Deep excavation caused by water is called undermining. One of the types of water erosion can be due to the impact of waves against a cliff, to the eddies of water, especially where the current encounters an obstacle, and to friction with the banks of the currents that have been diverted by the sinuous beds. In the latter case it is faster in the first phase of the avenues "Avenue (hydrology)"). The undercutting causes the retreat of the waterfalls and cliffs which, being deprived of support at their base, progressively collapse. It also plays an essential role in the formation and migration of meanders.
Guys
Contenido
Se pueden distinguir dos tipos de socavación:.
• - La socavación general; y,.
• - La socavación localizada.
General Undermining
General erosion is a long-term phenomenon, which we could call natural, it occurs in the upper part of the hydrographic basins, where the slope "Slope (geography)") of the talweg "Vaguada (geomorphology)") is high. As a consequence, the speed of the water and the drag capacity of the current is high. As the flow drags more material, the flow quickly reaches its potential drag capacity, which is a function of speed. At that point it no longer produces scour, the section, margins and bottom are stable. As you advance along the course of the river or stream, the slope decreases, consequently the speed decreases, and the current deposits the material it was transporting.
Localized undermining
The most typical cases of localized scour are:
• - At the foot of a slope "Slope (geology)"), which could cause its collapse, if measures are not taken;
• - Around the pillars, or under the foundation of the head of a bridge, which could cause the bridge to fall.
• - Immediately downstream of a reservoir. In effect, the reservoir retains almost all of the solid transport of the river, thus, the water that is discharged downstream of the dam is almost completely free of sediment, therefore having a considerable scour capacity.
Scour collapse
Introduction
Deep excavation caused by water is called undermining. One of the types of water erosion can be due to the impact of waves against a cliff, to the eddies of water, especially where the current encounters an obstacle, and to friction with the banks of the currents that have been diverted by the sinuous beds. In the latter case it is faster in the first phase of the avenues "Avenue (hydrology)"). The undercutting causes the retreat of the waterfalls and cliffs which, being deprived of support at their base, progressively collapse. It also plays an essential role in the formation and migration of meanders.
Guys
Contenido
Se pueden distinguir dos tipos de socavación:.
• - La socavación general; y,.
• - La socavación localizada.
General Undermining
General erosion is a long-term phenomenon, which we could call natural, it occurs in the upper part of the hydrographic basins, where the slope "Slope (geography)") of the talweg "Vaguada (geomorphology)") is high. As a consequence, the speed of the water and the drag capacity of the current is high. As the flow drags more material, the flow quickly reaches its potential drag capacity, which is a function of speed. At that point it no longer produces scour, the section, margins and bottom are stable. As you advance along the course of the river or stream, the slope decreases, consequently the speed decreases, and the current deposits the material it was transporting.
Localized undermining
The most typical cases of localized scour are:
• - At the foot of a slope "Slope (geology)"), which could cause its collapse, if measures are not taken;
• - Around the pillars, or under the foundation of the head of a bridge, which could cause the bridge to fall.
This is a type of scour that consists of the excavation of material found around the pillars of a bridge, which can lead (if applicable) to the collapse of the structure. Among the best-known formulas for predicting scour depth around pillars founded on sandy beds are those of HEC-18 (FHWA Hydraulic Engineering Circular and FDOT (Florida Department of Transportation), through data analysis it has been observed that each of these formulas have a certain range of application; that is, ranges where the value of the predicted scour is closer to the calculated one.[1].
In a statistic carried out in 1976, on the causes of failure or breakage of 143 bridges around the world, it turned out:
• - 1 failure due to corrosion.
• - 4 to the fatigue of the materials.
• - 4 to the wind,.
• - 5 to an inadequate structural design.
• - 11 earthquakes.
• - 12 to an inadequate construction procedure.
• - 14 failures were due to overloading or impact of vessels.
• - 22 for defective materials and finally.
• - 70 failures were caused by floods (of which 66 were due to scour, 46% of the total).
This shows that hydraulic aspects are fundamental in bridges; A good knowledge of these aspects will make the bridge safer and cheaper.[2].
• - Immediately downstream of a reservoir. In effect, the reservoir retains almost all of the solid transport of the river, thus, the water that is discharged downstream of the dam is almost completely free of sediment, therefore having a considerable scour capacity.
This is a type of scour that consists of the excavation of material found around the pillars of a bridge, which can lead (if applicable) to the collapse of the structure. Among the best-known formulas for predicting scour depth around pillars founded on sandy beds are those of HEC-18 (FHWA Hydraulic Engineering Circular and FDOT (Florida Department of Transportation), through data analysis it has been observed that each of these formulas have a certain range of application; that is, ranges where the value of the predicted scour is closer to the calculated one.[1].
In a statistic carried out in 1976, on the causes of failure or breakage of 143 bridges around the world, it turned out:
• - 1 failure due to corrosion.
• - 4 to the fatigue of the materials.
• - 4 to the wind,.
• - 5 to an inadequate structural design.
• - 11 earthquakes.
• - 12 to an inadequate construction procedure.
• - 14 failures were due to overloading or impact of vessels.
• - 22 for defective materials and finally.
• - 70 failures were caused by floods (of which 66 were due to scour, 46% of the total).
This shows that hydraulic aspects are fundamental in bridges; A good knowledge of these aspects will make the bridge safer and cheaper.[2].