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Jet Erosion Test
The jet erosion test (JET), or jet index test, is a method used in geotechnical engineering to quantify the resistance of a soil to erosion. The test can be applied in-situ after preparing a field site, or it can be applied in a laboratory on either an intact or a remolded soil sample. A quantitative measure of erodibility allows for the prediction of erosion, assisting with the design of structures such as vegetated channels, road embankments, dams, levees, and spillways.ASTM D5852-00. Procedure The test consists of mounting a jet tube inside of an enclosed cylinder and releasing a turbulent downpour of water onto a soil specimen at a constant hydraulic head. If the shear stress applied by the jet stream exceeds the critical shear stress for erosion of the soil, the jet will erode soil particles, causing a scour Scour may refer to: Hydrodynamic processes * Hydrodynamic scour, the removal of sediment such as sand and silt from around an object by water flow ** Bridge s ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Geotechnical Engineering
Geotechnical engineering, also known as geotechnics, is the branch of civil engineering concerned with the engineering behavior of earth materials. It uses the principles of soil mechanics and rock mechanics to solve its engineering problems. It also relies on knowledge of geology, hydrology, geophysics, and other related sciences. Geotechnical engineering has applications in military engineering, mining engineering, petroleum engineering, coastal engineering, and offshore construction. The fields of geotechnical engineering and engineering geology have overlapping knowledge areas. However, while geotechnical engineering is a specialty of civil engineering, engineering geology is a specialty of geology. History Humans have historically used soil as a material for flood control, irrigation purposes, burial sites, building foundations, and construction materials for buildings. Dykes, dams, and canals dating back to at least 2000 BCE—found in parts of ancient Egypt, ancient Mes ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hydraulic Head
Hydraulic head or piezometric head is a measurement related to liquid pressure (normalized by specific weight) and the liquid elevation above a vertical datum., 410 pages. See pp. 43–44., 650 pages. See p. 22, eq.3.2a. It is usually measured as an equivalent liquid surface elevation, expressed in units of length, at the entrance (or bottom) of a piezometer. In an aquifer, it can be calculated from the depth to water in a piezometric well (a specialized water well), and given information of the piezometer's elevation and screen depth. Hydraulic head can similarly be measured in a column of water using a standpipe piezometer by measuring the height of the water surface in the tube relative to a common datum. The hydraulic head can be used to determine a ''hydraulic gradient'' between two or more points. Definition In fluid dynamics, the ''head'' at some point in an incompressible (constant density) flow is equal to the height of a static column of fluid whose pressure at ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Soil Erosion
Soil erosion is the denudation or wearing away of the Topsoil, upper layer of soil. It is a form of soil degradation. This natural process is caused by the dynamic activity of erosive agents, that is, water, ice (glaciers), snow, Atmosphere of Earth, air (wind), plants, and animals (including humans). In accordance with these agents, erosion is sometimes divided into water erosion, glacial erosion, snow erosion, Aeolian erosion, wind (aeolian) erosion, Zoogenic erosion, zoogenic erosion and anthropogenic erosion such as tillage erosion. Soil erosion may be a slow process that continues relatively unnoticed, or it may occur at an alarming rate causing a serious loss of topsoil. The loss of soil from Agricultural land, farmland may be reflected in reduced crop production potential, lower surface water quality and damaged drainage networks. Soil erosion could also cause sinkholes. Human activities have increased by 10–50 times the rate at which erosion is occurring world-wide. Exc ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hole Erosion Test
The hole erosion test (HET) is a method used in geotechnical engineering to quantify the resistance of a soil to erosion, and is specifically relevant to the topic of internal erosion in embankment dams. The test can be performed in a laboratory on a remolded soil sample, and provides estimates of both the critical shear stress for erosion of the soil sample as well as a numerical measure of soil erodibility. In the design and engineering of embankment dams, the critical shear stress provided by this test indicates the maximum shear stress that a fluid (such as water) can apply to a soil before a concentrated leak forms and erosion begins. The numerical measure of soil erodibility can be used to predict how quickly this erosion will progress, and it can be found as an input in various computer simulations for dam failure. Procedure The standard hole erosion test consists of first compacting the soil sample in a standard mold. Then, a small hole (typically 6mm) is drilled leng ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Erodibility
Erodability (or erodibility) is the inherent yielding or nonresistance of soils and rocks to erosion. A high erodibility implies that the same amount of work exerted by the erosion processes leads to a larger removal of material. Because the mechanics behind erosion depend upon the competence and coherence of the material, erodibility is treated in different ways depending on the type of surface that eroded. Soils Soil erodibility is a lumped parameter that represents an integrated annual value of the soil profile reaction to the process of soil detachment and transport by raindrops and surface flow. The most commonly used model for predicting soil loss from water erosion is the '' Universal Soil Loss Equation (USLE)'' (also known as the K-factor technique), which estimates the average annual soil loss A as: :A = R K L S C P where ''R'' is thrainfall erosivity factor ''K'' is the soil erodibility, ''L'' and ''S'' are topographic factors representing length and slope, and ''C'' and ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hydrodynamic Scour
