Large Gravel Research Articles

The gravel fans of upper Glen Roy, Lochaber, Scotland: their importance for understanding glacial, proglacial and glaciolacustrine dynamics during the Younger Dryas cold period in an Atlantic margin setting

Over the past 200 years significant research effort has gone into explaining the origin of the obvious former shorelines in Glen Roy (the so-called “Parallel Roads”). The large gravel deposit at the mouth of Glen Turret has attracted similar interest, but a solution to its origin and age remains contested: the same applies to the associated gravel fans in upper Glen Roy. This paper presents the results of systematic mapping and instrumental levelling of these features and new evidence from two previously unrecorded gravel fans in the nearby Allt Chonnal valley. Interpretation of altitudinal and lithofacies data indicates that all the fans (including the one at the mouth of Glen Turret) were deposited in a series of ice-dammed lakes during the Loch Lomond Stadial (Younger Dryas). The largest gravel fans were deposited in the shallow lake heads of the 260m, 325m and 350m lakes in upper Glen Roy, infilling these areas to the extent that deposition was in part subaerial. The absence of foreset bedding from the deposits is explained by the relatively shallow depth of lake waters, which inhibited development of classic Gilbert-type deltas and encouraged Hjulström-type fans. The previous assumption that gravel deposition into the 325m and 350m lakes was relatively limited is shown to be erroneous. The Allt Chonnal gravel fans, deposited into these lakes, have an estimated combined volume of 6,000,000m3 deposited in about 200 years. Significant gravel deposition into these former lakes continued at least until glaciers started to retreat in Glen Roy. When glacier retreat began, gravel deposition was reduced by over 85%. This research also concludes that the glacier which deposited the Turret fan emanated from Glen Gloy, supplied not only by ice from the south but also from ice that spilled into Glen Gloy from the adjacent Great Glen. The Loch Lomond Stadial (LLS) ice cap mapped in the Monadhliath Mountains was connected to the west Highland ice cap, which at the time filled the Great Glen. Regional equilibrium line altitude (ELA) estimates, based solely on the Monadhliath LLS ice cap evidence, may therefore be altitudinally too high.

Passive acoustic monitoring of bed load discharge in a large gravel bed river

AbstractSurrogate technologies to monitor bed load discharge have been developed to supplement and ultimately take over traditional direct methods. Our research deals with passive acoustic monitoring of bed load flux using a hydrophone continuously deployed near a river bed. This passive acoustic technology senses any acoustic waves propagated in the river environment and particularly the sound due to interparticle collisions emitted during bed load movement. A data set has been acquired in the large Alpine gravel‐bedded Drau River. Analysis of the short‐term frequency response of acoustic signals allows us to determine the origin of recorded noises and to consider their frequency variations. Results are compared with ancillary field data of water depth and bed load transport inferred from the signals of a geophone array. Hydrophone and geophone signals are well correlated. Thanks to the large network of deployed geophones, analysis of the spatial resolution of hydrophone measurements shows that the sensor is sensitive to bed load motion not only locally but over distances of 5–10 m (10–20% of river width). Our results are promising in terms of the potential use of hydrophones for monitoring bed load transport in large gravel bed rivers: acoustic signals represent a large river bed area, rather than being local; hydrophones can be installed in large floods; they can be deployed at a low cost and provide continuous monitoring at high temporal resolution.

