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SEM images of silica sand (left column) and coral sand (right column) depicting the evolution of particle damage when tests are arrested at different strains, as follows: a, b correspond to parent materials; c, d arrested at 5%; e, f arrested at 10%; g, h arrested at 20%; i, j arrested at 30% for samples with A.R. 1:1
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A series of axial loading and unloading compression tests was conducted on siliceous and calcareous sand, using a modified oedometer apparatus. Samples were prepared using aspect ratios of 6:1 and 1:1 (diameter:height) and loaded at uniform axial strain rates of 0.01 and 10%/s. Compression was arrested at various strains up to 30%, after which the...
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... divided in four equal parts. One quarter is selected to repeat this process several times until the correct sample size is obtained. Once the sample is selected and placed on the sampling holder, several images were taken at different magnifications and working distances. Silica sand and coral sand corresponding to parent materials were examined (Fig. 7a, b), as well as other samples after loading up to 5, 10, 20, and 30% strain for samples with aspect ratio of 1:1 (Fig. 7c-j). The damage in both materials is progressive. Evidence of particle damage commences in the 5-10% strain range. For coral sand, the size degradation at larger strains appears congruous to that at smaller strains. ...
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... obtained. Once the sample is selected and placed on the sampling holder, several images were taken at different magnifications and working distances. Silica sand and coral sand corresponding to parent materials were examined (Fig. 7a, b), as well as other samples after loading up to 5, 10, 20, and 30% strain for samples with aspect ratio of 1:1 (Fig. 7c-j). The damage in both materials is progressive. Evidence of particle damage commences in the 5-10% strain range. For coral sand, the size degradation at larger strains appears congruous to that at smaller strains. However, for silica sand at 20% the particles appear different from smaller strains, with a large population of fine grains ...
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... of the QicPic for particle analyses employs 2D parameters for defining particle shape. This may introduce a bias error, but said bias is smaller for rounded particles than for elongated ones. In any case, the bias would be consistent throughout the entire study, especially because both QicPic and SEM images (Figs. 6, 7) suggest that when particles fracture, daughter particles preserve a similar shape to that of the parent material. Thus, the consistent use of the QicPic should deem the bias inconsequential for qualitative analysis of the test ...
Citations
... In der Arbeit von Suescun-Florez et al. [130] wurde die Kornzertrümmerung bei axialer Kompression untersucht. Der Kornbruch setzt etwa bei 100 -150 MPa ein und bei 5 % Dehnung. ...
Das Thema der Optimierung der Rütteldruckverdichtung ist seit vielen Jahrzehnten Gegenstand der Forschung. In dieser Arbeit werden die bisher untersuchten Mechanismen und Erkenntnisse zusammengefasst. Es ergeben sich jedoch einige Fragestellungen, aus denen sich die Forschungsfragen der vorliegenden Arbeit ableiten lassen. Die meisten Erkenntnisse sind theoretischer Natur und vieles wurde in der Praxis noch nicht nachgewiesen. Aus diesem Grund wurde ein Modellversuchsstand aufgebaut, der die Rütteldruckverdichtung mit einem Modellrüttler realitätsnah abbilden kann. Die darin eingebaute Sensorik wird im Rahmen einer Parameterstudie eingesetzt, bei der Standardversuche zur Rütteldruckverdichtung mit Parametervariationen durchgeführt werden. Durch die Parameterstudie konnten einige Vermutungen, die bisher nur theoretischer Natur waren oder aus der praktischen Anwendung stammen, erstmals nachgewiesen werden. Dazu gehören ein großer Einfluss der Schwingwegamplitude auf die Verdichtung sowie ein starker Einfluss der eingestellten Verdichtungsfrequenz. Diese Parameter sollten optimiert und nicht maximiert werden, da dies die Verdichtung wieder verschlechtern kann. Darüber hinaus hat sich der Vorlaufwinkel als geeigneter Regelparameter erwiesen, da er ein reproduzierbares Verhalten in gleichen Tiefenlagen zeigt. Weiter zeigt er das Ende eines Verdichtungsschritts in der jeweiligen Tiefenlage an, wenn er einen nahezu konstanten Wert erreicht. Zudem konnte durch den Vergleich verschiedener Verdichtungsverfahren die schrittweise Verdichtung gegenüber dem Pilgerschrittverfahren und dem konstanten Ziehen als beste Methode identifiziert werden. Auf Basis der Auswertungen wurde ein neuer Regelparameter eingeführt. Mit Hilfe des Sensorphasenwinkels kann das Bewegungsverhalten des Rüttlers erfasst und ein unrundes Bewegungsverhalten erkannt werden. Des Weiteren konnte ein Einfluss der Spülmethode, des Spüldurchsatzes und der Kornzertrümmerung festgestellt werden. Eine optimierte Verdichtungskontrolle und ein optisches Verfahren zur qualitativen Bewertung der Verdichtung wurden erstmals eingesetzt. Kern der vorliegenden Arbeit ist die Optimierung der Rütteldruckverdichtung. Hierzu konnten geeignete Regelparameter identifiziert und in Form eines multikriteriellen Regelalgorithmus umgesetzt werden. Dieser wurde für das Eindringen und Heben vorgeschlagen und erstmals für die Verdichtung angewendet. Der Modellrüttler passte seine Frequenz anhand der aufgezeichneten Sensordaten an die umgebenden Bodeneigenschaften an. Die dabei verwendeten Regelparameter wurden variiert und mit Großversuchen verglichen, um Wege und Potentiale aufzuzeigen, die im Großgerät Anwendung finden sollten. Die vorliegende Arbeit legt den Grundstein, um die gewonnenen Erkenntnisse in weiteren Modellversuchen anzuwenden und die neu entstandenen Forschungsfragen zu beantworten. Dadurch kann die Rütteldruckverdichtung optimiert werden, um in Zukunft ressourcenschonender und intelligenter eingesetzt zu werden.
