driving the initiation and propagation of the cracks. Examination of the texture (differing levels of X‐ray absorption) of virtual cross‐sectional images reveals the origins of the nonuniformity of densification. Finally, cracks within the sintered joint are shown to have a negligible impact on the conduction pathway of the joint due to their aspect ratio and orientation with respect to the assembly. Lay Description This paper concerns the use of three‐dimensional (3D) X‐ray tomography, a nondestructive technique, to perform cradle‐to‐grave studies of sintered nanosilver die‐attachments under operation. Sintered nanosilver die‐attachments have been proposed as a more reliable and environmentally friendly alternative to solder alloy joints for emerging power electronics module designs. However, their degradation mechanisms are not as well understood. This same sample‐study is about observing how the fine‐scale structure of a sintered attachment evolves and degrades over time. Using 3D tomography affords otherwise infeasible perspectives, such as virtual cross‐sections in the lateral plane of the attachment. These perspectives provide qualitative information which elucidates the degradation mechanisms. They demonstrate, for example, that the structure of the sintered attachment densifies under operation, and a consequence of this is the formation of shrinkage cracks in the most porous regions, much like mud‐cracks. Other imaging techniques (metallographic etching and scanning electron microscopy) have been used in correlation with 3D renderings of these cracks to analyse their propagation and reveal their relationship both with the internal structure of the sintered attachment itself, and the structure of the substrate to which it is joined. It is shown that the cracks develop within the sintered attachment layer and eventually cross over into the substrate. A comparison of two sintered attachments with contrasting bulk porosities allows the effect of initial bond quality on crack development to be examined.

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“…This assumption seems reasonable as karst soils usually have a high clay content (Blume et al, 2010;Clapp and Hornberger, 1978). However, clayey soil typically presents cracks (Lu et al, 2016); therefore, when the soil reaches saturation, preferential flow starts to occur in the soil cracks, which causes all saturation excess to quickly infiltrate to the epikarst. Just as in VarKarst, such preferential vertical flow is represented by the variable R epi,i (t) (used in Eq.…”

Section: Soil Water Balancementioning

confidence: 99%

V2Karst V1.1: a parsimonious large-scale integrated vegetation–recharge model to simulate the impact of climate and land cover change in karst regions

et al. 2018

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Karst aquifers are an important source of drinking water in many regions of the world. Karst areas are highly permeable and produce large amounts of groundwater recharge, while surface runoff is often negligible. As a result, recharge in these systems may have a different sensitivity to climate and land cover changes than in other less permeable systems. However, little is known about the combined impact of climate and land cover changes in karst areas at large scales. In particular, the representation of land cover, and its controls on evapotranspiration, has been very limited in previous karst hydrological models. In this study, we address this gap (1) by introducing the first large-scale hydrological model including an explicit representation of both karst and land cover properties, and (2) by providing an indepth analysis of the model's recharge production behaviour. To achieve these aims, we replace the empirical approach to evapotranspiration estimation of a previous large-scale karst recharge model (VarKarst) with an explicit, mechanistic and parsimonious approach in the new model (V2Karst V1.1). We demonstrate the plausibility of V2Karst simulations at four carbonate rock FLUXNET sites by assessing the model's ability to reproduce observed evapotranspiration and soil moisture patterns and by showing that the controlling modelled processes are in line with expectations. Additional virtual experiments with synthetic input data systematically explore the sensitivities of recharge to precipitation characteristics (overall amount and temporal distribution) and land cover properties. This approach confirms that these sensitivities agree with expectations and provides first insights into the potential impacts of future change. V2Karst is the first model that enables the study of the joint impacts of large-scale land cover and climate changes on groundwater recharge in karst regions.

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Fractal analysis of cracking in a clayey soil under freeze–thaw cycles

Cited by 146 publications

References 53 publications

Drying colloidal systems: Laboratory models for a wide range of applications

Drying colloidal systems: Laboratory models for a wide range of applications

Three‐dimensional damage morphologies of thermomechanically deformed sintered nanosilver die attachments for power electronics modules

V2Karst V1.1: a parsimonious large-scale integrated vegetation–recharge model to simulate the impact of climate and land cover change in karst regions

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