Experimental and numerical investigation of density current over macro-roughness

The dynamics of density current over a bottom covered by macro-roughness elements were investigated by laboratory experiments and a computational model using large eddy simulations. The macro-roughness considered had significant size in comparison with the scale of density current. Five different roughness conditions were considered, namely flat bottom (for reference), half spheres, fine gravels, medium gravels, and large gravels. These bottom conditions had variations in roughness element size, shape, angularity, and spatial configuration. The density current was a lock-exchange type with a density difference of 1% between the two fluids initially separated by a gate in the middle. In the computational model, the roughness was captured using two different methods depending on the size of the roughness elements. For the large roughness elements, i.e., the half spheres and the medium and large gravels, an immersed boundary method was used to resolve the surface of each gravel, which was obtained through 3D laser scanning. The realistic and physically correct placement of these scanned objects in the simulation domain was achieved using a computer tool which can detect the collision of rigid bodies and simulate their dynamics. For the fine gravels, a rough wall function was used. The computational model was validated with the data measured in the experiments, including front position and velocity, and point velocity measurement within the current. The results show that density currents over macro-roughness have distinct behavior from those over a smooth boundary. The characteristics (size, angularity, and pavement pattern) of the macro-roughness play a key role in the current development. Macro-roughness significantly retards the front propagation and enhances entrainment.

Characterization of gravelly alluvium

Characterizing project sites where gravelly alluvium is present poses particular challenges. Conventional field and laboratory techniques are significantly limited when large gravel particles either prevent their operation or adversely influence their measurements. The deposition of gravelly alluvium often involves complex, energy and sediment load dependent processes that can result in highly spatially variable deposits comprised of gravel to clay sized particles. This pervasive variability warrants an integrated site characterization approach anchored in an understanding of the geological formation processes and the expected controlling deformation/failure mechanisms, confirmed by the site investigation, simplified as part of site idealization, and verified during construction and long term monitoring. Systematic incorporation and handling of the site variability during the site idealization process is particularly important. Recent work at several gravelly alluvial sites has allowed the development of new approaches and techniques for improved site characterization. In particular, the benefit of continuous sonic sampling is demonstrated and a systematic method for evaluating gravel influence on SPT N values is outlined. Finally, an overview of the instrumented Becker Penetration Test (iBPT), a closed-ended, large diameter penetrometer with new direct energy measurement at the drill string tip is presented.

Prediction of Wellbore Stability in Conglomerate Formation Using Discrete Element Method

Wellbore collapse and drilling fluid leakage are prone to occur when drilling a conglomerate formation. The conventional method for predicting wellbore stability cannot achieve sufficient accuracy when used in conglomerate formations. In this study, the particle size distribution in the conglomerate formation is characterized by the statistics of particle size analysis. Based on microstructure analysis and laboratory tri-axial tests, physical and mechanical properties of conglomerate can be obtained. Discrete element method, by particle flow code software $$\hbox {PFC}^{2\mathrm{D}}$$ , is applied to simulate the failure process of the conglomerate formation near the borehole region and investigate the influence of gravel size distribution, drilling mud density and fluid infiltration on the severity of wellbore instability. The simulation results show that the process of wellbore instability within the conglomerate formation correlates with the particle size of the gravels and their spatial distribution: in the fine-grained conglomerate formation, the cracks dominantly extend toward the direction of maximum horizontal stress; in the coarse-grained conglomerate formation, the cracks initially generate around large gravels and preferentially extend toward the gravel-concentrated zone. In addition, the variation of drilling mud density substantially affects the number of cracks in terms of mechanical analysis. The favorable mud density for specific conglomerate formation is found to minimize crack numbers. Further, while considering fluid infiltration into formation, more cracks should be accounted and worse instability state is reached in comparison with counterpart without infiltration. In this sense, practical operations are recommended to allow for the pressure equilibrium and sealing capability of drilling fluid.

Turbulence in a Gravel-Bed Stream with an Array of Large Gravel Obstacles

AbstractThis experimental and analytical study investigates the double-averaged (DA) turbulent flow characteristics within an array of large gravel obstacles found atop a porous gravel bed. Analysis of the experimental data reveals that the DA streamwise velocity preserves the logarithmic law above the form-induced sublayer, while a linear law and a third-degree polynomial function apply within the form-induced and interfacial sublayers, respectively. The form-induced shear stress is 70% of the DA Reynolds shear stress (RSS) occurring at the virtual bed level. The DA turbulent kinetic energy (TKE) components, streamwise and vertical, attain their peak values at the obstacle crest level, while they diminish sharply below the virtual bed level. The fluxes of the TKE streamwise and vertical components, however, change their signs slightly below the crest level, indicating a changeover of the dominance of the bursting events. For the TKE budget, the TKE production, diffusion, and pressure energy diffusion rat...