... The analysis of sediment texture is an important and fundamental test to achieve the classification and understand environmental processes. The textural properties (grain-size and shape) are important parameters to perform stratigraphic, palaeoenvironmental, geological studies and geotechnical engineering (Bandini et al., 2017;Zhang et al., 2017;Shang et al., 2018;Wang et al., 2019;Mattheus et al., 2020;Wei et al., 2020;Suescun-Florez et al., 2020). ...
Grain-size analysis through dynamic image analysis is a methodology that allows the conversion of images of particles with relative motion into binary images, each particle being separated and its dimensions measured individually. When compared to the classical sieving technique, this new method presents obvious advantages, allowing great savings in resources and a significant increase in productivity. Beyond the particles size, this method also allows for the complementary analysis of the grain shape, a property related to its nature and origin, being of extreme importance in any geological and geotechnical study. In this paper, the implementation and numerical validation of this method is presented, applied to particles with dimensions between 20 micra and 30 mm, using the Camsizer P4 analyser, recently acquired by the Hydrographic Institute.
... Physical characteristics include mineralogy, shape, surface roughness, and size. While the mechanical impact on grain rupture is dependent largely on the number of contact points [19] and type and rate of loading [62,63]. The number of contact points is in turn related to shape and packing density. ...
... Micro-mechanical analysis of grains subject to compressive loading offers a number of insights concerning effects of strain rate [23,60,63] and large deformations [13,52] in high vertical stresses [25,49,50] under various initial density conditions [42,61]. First, that round grains break diametrically at first and later into smaller elongated and angular fragments [86]. ...
... The effect of vertical and shear loading and particle breakage can be quantified using a Breakage Index. Various breakage indices proved to be useful for quantifying gradation changes before and after testing [11,39,63,68,77]. In this article, a simple breakage index is devised by comparing the grain sizes at specific reference diameters using a particle breakage index B x , at a specific reference diameter, such as D 50 , such that the breakage index at D 50 is B 50 , as follows: ...
Changes in particle granulometry could lead to significant changes in a soil’s behavior, making an understanding of micro-scale granulometry essential for practical applications. Changes in particle size, shape, and particle size distribution could result from a combination of applied normal and shearing stresses, which can in turn influence further response of the material. This study explored particle breakage during both compressive and shear loading under typical stresses. A deeper understanding of the phenomenon requires distinguishing broken and unbroken grains at the particle scale. Dynamic Image Analysis (DIA) was therefore employed to quantify changes in particle granulometry in two sands, a siliceous Ottawa sand and a calcareous sand known as Fiji Pink. Pre-sorted specimens having similar size, granulometry, and particle size distributions were tested using both oedometric and direct shear tests having the same aspect ratio, facilitating a direct comparison of the effects of shearing and compression on similar materials having different mineralogy. A breakage index was used for prognosis of particle breakage at key reference diameters. During oedometric tests, grain breakage was limited in both sands at stresses up to 1.2 MPa, but it increased significantly during direct shear tests. A conceptual model was proposed to explain the particle breakage mechanism during shear, at four key phase points representing (1) maximum compaction, (2) transition from compaction to dilative behavior, (3) maximum shear stress, and (4) peak test strain. In addition, a loading intensity framework was adopted to explain the relative roles of normal and shearing stresses on particle breakage. An increase of fines in soil during shearing was also observed and related to two sources: coarser grain abrasion and finer particle crushing. The vulnerability of grains with more anisotropic shapes was also observed. The loading intensity framework suggested that attrition of particle diameter could be divided into two phases, with a transitional critical loading intensity that appeared constant for each sand. For Ottawa sand, abrasion was the primary mechanism observed, causing a significant increase in Aspect Ratio (AR) and Sphericity (S) for finer grains. For Fiji sand, a transition from abrasion to attrition was noted, leading to limited sphericity decrease for the largest particles. Finer particles cushioning larger Fiji sand particles are more prone to breakage, resulting in increased AR and S. Finally, test results were used to propose a simple hyperbolic model to predict evolution of the particle size distribution during shear, for sands. The model was also verified using published data on grain evolution during shear of a different sand, not employed in its development.
