Search results
Results from the WOW.Com Content Network
The Bagnold formula, named after Ralph Alger Bagnold, relates the amount of sand moved by the wind to wind speed by saltation. It states that the mass transport of sand is proportional to the third power of the friction velocity. Under steady conditions, this implies that mass transport is proportional to the third power of the excess of the ...
Dilatancy of a sample of dense sand in simple shear. The phenomenon of dilatancy can be observed in a drained simple shear test on a sample of dense sand. In the initial stage of deformation, the volumetric strain decreases as the shear strain increases. But as the stress approaches its peak value, the volumetric strain starts to increase.
When the shear stress reaches a certain value, the force chains can break and the particles at the end of the chains on the surface begin to slide. Then, new force chains form until the shear stress is less than the critical value, and so the sandpile maintains a constant angle of repose. [7]
The Physics of Blown Sand and Desert Dunes is a scientific book written by Ralph A. Bagnold. [1] The book laid the foundations of the scientific investigation of the transport of sand by wind. [2] It also discusses the formation and movement of sand dunes in the Libyan Desert.
A group of hikers encountering quicksand on the banks of the Paria River, Utah Quicksand warning sign near Lower King Bridge, Western Australia. Quicksand is a shear thinning non-Newtonian fluid: when undisturbed, it often appears to be solid ("gel" form), but a less than 1% change in the stress on the quicksand will cause a sudden decrease in its viscosity ("sol" form).
The shear stress that works on the bottom (with a normal uniform flow along a slope) is: =, where: is the shear tension exerted by the flow on the bed; is the water depth; is the gradient (= the slope of the current).
The rectangularly-framed section has deformed into a parallelogram (shear strain), but the triangular roof trusses have resisted the shear stress and remain undeformed. In continuum mechanics, shearing refers to the occurrence of a shear strain, which is a deformation of a material substance in which parallel internal surfaces slide past one another.
The critical shear stress and also the critical Shields number (and ) describe the conditions when the sediment starts moving. Note that the shear stress is a property of the current, while the critical shear stress is a property of the sediment.