Angle of repose definition

Any material of a granular nature, even when the individual units are very large, like chunks of broken concrete or boulder sized rocks, naturally forms a pile in the shape of a cone when deposited on a flat surface from a height. The natural profile of this cone will approximate the angle of repose for that particular material or mixture. Very small or smooth granules that exert little friction on each other will tend to form piles with shallower sides. Rougher granules or those that adhere to each other strongly tend to form piles with steeper sides and a higher angle. Angle of repose is a term used to describe the maximum angle at which a pile of granular material will remain stable without any of the material sliding downward. Geologists, as well as mining and civil engineers, often use this measurement to analyze slopes and embankments for danger of collapse as well as helping to evaluate potential danger of avalanche. It is useful in designing storage and transportation machinery for granular materials as it can give an engineer insight into the appropriate size and shape of such devices. Civil engineers use the data when designing and managing construction and land management projects, such as levees, dams, and raised roadbeds. Geologists and vulcanologists use it to predict the possible behavior of cinder cones and sand volcanoes, as well as to study processes related to the weathering of rocks and deposition of sediments. Engineers and scientists use a number of m...

Key concepts Physics Gravity Forces Angle of repose Introduction Have you ever seen video footage of an avalanche or landslide rolling down a hill? Why is it that at one moment everything seems fine then suddenly the mountain begins to slump? This movement has something to do with how the snow or soil is piled up on the mountain. Granular materials such as snow or soil generally pile up relatively well. If the slope angle gets too steep, however, the materials will start to slide down the slope. This critical slope angle, also called the angle of repose, is different for different materials. In this activity you will create your own small avalanches and determine the angle of repose for different materials along the way! Background If you pour a granular material on a flat surface, it will form a conical pile. If you add more of the material, the pile will grow. At some point, however, the slope angle of the pile will always stay the same. This is because as the pile grows and its slope reaches a certain angle, some material will slide down the pile. This is the angle of repose and is the steepest angle at which a material can be heaped without sliding down. But why would the material slide? The reason is gravity. The gravitational force acting on the material on the slope can be split into two different components: One, the normal force, pulls the material into the slope in a direction perpendicular to the slope surface. The normal force pulls inward on the grains on the ...

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Angle of Repose The angle of repose—the angle between the slope of the pile and the horizontal—correlates with the strength of particle-particle interactions and, therefore, is measured to infer flowability. From: Handbook of Pharmaceutical Wet Granulation, 2019 Related terms: • Lactose • Bulk Density • Tapped Density • Powder Flow • Hausner Ratio The angle of repose ( Fig. 7) is a parameter commonly used for the evaluation of interparticle force. 16 The simplest method for the determination of the angle of repose is the “poured” angle. A funnel with a wide outlet is affixed at a distance of 10 cm above the bench, where a piece of paper is placed directly beneath the funnel. Powder is added while the funnel is closed. The contents flow through and collect on the paper. The diameter of the cone ( D) and two opposite sides ( l 1 + l 2) are measured with rulers. The angle of repose (θ) is calculated from the equation arc cos[ D/( l 1 + l 2)]. The relationship between flow properties and angle of repose has been established. When the angle of repose is less than 25 degrees, the flow is said to be excellent; on the other hand, if the angle of repose is more than 40 degrees, the flow is considered to be poor. G.E. Amidon, ... D.M. Mudie, in Developing Solid Oral Dosage Forms (Second Edition), 2017 10.3.2.2Angle of repose and flow through an orifice The angle of repose has long been used to characterize bulk solids. 28–30 Angle of repose is a characteristic related to interpartic...