... Wang et al. [30] concluded that the particle crushing strength of calcareous sand tends to decrease as the particle shape shifts from bulky to elongated and to flaky. Suescun-Florez et al. [31] tested the damage to calcareous sand during the compression phase, identifying that the effect of particle coordination number was greater than that of internal defects in particle breaking. Wang et al. [32] demonstrated that the compression modulus of calcareous silt decreased with decreasing compactness or increasing water content. ...
Calcareous sand, ubiquitous in the geotechnical makeup of the South China Sea, exhibits both compressibility and vulnerability to fragmentation when subjected to external loading, spanning a spectrum from typical to extreme conditions. This investigation aims to quantitatively assess the compression and particle breakage characteristics of calcareous sand under varied parameters, including relative density, saturation, applied loads, and loading paths, specifically focusing on sustainable geotechnical methodologies. Through a series of confined compression tests, this evaluation employed the relative breakage ratio and fractal dimension as key evaluative metrics. The results indicated that employing this integrated approach offered a more comprehensive understanding of calcareous sand breakdown mechanisms than relying on a singular particle breakage index. Furthermore, an increase in relative density can induce a transition in particle contact behavior, shifting from point-to-point interactions to face-to-face contact, thereby reducing inter-particle stress and minimizing grain breakage, particularly under loads below 200 kPa. Increasing loads exacerbated particle breakage, with finer particles predominantly initiating this process. During reloading, pore ratios across various load levels surpass those observed during initial loading, except at 1600 kPa, where a decline in pore ratio was noted, coinciding with pore water extrusion and the onset of new particle fracturing. The lubricating effect of water reduces inter-particle friction, enhancing stress concentration at particle edges and localized particle breakage, thereby increasing the presence of finer particles without significantly altering the overall structure. Notably, the influence of pore water pressure is evident during the reloading phase. These findings contribute to a refined theoretical framework for predicting coastal erosion risks and devising effective environmental protection strategies for sustainable coastal engineering practices.
... Many research works have been carried out on the mechanical properties of CCS, such as the quasi-static mechanical property (Coop, 1990;Coop and Atkinson, 1993;Porcino et al., 2008;He et al., 2021He et al., , 2022Wang et al., 2022), dynamic property and liquefaction (Hyodo et al., 1998;Coop and Qadimi, 2007;Lopez-Querol and Coop, 2012;Xiao et al., 2018;Gao and Ye, 2019;Lv et al., 2019;Ding et al., 2021), bearing capacity (Wang et al., 2009Wan et al., 2021), creep behavior (Wang and Cai, 2017;Wang et al., 2018;Cao and Ye, 2019;Ye et al., 2019) and particles breakage (Coop et al., 2004;Donohug et al., 2009;Miao and Airey, 2013;Yu, 2018;Suescun-Florez et al., 2020;Cheng and Wang, 2021;Kuang et al., 2021;Lv et al., 2021;Wang et al., 2021a;Chen et al., 2022;Zhou et al., 2022). There are also some studies on the shear modulus of coral sand under small strain condition, such as Shi et al. (2021Shi et al. ( , 2022 and Giang et al. (2017). ...
... However, the coastal zone is facing the phenomenon of continuous degradation under the long-term operation, maintenance and erosion of the ocean (Oo et al., 2022), as shown in Fig. 1. The main reason is that the main material forming the coastal zone is calcareous sand, which has an irregular shape, many internal pores, low load-bearing capacity and easy particle crushing under pressure (Xiao et al., 2016;Suescun et al., 2020;Zhu et al., 2021). Therefore, foundations in coastal zone need to be treated to improve the physical and mechanical properties of calcareous sand areas. ...
... calcareous sand under different compactnesses and vertical stresses, establishing the connections among input work, particle breakage ratio, compactness, and vertical stress. Suescun-Florez et al. [14] assessed the damage to calcareous sand during compression and pointed out that the effect of particle coordination number was greater than that of internal defects in the particle breakage process. Shen et al. [15] found that the compressibility of calcareous sand was about 60-160 % higher than that of quartz sand under the same gradation and compactness. ...
