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Keynote Address
Published in C.V.J. Varma, B.S.K. Naidu, A.R.G. Rao, Silting Problems in Hydro Power Plants, 2020
Another characteristics of Indian hydro power scenario is that out of 84044 MW economically exploitable hydro power potential at 60% load factor, 65,623 MW lies in rivers basins of Indus, Ganges, Brahmaputra, which originate from young Himalayas. Himalayas are world's youngest mountains just 15 millions years old. These rivers carry huge silt, which is sometimes of the order of 15,000 ppm in rainy season. For some rivers even it could be higher than 30,000 ppm. The direct impact of the silt is hindrance in operation of water resources projects as it decreases the total water carrying capacity of reservoirs in the course of time. The silt not only affects the reservoir capacity but also causes erosion of civil structures and damages electro-mechanical equipment and accordingly silt problem is to be managed on all these fronts in a cost-effective manner.
Environmental Impacts from Groundwater Control
Published in Pat M. Cashman, Martin Preene, Groundwater Lowering in Construction, 2020
Suspended solids, in the form of clay, silt and occasionally sand-sized particles, are a common problem resulting from dewatering discharges. Silt discharges are a highly visible aesthetic problem (Figure 21.16), but silt also harms aquatic plant, fish and insect life and can build up in watercourses, blocking flow.
Erosion
Published in Karlheinz Spitz, John Trudinger, Mining and the Environment, 2019
Karlheinz Spitz, John Trudinger
A silt fence or sediment filter is relatively simple to install and is a down-gradient barrier intended to intercept sheet flow runoff and settle out sediment upslope while allowing runoff to filter through. A silt fence or sediment filter can be used to control exit runoff and sediment load from small disturbed areas. For larger areas a series of filters may need to be installed at appropriate intervals (Figure 25.11). A silt fence works particularly well in conjunction with an existing vegetative buffer strip running across a slope – the vegetation cover helps dissipate the energy of runoff, while silt fences collect sediment. However, as mentioned in an earlier section, a silt fence or sediment filter is less effective if well-defined channels coming from the disturbed land exist. Concentrated water flow requires other measures.
Mechanical and microstructural properties of silt roadbed filling improved with cement, red mud and desulfurization gypsum
Published in European Journal of Environmental and Civil Engineering, 2023
Sai Zhang, Jianwen Ding, Zhenyuan Lai, Qinying Guo, Xing Wan
Metro station is an important part of urban rail transportation, whose construction is often carried out through large-scale pit excavations and generates large numbers of excavated soils. These excavated soils are often abandoned or stockpiled, which not only occupies significant land resources, but also increases construction costs due to the transportation of abandoned soils from construction site to stockyard. Notably, the abandoned soils can used in roadbed construction where considerable filling materials are required. The soils with good engineering properties can be used as filling materials directly. On the contrary, the soils with poor engineering properties must be pre-treated before engineering application (Zhao et al., 2017; Chen et al., 2019). For example, silt has a low strength and is difficult to be compacted, which may cause uneven settlement of the roadbed and further lead to road cracking, water damage or other disasters (Yuan et al., 2016; Iadovina & Mashchenko, 2017). Hence, the silt excavated from the metro station construction site needs to be improved before used as roadbed filling.
ArcGIS mapping, characterisations and modelling the physical and mechanical properties of the Sulaimani City soils, Kurdistan Region, Iraq
Published in Geomechanics and Geoengineering, 2022
Chro Ahmed, Ahmed Mohammed, Alia Saboonchi
Silt and clay content if present in large percentage, is problematic for the foundation of buildings. Therefore, it is necessary to evaluate its presence. The range of percentage of silt and clay at 1.5 m depth is 27% to 97%, and the minimum silt and clay content go on decreasing as going deeper into the soil reaching at 5% at 6 m depth. The average silt and clay content vary from 97% at 1.5 m to 27% at 6 m depth. The standard deviation of the silt and clay content at 1.5 m depth is 18.6 but at 6.0 m depth, its value is 22. The coefficient of variation ranges between 0.28 and 0.82, which signifies that variation goes on increasing with depth (Figure 6).
Assessing long-term evolution of the fine sediment budget in the Iffezheim reservoir: temporal upscaling of numerical simulations
Published in International Journal of River Basin Management, 2022
Qing Zhang, Gudrun Hillebrand, Thomas Hoffmann, Reinhard Hinkelmann
The grain size distribution of suspended load is taken from measurements at Rhine-km 330.0 in June 2012. The material in suspension largely consists of silt and clay. While grain size distribution may be expected to be dependent on discharge, the observed variations in the Rhine were of minor importance and showed no clear correlation to discharge (Astor et al., 2014). The d50 typically is in the range of 0.01–0.03 mm (Astor et al., 2014; Frings et al., 2019). Hysteresis effects of grain size distribution during floods have also been observed at a gauging station at the Rhine further downstream of the study area, with larger grain sizes in the early stages of a flood events and smaller grain sizes during decreasing discharges (unpublished data). However, observed changes in d50 were within the range of the chosen size classes of the model. Thus, grain size distribution of the model input was assumed to be constant. Along the riverbed, the grain size distribution has a non-uniform spatial pattern. The weir channel is the main area of deposition in the reservoir. Deposited sediments largely consist of silt with varying portions of clay and sand. Deposition is concentrated on the left and middle section of the weir channel. Accordingly, cohesive sediments are found in this area. On the right hand of the weir channel and in the upstream part of the reservoir, coarser sediments are found. This is the location and grain size composition of the original river bed before the dam was built. Initial conditions for the grain size distribution in the model are derived from measured bed grain size distributions within the weir channel and in the upstream region of the reservoir. For discretization of sediments, the continuous initial bed sediment sieve curve was decomposed into 9 size fractions. Fractionation of suspended load and material on the riverbed are used in the numerical simulation (Figure 4).