Habitat requirements and ecological niche of two cryptic amphipod species at landscape and local scales

AbstractCryptic species are phylogenetically diverged taxa that are morphologically indistinguishable and may differ in their ecological and behavioral requirements. This may have important implications for ecosystem services and conservation of biodiversity. We investigated whether two ecologically important cryptic species of the freshwater amphipod Gammarus fossarum (types A and B) are associated with different habitats. We collected data on their occurrence at both the landscape scale (large watersheds) and at the local scale (river reach) to compare macro‐ and microscale environmental parameters associated with their presence. Analysis of the landscape scale data showed that occurrence of types A and B differ with respect to watershed and river size and, interestingly, human impact on river ecomorphology. Whereas type B was mainly found in less forested areas with higher human impact, type A showed the opposite occurrence pattern. Analyses of the local scale data suggested that habitats occupied by type A were characterized by larger gravel, larger stones and less macrophytes than habitats occupied by type B. The landscape and local data set showed contradicting patterns with regard to stream size. Overall, the observed differences between the two types of G. fossarum most likely reflect ecological differences between them, but alternative explanations (e.g., historical colonization processes) cannot be completely ruled out. Our study underlines that common cryptic species can differ in their ecology and response to anthropogenic influence. Such differences in habitat requirements among difficult‐to‐identify taxa present a challenge for biodiversity and ecosystem management. Our results emphasize the importance of conservative and precautionary approaches in maintenance of habitat diversity and environmental heterogeneity.

Spawn Timing and Redd Morphology of Anadromous Coastal Cutthroat Trout Oncorhynchus clarkii clarkii in a Tributary of South Puget Sound, Washington

AbstractSpawn timing information for Coastal Cutthroat Trout Oncorhynchus clarkii clarkii is typically limited to counts of adult fish at traps and tagging studies based on few samples. These types of data have suggested a protracted spawning period that occurs between November and March. We sought to determine the spawn timing and describe the redd morphology of anadromous Coastal Cutthroat Trout in a typical coastal stream of southern Puget Sound, Washington. Skookum Creek was surveyed for live and dead Coastal Cutthroat Trout and redds once weekly from early October to early June during six spawning season (2008–2014). In total, 148 live adults and 544 redds were observed. The timing of redd construction was highly variable among years, with 50% of redd detections occurring by as early as February 13 or as late as April 27. Measurements were collected from individual redds to describe redd morphology and the habitat type utilized by spawning Coastal Cutthroat Trout. Redds were typically found in substrate composed of small gravel (1.3–3.8 cm) and large gravel (3.8–7.6 cm) and in water with an average velocity of 0.60 m/s. The pit within redds averaged 0.43 m wide × 0.48 m long. Information from this study may provide new insights that will allow fisheries managers to begin developing a species‐specific approach to monitoring anadromous Coastal Cutthroat Trout.Received July 2, 2015; accepted December 2, 2015 Published online March 31, 2016

Smart rocks teach river lessons

Hydrology Rivers are conveyor belts of erosion, transporting material from continents to the oceans. Measuring how larger gravel and cobbles travel along a riverbed is challenging because of the stochastic nature of grain movement and the dependence on infrequent yet powerful flood events. Olinde

Nesting microhabitat comparison of Central stoneroller and Bluehead chub: potential inference for host-switching by nest associates

