Fracture toughnessIn materials science, fracture toughness is the critical stress intensity factor of a sharp crack where propagation of the crack suddenly becomes rapid and unlimited. A component's thickness affects the constraint conditions at the tip of a crack with thin components having plane stress conditions and thick components having plane strain conditions. Plane strain conditions give the lowest fracture toughness value which is a material property.
Fracture mechanicsFracture mechanics is the field of mechanics concerned with the study of the propagation of cracks in materials. It uses methods of analytical solid mechanics to calculate the driving force on a crack and those of experimental solid mechanics to characterize the material's resistance to fracture. Theoretically, the stress ahead of a sharp crack tip becomes infinite and cannot be used to describe the state around a crack. Fracture mechanics is used to characterise the loads on a crack, typically using a single parameter to describe the complete loading state at the crack tip.
FractureFracture is the separation of an object or material into two or more pieces under the action of stress. The fracture of a solid usually occurs due to the development of certain displacement discontinuity surfaces within the solid. If a displacement develops perpendicular to the surface, it is called a normal tensile crack or simply a crack; if a displacement develops tangentially, it is called a shear crack, slip band or dislocation. Brittle fractures occur without any apparent deformation before fracture.
ToughnessIn materials science and metallurgy, toughness is the ability of a material to absorb energy and plastically deform without fracturing. Toughness is the strength with which the material opposes rupture. One definition of material toughness is the amount of energy per unit volume that a material can absorb before rupturing. This measure of toughness is different from that used for fracture toughness, which describes the capacity of materials to resist fracture. Toughness requires a balance of strength and ductility.
Environmental impact of frackingThe environmental impact of fracking is related to land use and water consumption, air emissions, including methane emissions, brine and fracturing fluid leakage, water contamination, noise pollution, and health. Water and air pollution are the biggest risks to human health from fracking. Research has determined that fracking negatively affects human health and drives climate change. Fracking fluids include proppants and other substances, which include chemicals known to be toxic, as well as unknown chemicals that may be toxic.
Fracture (geology)A fracture is any separation in a geologic formation, such as a joint or a fault that divides the rock into two or more pieces. A fracture will sometimes form a deep fissure or crevice in the rock. Fractures are commonly caused by stress exceeding the rock strength, causing the rock to lose cohesion along its weakest plane. Fractures can provide permeability for fluid movement, such as water or hydrocarbons. Highly fractured rocks can make good aquifers or hydrocarbon reservoirs, since they may possess both significant permeability and fracture porosity.
FrackingFracking (also known as hydraulic fracturing, fracing, hydrofracturing, or hydrofracking) is a well stimulation technique involving the fracturing of bedrock formations by a pressurized liquid. The process involves the high-pressure injection of "fracking fluid" (primarily water, containing sand or other proppants suspended with the aid of thickening agents) into a wellbore to create cracks in the deep-rock formations through which natural gas, petroleum, and brine will flow more freely.
Cerebrospinal fluid leakA cerebrospinal fluid leak (CSF leak or CSFL) is a medical condition where the cerebrospinal fluid (CSF) surrounding the brain or spinal cord leaks out of one or more holes or tears in the dura mater. A cerebrospinal fluid leak can be either cranial or spinal, and these are two different disorders. A spinal CSF leak can be caused by one or more meningeal diverticula or CSF-venous fistulas not associated with an epidural leak.
Aquifer testIn hydrogeology, an aquifer test (or a pumping test) is conducted to evaluate an aquifer by "stimulating" the aquifer through constant pumping, and observing the aquifer's "response" (drawdown) in observation wells. Aquifer testing is a common tool that hydrogeologists use to characterize a system of aquifers, aquitards and flow system boundaries. A slug test is a variation on the typical aquifer test where an instantaneous change (increase or decrease) is made, and the effects are observed in the same well.
Permeability (Earth sciences)Permeability in fluid mechanics and the Earth sciences (commonly symbolized as k) is a measure of the ability of a porous material (often, a rock or an unconsolidated material) to allow fluids to pass through it. Permeability is a property of porous materials that is an indication of the ability for fluids (gas or liquid) to flow through them. Fluids can more easily flow through a material with high permeability than one with low permeability.
Hydraulic conductivityIn science and engineering, hydraulic conductivity (K, in SI units of meters per second), is a property of porous materials, soils and rocks, that describes the ease with which a fluid (usually water) can move through the pore space, or fractures network. It depends on the intrinsic permeability (k, unit: m^2) of the material, the degree of saturation, and on the density and viscosity of the fluid. Saturated hydraulic conductivity, Ksat, describes water movement through saturated media.
Groundwater flow equationUsed in hydrogeology, the groundwater flow equation is the mathematical relationship which is used to describe the flow of groundwater through an aquifer. The transient flow of groundwater is described by a form of the diffusion equation, similar to that used in heat transfer to describe the flow of heat in a solid (heat conduction). The steady-state flow of groundwater is described by a form of the Laplace equation, which is a form of potential flow and has analogs in numerous fields.
Clastic rockClastic rocks are composed of fragments, or clasts, of pre-existing minerals and rock. A clast is a fragment of geological detritus, chunks, and smaller grains of rock broken off other rocks by physical weathering. Geologists use the term clastic to refer to sedimentary rocks and particles in sediment transport, whether in suspension or as bed load, and in sediment deposits. Clastic sedimentary rocks are rocks composed predominantly of broken pieces or clasts of older weathered and eroded rocks.
Plant propagationPlant propagation is the process by which new plants grow from a various sources, including seeds, cuttings, and other plant parts. Plant propagation can also refer to the man-made or natural dispersal of seeds. Propagation typically occurs as a step in the overall cycle of plant growth. For seeds, it happens after ripening and dispersal; for vegetative parts, it happens after detachment or pruning; for asexually-reproducing plants, such as strawberry, it happens as the new plant develops from existing parts.
Composite materialA composite material (also called a composition material or shortened to composite, which is the common name) is a material which is produced from two or more constituent materials. These constituent materials have notably dissimilar chemical or physical properties and are merged to create a material with properties unlike the individual elements. Within the finished structure, the individual elements remain separate and distinct, distinguishing composites from mixtures and solid solutions.
WikiLeaksWikiLeaks (ˈwɪkiliːks) is a publisher and media organisation founded in 2006. It operates as a non-profit and is funded by donations and media partnerships. It has published classified documents and other media provided by anonymous sources. It was founded by Julian Assange, an Australian editor, publisher, and activist, who is currently challenging extradition to the United States over his work with WikiLeaks. Since September 2018, Kristinn Hrafnsson has served as its editor-in-chief.
HydrogeologyHydrogeology (hydro- meaning water, and -geology meaning the study of the Earth) is the area of geology that deals with the distribution and movement of groundwater in the soil and rocks of the Earth's crust (commonly in aquifers). The terms groundwater hydrology, geohydrology, and hydrogeology are often used interchangeably. Hydrogeology is the study of the laws governing the movement of subterranean water, the mechanical, chemical, and thermal interaction of this water with the porous solid, and the transport of energy, chemical constituents, and particulate matter by flow (Domenico and Schwartz, 1998).
Source rockIn petroleum geology, source rock is rock which has generated hydrocarbons or which could generate hydrocarbons. Source rocks are one of the necessary elements of a working petroleum system. They are organic-rich sediments that may have been deposited in a variety of environments including deep water marine, lacustrine and deltaic. Oil shale can be regarded as an organic-rich but immature source rock from which little or no oil has been generated and expelled.