... Figure 9 shows the initial mass fractions of particle groups A, B, and C. From Fig. 9, it can be seen that the mass fraction of particle group A decreased significantly with increasing C u , whereas that of particle group B increased with increasing C u and that of particle group C remained unchanged. For CGS-1, the massive distribution J o u r n a l P r e -p r o o f Journal Pre-proof of particle group A effectively protected the easily breakable particle groups B and C [14]. That is, under vertical stress, the presence of particle group A delayed the failure of the load-bearing structure, as manifested by the backward movement of the yield point. ...
... Under low stress, there is a larger space available for the relative motion of particles, and the corresponding vertical displacement is larger, while E s is smaller. The research results of Suescun-Florez et al. [14] and Karimpour-Fard et al. [53] have confirmed this viewpoint. ...
... However, the coastal zone is facing the phenomenon of continuous degradation under the long-term operation, maintenance and erosion of the ocean (Oo et al., 2022), as shown in Fig. 1. The main reason is that the main material forming the coastal zone is calcareous sand, which has an irregular shape, many internal pores, low load-bearing capacity and easy particle crushing under pressure (Xiao et al., 2016;Suescun et al., 2020;Zhu et al., 2021). Therefore, foundations in coastal zone need to be treated to improve the physical and mechanical properties of calcareous sand areas. ...
... Many experimental studies have already examined the effect of initial void ratio [5], particle size [6][7][8] and angularity [9][10][11], relative density [12,13], material composition [14,15], and saturation degree [16][17][18] on particle crushing and thus on soils' behavior [19]. The studies of the behavior of sand media at low to intermediate levels of stress are plentiful, but are limited for compression tests at high levels of stress (some tens to some hundreds of MPa). ...
... Similarly, Huang et al. [32] introduced yield stress as critical stress and the linear slope as the compressibility index of granular materials. The previous literature on one-dimensional compression tests on samples of silica sand has shown that smaller particles reach the yield point at stresses higher than large particles, i.e., the yield stress decreases as particle size increases [5]. Therefore, the strength of a single particle increases as particle size decreases, which is not the case in the current study; as seen in the curves, the yield stress of the large particles is higher than the small ones, with a more obvious change in the slope. ...
... This difference in the behavior of both sands has been attributed to the angular shape of GLAG particles and their weaker mineralogical constitution. Suescun-Florez et al. [5] reported that silica sand shows a considerable grain breakage beyond 10% strain, which barely depends on the compression rate. However, calcareous sand discloses a totally different behavior as the particles start to split much earlier (5% of strain), with a high compression rate dependency. ...
This work aimed to understand the mechanical behavior of siliceous and calcareous sand materials under uniaxial confined compression loading at high stress levels. For this purpose, a series of quasi-oedometric compression tests were conducted on sand materials, to examine the effects of grain size, nature, and moisture contents on the soil crushability and the compression behavior, using an upgraded thick pressure vessel device that can reach mean stress up to 500 MPa. All samples were prepared using an aspect ratio of 1:1 (diameter: height), placed inside a high strength steel vessel, and compressed at a uniform axial displacement rate of 5 µm/s. The vessel is instrumented with multiple strain gauges allowing for the characterization of the hydrostatic and deviatoric behavior of each test. The results of quasi-oedometric tests, conducted on these types of sand, up to a passive confinement of 500 MPa, show that particle breakage is enhanced by the presence of water. It was noticed that, for siliceous sand, smaller particles break more than larger particles, and that the calcareous grains manifest a rapid response to axial stress compared to siliceous sand. Testing various soil properties shows a great potential to better characterize the sensitivity to breakage of soils. Lastly, a post-mortem analysis of samples before and after testing, using the X-ray micro-tomography technique, was applied to study the mechanical damage of sand specimens.
... In recent years, image analysis (IA) of grain size and morphology has been increasingly applied in geotechnical engineering, e.g., [1,[22][23][24][25][26][27][28]. IA can generate both grain size and shape distributions and provide a quantitative statistical description for them by digitizing the outlines of grains using photography [29]. ...
The shape and the size of grains in sediments and soils have a significant influence on their engineering properties. Image analysis of grain shape and size has been increasingly applied in geotechnical engineering to provide a quantitative statistical description for grain morphologies. The statistic robustness and the era of big data in geotechnical engineering require the quick and efficient acquirement of large data sets of grain morphologies. In the past publications, some semi-automation algorithms in extracting grains from images may cost tens of minutes. With the rapid development of deep learning networks applied to earth sciences, we develop UNetGE software that is based on the U-Net architecture—a fully convolutional network—to recognize and segregate grains from the matrix using the electron and optical microphotographs of rock and soil thin sections or the photographs of their hand specimen and outcrops. Resultantly, it shows that UNetGE can extract approximately 300~1300 grains in a few seconds to a few minutes and provide their morphologic parameters, which will ably assist with analyses on the engineering properties of sediments and soils (e.g., permeability, strength, and expansivity) and their hydraulic characteristics.