Several nest-building North American minnows (Cyprinidae) function as reproductive hosts to nest associates–species that require nests of other species for spawning. Understanding the microhabitat preferences of hosts can yield insight into the reproductive ecology of many species, especially of nest associates that can utilize nests of two or more hosts. We observed nests of Central stoneroller Campostoma anomalum in which several associate species were actively spawning. Bluehead chubs Nocomis leptocephalus began constructing nests two days later in the same stream, at which time associates abandoned stoneroller nests and continued on to spawn on chub nests. This presented a unique opportunity for accomplishing two objectives: (1) quantifying stoneroller nesting microhabitat preference and (2) comparing stoneroller and chub habitat preference to gain insight into the mechanisms that may drive host switching by nest associates. We measured substrate size, current velocity, water depth, and egg depth on seven paired stoneroller and chub nests, and compared these measurements to paired microhabitat measurements at a randomly selected point near each nest. Repeated measures analysis of variance with post hoc Tukey tests revealed that stonerollers exhibited distinct nesting microhabitat preferences from chubs. Gravel on stoneroller nests was considerably smaller than on chub nests and stonerollers nested in shallower depths than chubs. However, both species nested at similar current velocities. If nest associates switch partners based on the physical characteristics of nests, then substrate size is likely the most important factor. The larger gravel sizes on chub nests likely provide better egg aeration than stoneroller nests. Chub nests may also be safer for associate broods because male Bluehead chubs cover eggs with gravel after spawning; stonerollers do not. Future work should take an experimental approach to elucidate these mechanisms.

Computed tomography of scalp embedded gravel: Differentiation between falling and kicking

Abstract In the case of a survived head injury of a 39 year old man, kick versus fall as mechanism had to be discerned. On top of conventionally used medicolegal findings, clinical computed tomography (CT) scans were evaluated. There, dense particles at the back of the head were scattered on and in the skin, around the region also likely to be the center of an impact related skull burst fracture. Experiments then were conducted to discern falling, kicking and scrubbing, based on gravel particle details, using suitable model substrate materials. Particle size and count were larger in falls without scrubbing than in kicks also because soles may not retain heavier or larger gravel particles. Based on chemical composition obtained through EDS (energy-dispersive X-ray spectroscopy), gravel particle mass attenuation coefficient was determined, linearly correlating with effective CT attenuation of scalp particles and bone and skin materials. Gravel particle size showed to be a stronger evidence in the distinction of fall versus kick than skin and brain morphology. Clinical CT can be a valuable asset in reconstructive forensic medicine.

Aspect-dependent soil saturation and insight into debris-flow initiation during extreme rainfall in the Colorado Front Range

Hydrologic processes during extreme rainfall events are poorly characterized because of the rarity of measurements. Improved understanding of hydrologic controls on natural hazards is needed because of the potential for substantial risk during extreme precipitation events. We present field measurements of the degree of soil saturation and estimates of available soil-water storage during the September 2013 Colorado extreme rainfall event at burned (wildfire in 2010) and unburned hillslopes with north- and south-facing slope aspects. Soil saturation was more strongly correlated with slope aspect than with recent fire history; south-facing hillslopes became fully saturated while north-facing hillslopes did not. Our results suggest multiple explanations for why aspect-dependent hydrologic controls favor saturation development on south-facing slopes, causing reductions in effective stress and triggering of slope failures during extreme rainfall. Aspect-dependent hydrologic behavior may result from (1) a larger gravel and stone fraction, and hence lower soil-water storage capacity, on south-facing slopes, and (2) lower weathered-bedrock permeability on south-facing slopes, because of lower tree density and associated deep roots penetrating bedrock as well as less intense weathering, inhibiting soil drainage.