lang=en, upright=1.3, Mechanism of formation, alt=sketch Hydrodynamic scour is the removal of sediment such as silt, sand and gravel from around the base of obstructions to the flow in the sea, rivers and canals. Scour, caused by fast flowing water, can carve out scour holes, compromising the integrity of a structure. It is an interaction between the hydrodynamics and the geotechnical properties of the substrate. It is a notable cause of bridge failure and a problem with most marine structures supported by the seabed in areas of significant tidal and ocean current. It can also affect biological ecosystems and heritage assets. Mechanism Any obstruction within flowing water will produce changes in velocity within the water column. The flow changes that occur in the vicinity of the substrate may cause differential movement in the bed materials near the obstruction. The magnitude of these changes varies with stream velocity, feature shape and substrate character. Generally the str ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sediment Transport
Sediment transport is the movement of solid particles (sediment), typically due to a combination of gravity acting on the sediment, and the movement of the fluid in which the sediment is entrained. Sediment transport occurs in natural systems where the particles are clastic rocks (sand, gravel, boulders, etc.), mud, or clay; the fluid is air, water, or ice; and the force of gravity acts to move the particles along the sloping surface on which they are resting. Sediment transport due to fluid motion occurs in rivers, oceans, lakes, seas, and other bodies of water due to current (fluid), currents and tides. Transport is also caused by glaciers as they flow, and on terrestrial surfaces under the influence of wind. Sediment transport due only to gravity can occur on sloping surfaces in general, including hillslopes, escarpment, scarps, cliffs, and the continental shelf—continental slope boundary. Sediment transport is important in the fields of sedimentary geology, geomorphology, c ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Shear Stress
Shear stress (often denoted by , Greek alphabet, Greek: tau) is the component of stress (physics), stress coplanar with a material cross section. It arises from the shear force, the component of force vector parallel to the material cross section. ''Normal stress'', on the other hand, arises from the force vector component perpendicular to the material cross section on which it acts. General shear stress The formula to calculate average shear stress or force per unit area is: \tau = ,where is the force applied and is the cross-sectional area. The area involved corresponds to the material face (geometry), face parallel to the applied force vector, i.e., with surface normal vector perpendicular to the force. Other forms Wall shear stress Wall shear stress expresses the retarding force (per unit area) from a wall in the layers of a fluid flowing next to the wall. It is defined as:\tau_w := \mu\left.\frac\_,where is the dynamic viscosity, is the flow velocity, and is the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Turbulence
In fluid dynamics, turbulence or turbulent flow is fluid motion characterized by chaotic changes in pressure and flow velocity. It is in contrast to laminar flow, which occurs when a fluid flows in parallel layers with no disruption between those layers. Turbulence is commonly observed in everyday phenomena such as surf, fast flowing rivers, billowing storm clouds, or smoke from a chimney, and most fluid flows occurring in nature or created in engineering applications are turbulent. Turbulence is caused by excessive kinetic energy in parts of a fluid flow, which overcomes the damping effect of the fluid's viscosity. For this reason, turbulence is commonly realized in low viscosity fluids. In general terms, in turbulent flow, unsteady vortices appear of many sizes which interact with each other, consequently drag due to friction effects increases. The onset of turbulence can be predicted by the dimensionless Reynolds number, the ratio of kinetic energy to viscous damping ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Erosion
Erosion is the action of surface processes (such as Surface runoff, water flow or wind) that removes soil, Rock (geology), rock, or dissolved material from one location on the Earth's crust#Crust, Earth's crust and then sediment transport, transports it to another location where it is deposit (geology), deposited. Erosion is distinct from weathering which involves no movement. Removal of rock or soil as clastic sediment is referred to as ''physical'' or ''mechanical'' erosion; this contrasts with ''chemical'' erosion, where soil or rock material is removed from an area by Solvation, dissolution. Eroded sediment or solutes may be transported just a few millimetres, or for thousands of kilometres. Agents of erosion include rainfall; bedrock wear in rivers; coastal erosion by the sea and Wind wave, waves; glacier, glacial Plucking (glaciation), plucking, Abrasion (geology), abrasion, and scour; areal flooding; Aeolian processes, wind abrasion; groundwater processes; and Mass wastin ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Jet (fluid)
A jet is a stream of fluid that is projected into a surrounding medium, usually from some kind of a nozzle, aperture or orifice. Jets can travel long distances without dissipating. Jet fluid has higher speed compared to the surrounding fluid medium. In the case that the surrounding medium is assumed to be made up of the same fluid as the jet, and this fluid has viscosity, some of the surrounding fluid is carried along with the jet in a process called entrainment. Some animals, notably cephalopods, move by jet propulsion, as do rocket engines and jet engines. Applications Liquid jets are used in many different areas. In everyday life, you can find them for instance coming from the water tap, the showerhead, and from spray cans. In agriculture, they play a role in irrigation and in the application of crop protection products. In the field of medicine, you can find liquid jets for example in injection procedures or inhalers. Industry uses liquid jets for waterjet cutt ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Spillway
A spillway is a structure used to provide the controlled release of water downstream from a dam or levee, typically into the riverbed of the dammed river itself. In the United Kingdom, they may be known as overflow channels. Spillways ensure that water does not damage parts of the structure not designed to convey water. Spillways can include floodgates and fuse plugs to regulate water flow and reservoir level. Such features enable a spillway to regulate downstream flow—by releasing water in a controlled manner before the reservoir is full, operators can prevent an unacceptably large release later. Other uses of the term "spillway" include bypasses of dams and outlets of channels used during high water, and outlet channels carved through natural dams such as moraines. Water normally flows over a spillway only during flood periods, when the reservoir has reached its capacity and water continues entering faster than it can be released. In contrast, an intake tower is a structure ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
