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Design tools
Published in G.J.C.M. Hoffmans, H.J. Verheij, Scour Manual, 2021
G.J.C.M. Hoffmans, H.J. Verheij
Overall degradation at, for example, a bridge site lowers the bed level and may thereby increase the risk of failure of the foundations. Aggradation, on the contrary, will cause higher water levels and may reduce the risk from scour. Degradation processes already in progress have to be considered, as well as the possibility of inducing degradation processes in the future (e.g. seasonal degradation). Overall degradation can affect a long reach of the river, extending over tens to hundreds of kilometres and over periods of decades to centuries (de Vries, 1975). Examples are the Bovenrijn and Waal branches of the river Rhine in the Netherlands which experience general bed degradation due to enhanced sediment transport capacity and reduced sediment supply from upstream.
Rock mass formation
Published in Ivan Gratchev, Rock Mechanics Through Project-Based Learning, 2019
Bedding planes divide rocks into beds or strata; they represent interruption in the sedimentary process or repeated sedimentation cycles. Bedding planes can exist in one rock type (e.g., sandstone) or be an alternation of two or three types of rock (e.g., sandstone and argillite, Figure 3.8). When two rocks form bedding planes, such a geological structure is also referred to as flysch. It is noted that over time, bedding planes can become potential weathered zones and contain pockets of ground water.
Stratigraphy
Published in Dexter Perkins, Kevin R. Henke, Adam C. Simon, Lance D. Yarbrough, Earth Materials, 2019
Dexter Perkins, Kevin R. Henke, Adam C. Simon, Lance D. Yarbrough
The stratigraphy and formations of the Grand Staircase and Grand Canyon are typical of continental regions where relatively flat-lying sedimentary rocks are found. If a sedimentary layer or formation extends over a large area, outcrops made of identical kinds of rocks can be correlated (matched with rock units of the same age but in different places), even if a valley or other erosional feature separates them. The areal extent, thickness, and compositions of different kinds of beds, and their relationships with beds above and below them, allow geologists to reconstruct geological histories. So, studying stratigraphy is important for the wealth of information it provides about Earth’s evolution, the evolution of life, and the history of civilization. It is also important because it can guide coal, oil, gas, and mineral exploration.
Heavy metal distribution in various environmental matrices and their risk assessment in Ganga River Basin, India
Published in Human and Ecological Risk Assessment: An International Journal, 2023
Anshula Dhiman, AL Ramanthan, Mark Macklin, Shailesh Yadav, Stuti Kushwaha, Amogh Mudbhatkal, Venkatramanan Senapathi
The conceptual model delineates the processes controlling the heavy metal dissolution and deposition in river water, bed sediment, and SPM. The extended suspension of metals in suspended particles in the water column and deposition in bed sediment were controlled by the natural process (weathering and erosion), anthropogenic contamination, biogeochemical enrichment, and hydrological regime of the river. For maintaining the equilibrium with the water column, SPM is undergoing rapid alterations (Zhang Q et al. 2020). During the process of river evolution, heavy metals introduced into the river water, first come in contact with SPM as the initial constituent to interact and adsorb them onto particle surfaces. The SPM settles and contributes to the bed sediment, thereby decreasing its interaction with the water column above (Figure 7). Bed sediment was also accumulating heavy metals wherever there is high silt, clay, and OC percentage. Thus, the increased load of the suspended particle during the monsoon has enhanced the river’s capability of removing pollution load from the water via scavenging heavy metals primarily by SPM because of the larger contact area and prolonged suspension in the water column than bed sediment and transporting heavy metal downstream (Feng et al. 2017). In addition, the higher percentage of clay-sized particles and organic carbon in SPM led to greater metal enrichment in SPM (Singh 2007). The conceptual model revealed crucial role of SPM and bed sediment in controlling metal pollution by various geochemical processes like adsorption and transport in the river system. Figure 7.
Implications of geotechnical properties on the sediment resuspension and heavy metal partitioning in Ashtamudi estuary, India
Published in Marine Georesources & Geotechnology, 2021
Febina A. Manaf, Priya K. L., Reji Srinivas, Sreeraj M. K.
Table 3 represents the vane shear strength and the consolidation coefficient of sediments at each location. It was observed that the bed sediments at locations 2 and 3 exhibited lower consolidation coefficient and shear strength, which indicates the higher chances of erosion at these locations. A lower consolidation coefficient indicates lower bond strength between the particles, which further results in lower shear strength. Irrespective of the clay content present at these locations, lower consolidation coefficient and shear strength are exhibited due to the presence of considerable amounts of sand. When a fluid shear in excess of the shear strength of the bed sediment acts on them, the sediment experiences erosion, which can lead to mass erosion or particle-particle erosion.
Developing community marine data service for Blue Growth sectors
Published in Journal of Operational Oceanography, 2019
Another large cost factor is the setting of the foundations during the construction phase of a bottom-fixed wind turbine and the installation of the piles. The cost is related to bathymetry, seabed slope, geology and hydro- and sediment dynamic near the sea bed. The average and extreme met-ocean conditions at the site, as well as the typical length and number of periods in which these conditions occur, are important for estimating the construction and maintenance cost, which can be quantified for certain vessel types and specific operations. It is necessary to provide additional information about typical weather windows with critical wind speed and wave height for certain operations, dependent on the type of operation and vessel at hand. Calm conditions are also required for a minimum period, e.g. 6 h for on-site operations and about 24 h for transport operations. More complicated operations would require additional information about fog, icing and eventual lightning, which have not been considered so far.