Pilot-scale evaluation of an in situ amendment delivery and mixing device for contaminated sediment remediation applications

In situ sediment treatment technologies can be more economical alternatives than dredging and ex situ treatment; however, their development and application had been hindered due to uncertainties associated with the homogeneity of amendment delivery and mixing and the concern of contaminated sediment resuspension and amendment release into the water column. The purpose of this study was to evaluate the subaqueous amendment delivery and mixing efficiency of a novel pilot scale in situ sediment remediation system addressing these concerns. The in situ sediment treatment system consisted of a hydraulically operated steel casing that provided contained conditions for amendment delivery and mixing to occur and the mixing tool housed by this casing. The mixing tool consisted of a hollow vertical shaft with horizontal mixing blades. The device was capable of delivering amendments to subaqueous sediments during continuous mixing in the downward or upward vertical direction. Activated carbon was used as a tracer to evaluate the efficiency of reagent delivery and mixing. The delivery and mixing system operation was defined by the following parameters: mixing speed, vertical descent or ascent speed, mixing time, total processing time, sediment mixing depth, activated carbon slurry injection volume, pumping flow rate for activated carbon, and pumping pressure for activated carbon. Better amendment yield recoveries were observed at lower added activated carbon volumes, at higher mixing speeds, at lower pump flow rates, in case of thicker mixed sediment zones, and at horizontal locations closer to the center shaft. In general, poor amendment recoveries could be attributed to the limited capacity of the sediment pore space to accommodate the activated carbon slurry. Better recoveries close to the shaft might have occurred due to the fact that the amendment delivery pressure was not controlled and therefore was not constant through each reagent delivery port. The reagent stayed within the enclosure of the device, indicating that contained mixing conditions were achieved. The majority of the suspended sediment settled out fairly quickly from the overlying water column within the enclosure. The in situ remediation system showed potential in terms of successful amendment delivery and mixing into subaqueous sediments. Lower doses of activated carbon were mixed in more efficiently due to the limited availability of pore capacity and issues with powdered activated carbon retention in the sediment. The demonstration took place in sediments with large sand and gravel fractions; sediments containing larger silt and clay fractions are likely to behave differently in terms of sediment resuspension.

Estimation of the shear strength of gravel deposits based on field investigated geological factors

A gravel deposit is a composite material composed of gravel and soil matrix. The largest size of gravel in the study areas generally ranges from 100mm to 300mm. The estimation of the shear strength of gravel deposits often requires large-scale in situ direct shear tests or large-scale triaxial tests in laboratory. Both kinds of the large-scale tests are expensive, and the triaxial tests using remolded specimens with reduced-size gravel may lower estimate the shear strength of gravel deposits. This study first estimates the shear strength of gravel deposits employing their topographic characteristics, which are the envelopes of slope inclinations and slope heights. Each envelope corresponds to a strength parameter of a gravel deposit. Then, field investigation is conducted to obtain geological factors such as the diameter in the grain size distribution curve corresponding to 50% finer (D50), gravel content, and the unconfined compressive strength of matrix. The strength parameter and the field investigated geological factors are correlated through linear regression. The geological factor that most influences the shear strength of the studied gravel deposits is the unconfined compressive strength of matrix. The regression model is tested using field investigated data obtained from other locations, and the derived cohesion and friction angles are compared to the results in literature. The study establishes an economic way to estimate the shear strength of gravel deposits in central Taiwan. However, the idea is applicable to gravel deposits, bimrock, alluvium, or colluvium elsewhere in the world, in which large gravels or cobbles exist and shear strength cannot be estimated by conventional methods.

Reduced-complexity modeling of braided rivers: Assessing model performance by sensitivity analysis, calibration, and validation

[1] This paper addresses an important question of modeling stream dynamics: How may numerical models of braided stream morphodynamics be rigorously and objectively evaluated against a real case study? Using simulations from the Cellular Automaton Evolutionary Slope and River (CAESAR) reduced-complexity model (RCM) of a 33 km reach of a large gravel bed river (the Tagliamento River, Italy), this paper aims to (i) identify a sound strategy for calibration and validation of RCMs, (ii) investigate the effectiveness of multiperformance model assessments, (iii) assess the potential of using CAESAR at mesospatial and mesotemporal scales. The approach used has three main steps: first sensitivity analysis (using a screening method and a variance-based method), then calibration, and finally validation. This approach allowed us to analyze 12 input factors initially and then to focus calibration only on the factors identified as most important. Sensitivity analysis and calibration were performed on a 7.5 km subreach, using a hydrological time series of 20 months, while validation on the whole 33 km study reach over a period of 8 years (2001–2009). CAESAR was able to reproduce the macromorphological changes of the study reach and gave good results as for annual bed load sediment estimates which turned out to be consistent with measurements in other large gravel bed rivers but showed a poorer performance in reproducing the characteristics of the braided channel (e.g., braiding intensity). The approach developed in this study can be effectively applied in other similar RCM contexts, allowing the use of RCMs not only in an explorative manner but also in obtaining quantitative results and scenarios.

