- Bulk density
Bulk density is a property of powders, granules and other "divided" solids, especially used in reference to
soil. It is defined as the massof many particles of the material divided by the total volumethey occupy. The total volume includes particle volume, inter-particle void volume and internal pore volume. [Page 50 in Citation
last = Buckman | first = Harry O. | last2 = Brady | first2 = Nyle C. | title = The Nature and Property of Soils - A College Text of Edaphology | place = New York | publisher = MacMillan Publishers, New York, NY | year = 1960 | edition = 6th]
densityis not an intrinsic property of a material; it can change depending on how the material is handled. For example, a powder poured in to a cylinder will have a particular bulk density; if the cylinder is disturbed, the powder particles will move and usually settle closer together, resulting in a higher bulk density. For this reason, the bulk density of powders is usually reported both as "freely settled" and "tapped" density (where the tapped density refers to the bulk density of the powder after a specified compaction process, usually involving vibration of the container.)
bulk densityof soil depends greatly on the mineral make up of soil and the degree of compaction. The density of quartzis around 2.65g/cm³ but the bulk density of a mineral soil is normally about half that density, between 1.0 and 1.6g/cm³. Soils high in organics and some friable clay may have a bulk density well below 1g/cm³
Bulk density of soil is usually determined on
Core samples which are taken by driving a metal corer into the soil at the desired depth and horizon. The samples are then oven dried and weighed.
Bulk density = mass of oven dry soil/core volume
The bulk density of soil is inversely related to the
porosityof the same soil. The more pore space in a soil the lower the value for bulk density.
Brazil nut effect
Characterisation of pore space in soil
Wikimedia Foundation. 2010.