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Aggregates
Published in M. Rashad Islam, Civil Engineering Materials, 2020
Boulders and cobbles are not included in the category of aggregates. These are crushed down into other smaller sizes. Gravel is known as the particles with sizes greater than 4.75 mm (#4 sieve) and smaller than cobbles. It is further divided into coarse gravel and fine gravel. Sand is greater than 0.075 mm (# 200 sieve) but smaller than gravel. It is further divided into coarse sand, medium sand, and fine sand. Anything finer than sand is called the fine aggregates, or simply fines. They are further classified into silt and clay based on their cohesion properties. Silt is cohesionless (does not stick together) and clay has cohesion, i.e., the property in which a material becomes sticky upon adding water.
Shock test on rounded rock fragments in Suruga Bay sediments and its implications on past mega-earthquakes
Published in Ömer Aydan, Takashi Ito, Takafumi Seiki, Katsumi Kamemura, Naoki Iwata, 2019 Rock Dynamics Summit, 2019
The size of rock fragments having different sizes are called gravel or pebble (2-64 mm), cobble (64-256mm) or boulders (greater than 264 mm). Therefore, the testing device is limited to gravel/pebble and cobbles with a size less than 100 mm. The samples were collected at Miho-shore along Suruga Bay in which Seno-umi area exist and Kusanagi hill, which is a part of uplifted conglomeratic sea-bed deposits. The first author sampled some pebbles from Seno-umi area in Suruga Bay, Shizuoka by Bousei-maru investigation ship of Tokai University. The pebbles/cobbles in Miho and Kusanagi area are made of sandstone (Figure 3).
Coastal transport processes
Published in Dominic Reeve, Andrew Chadwick, Christopher Fleming, Coastal Engineering, 2018
Dominic Reeve, Andrew Chadwick, Christopher Fleming
As previously mentioned in Chapter 1, most of our beaches today are composed of the remnants of sediments washed down the rivers in the last Ice Age, predominantly sands and gravels. Traditionally the sand and gravel sizes have been classified according to the Wentworth scale. This defines sand as being very fine (0.0625 mm to 0.037 mm), fine (0.037 mm to 0.25 mm), medium (0.25 mm to 0.5 mm), coarse (0.5 mm to 1 mm) and very coarse (1 mm to 2 mm). Material sizes larger than this are classified as gravel, subdivided into granular (2 mm to 4 mm), pebble (4 mm to 64 mm), cobble (64 mm to 256 mm) and boulder (>256 mm). Rounded gravel, typical of a significant number of UK beaches, is referred to as shingle.
Lithofacies characteristics and sedimentary model of a gravelly braided river-dominated fan: a case study of modern Poplar River alluvial fan (northwest Junggar Basin, China)
Published in Australian Journal of Earth Sciences, 2021
D.-W. Liu, Y.-L. Ji, C.-L. Gao, J. Zhong, Y. Qi
One hundred and eight outcrop sections in the Poplar River alluvial fan were described in detail (Figure 1), and 385 outcrop samples were tested in grainsize experiments (silt, sand and gravel) to help distinguishing lithofacies types and depositional environments and detailed flow conditions with corresponding sedimentary textures. Gravel can be further divided into boulders (>256 mm), cobbles (64–256 mm), pebbles (4–64 mm) and granules (2–4 mm) based on diameters. Fifteen longitudinal sections and 15 transverse sections (including nine trial-trenches) were carefully measured from the proximal part to the distal part of the fan. Two-dimensional panels depicting ∼8 km of outcrop demonstrates the pseudo-three-dimensional arrangement of architectural elements, which constitute eight lithofacies associations, enabled the identification of the common geometric relationships between each facies body. Two-dimensional panels depict: (i) detailed lateral and vertical facies relationships within individual fluvial channel and sheet-flood complexes; (ii) differences in the lateral and vertical facies relationships between braided-fluvial channel complexes and braided-trench channel complexes; (iii) the geometry of various architectural elements, including fluvial and debris-flow architecture complexes; (iv) classification of the sedimentary environments and summarised interactions and relationships between each lithofacies association; (v) proximal to distal changes in the style of sedimentation; and (vi) three-dimensional changes in the style of sedimentation from proximal to distal parts.