조립재료의 입도특성에 따른 동적 변형특성 평가

굵은 자갈 이상의 대입경 입자를 포함하는 조립질 지반재료는 댐, 제방, 철도 등 대형 지반구조물의 성토 및 채움재료로 널리 사용되며, 이러한 구조물의 동적 해석을 위해서는 축조재료의 변형특성에 대한 엄밀한 평가가 필수적이다. 본 연구에서는 대입경 조립재료의 동적 변형특성 평가를 위하여 지름 200mm, 높이 400mm의 공시체에 대한 시험이 가능하도록 개발된 대형 공진주시험기를 활용하여 댐 축조용 사력재의 최대전단탄성계수, 전단탄성계수감소곡선 및 감쇠비를 평가하였으며, 재료의 최대입경과 균등계수와 같은 입도분포특성이 재료의 변형특성에 미치는 영향을 확인하였다. 재료의 입경이 동적 변형특성에 미치는 영향을 평가한 결과, 동일한 균등계수에서 평균입경의 범위에 따른 전단탄성계수감소곡선에 차이가 발생함을 확인하였다. 동일한 최대입경에 대하여 균등계수를 달리하는 경우 균등계수에 따라 최대전단탄성계수의 구속압 영향계수가 증가함을 확인하였다. 결과적으로 조립재료의 입도 특성 중 최대입경은 전단탄성계수감소곡선을, 균등계수는 미소변형영역의 구속압 영향계수에 대한 영향요소임을 확인하였으며, 조립재료의 동적 변형특성을 엄밀히 평가하기 위한 대형 공진주시험기의 효용성을 확인하였다. Coarse granular geomaterials containing large gravels are broadly used for construction of large geotechnical systems such as dams, levees, railways and backfills. It is necessary to evaluate deformation characteristics of these materials for dynamic analysis, e.g. seismic design. This study presents evaluation of dynamic deformation characteristics of coarse materials using large scale resonant column testing apparatus, which uses specimens with 200 mm in diameter and 400 mm in height, and the effects of gradation characteristics on maximum shear modulus, shear modulus reduction curve and damping characteristics were investigated. From experimental study using rock-fill materials for a dam, we could see that the largest or mean particle size affects the shape of shear modulus reduction curve. When the specimens are prepared under the same conditions for maximum particle size, the coefficient of uniformity affects the confining stress exponent of maximum shear modulus. It could be concluded that the maximum particle size is an factor which affects shear modulus reduction curve, and that the coefficient of uniformity is for small strain shear modulus, especially for the sensitivity to confining stress.

Microhabitat use of the diamond darter

AbstractThe only known extant population of the diamond darter (Crystallaria cincotta) exists in the lower 37 km of Elk River, WV, USA. Our understanding of diamond darter habitat use was previously limited, because few individuals have been observed during sampling with conventional gears. We quantified microhabitat use of diamond darters based on measurements of water depth, water velocity and per cent substrate composition. Using spotlights at night‐time, we sampled 16 sites within the lower 133 km of Elk River and observed a total of 82 diamond darters at 10 of 11 sampling sites within the lower 37 km. Glides, located immediately upstream of riffles, were the primary habitats sampled for diamond darters, which included relatively shallow depths (<1 m), moderate‐to‐low water velocities (often < 0.5 m·s−1) and a smooth water surface. Microhabitat use (mean ± SE) of diamond darters was estimated for depth (0.47 ± 0.02 m), average velocity (0.27 ± 0.01 m·s−1) and bottom velocity (0.15 ± 0.01 m·s−1). Substrate used (mean ± SE) by diamond darters was predominantly sand intermixed with lesser amounts of gravel and cobble: % sand (52.1 ± 1.6), % small gravel (12.2 ± 0.78), % large gravel (14.2 ± 0.83), % cobble (19.8 ± 0.96) and % boulder (1.6 ± 0.36). Based on our microhabitat use data, conservation and management efforts for this species should consider preserving glide habitats within Elk River. Spotlighting, a successful sampling method for diamond darters, should be considered for study designs of population estimation and long‐term monitoring.

An assessment of the degree to which Landsat TM data can support the assessment of fluvial dynamics, as revealed by changes in vegetation extent and channel position, along a large river

Recent research has demonstrated the capacity of remotely sensed data to enhance our understanding of interactions between fluvial processes and riparian vegetation. Multispectral Landsat TM satellite data covering the last 30years are now freely available and have the potential to support investigations at much broader spatial and temporal scales than previously possible. This paper assesses the degree to which this data set can support the assessment of fluvial dynamics along a large gravel bed river, the Fiume Tagliamento, NE Italy. Landsat TM scenes are used to determine spatio-temporal trends in vegetation cover and channel position at six sites of contrasting environmental conditions along the river. These trends are interpreted in combination with a number of additional hydrogeomorphological data sets before comparison with known biogeomorphological characteristics of the study sites as revealed by previous field research and analyses of higher resolution remotely sensed data sets. The research highlights a number of limitations with Landsat TM data that arise as a result of its relatively low spatial resolution including geomorphic feature definition and active tract delineation. Nevertheless, the analysis demonstrates that Landsat TM data can reveal a wealth of information that could support further biogeomorphological investigations in other large rivers.

Effects of Meso-Structure Characters on Fracture Properties and Fracture Mechanism in Concrete

To understand relationship between the meso-structure of non-homogeneous materials and the fracture properties, two groups of concrete specimens are designed and tested. For the two groups with the same water-cement ratio and coarse aggregate volume ratio, small and large grain size gravels are used respectively. Since both groups of materials are with the same mass ratio of coarse aggregates, the heterogeneity of the gravels distribution in concrete with larger grain size is higher than the other. The results show that the group with smaller aggregate grain size gains higher material fracture strength and fracture energy than another group. Then the concrete with more homogeneous meso-structure will reach higher fracture properties

교과서에서 사용하는 퇴적물의 입도에 대한 한국어 용어의 검토

The Korean terms of sediment grain size demonstrated in the 30 textbooks of elementary, middle, and high schools and university levels are compared and reviewed, and the problems of its use and alternative terms are proposed. The Korean terms of sediment grain size shown in the most textbooks are the translated terms of the Udden-Wentworth grade scale, and the different terms have been used in these textbooks. In the case of gravels, granule, cobble, and boulder have commonly been translated as wangmorae (king sand), janjagal (fine gravel), wangjagal (king gravel), and pyoryeog (drift gravel) or georyeog (large gravel), respectively. However, it is regarded to be reasonable that they are termed as janjagal, jungjagal (medium gravel), keunjagal (large gravel), and wangjagal, respectively. Adjectives such as 'maeu goun' (very fine), 'goun' (fine), 'junggan' (medium), 'gulgeun' (coarse), and 'maeu gulgeun' (very coarse), attached with each sediment name seem to be suitable to terms for sediments smaller than gravels. Silt has been commonly termed as misa (fine sand) in many textbooks, but it may be appropriate that silt is expressed as silt. Finally, mud, which is a mixture of silt and clay, should be named ito (mud) as shown in several textbooks including Dictionary of Korean Earth Science, though mud has been frequently termed as jinheug (slush or watery soil) in the most of textbooks for elementary and middle school students, and some high school and university textbooks.