Bulk density

Short description: Mass per unit volume of granular matter

In materials science, bulk density, also called apparent density or volumetric density, is a property of powders, granules, and other "divided" solids, especially used in reference to mineral components (soil, gravel), chemical substances, pharmaceutical ingredients, foodstuff, or any other masses of corpuscular or particulate matter (particles).

Bulk density is defined as the mass of the many particles of the material divided by the total volume they occupy. The total volume includes particle volume, inter-particle void volume, and internal pore volume.[1]

Bulk density is not an intrinsic property of a material; it can change depending on how the material is handled. For example, a powder poured into 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" (or "poured" density) 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.[2])

In contrast, particle density is an intrinsic property of the solid and does not include the volume for voids between particles.

## Contents

* 1 Soil
* 2 See also
* 3 Notes
* 4 External links

## Soil

The bulk density of soil depends greatly on the mineral make up of soil and the degree of compaction.[3] The density of quartz is around 2.65 g/cm3 but the (dry) bulk density of a mineral soil is normally about half that density, between 1.0 and 1.6 g/cm3. In contrast, soils rich in soil organic carbon and some friable clays tend to have lower bulk densities (<1.0 g/cm3) due to a combination of the low-density of the organic materials themselves and increased porosity. For instance, peat soils have bulk densities from 0.02 to 0.98 g/cm3.[4]

Bulk density of soil is usually determined from a core sample which is taken by driving a metal corer into the soil at the desired depth and horizon.[5] This gives a soil sample of known total volume, Vt. From this sample the wet bulk density and the dry bulk density can be determined.[6]

For the wet bulk density (total bulk density) this sample is weighed, giving the mass Mt. For the dry bulk density, the sample is oven dried and weighed, giving the mass of soil solids, Ms. The relationship between these two masses is Mt = Ms \+ Ml, where Ml is the mass of substances lost on oven drying (often, mostly water). The dry and wet bulk densities are calculated as

Dry bulk density = mass of soil/ volume as a whole

ρb=MsVt

Wet bulk density = mass of soil plus liquids/ volume as a whole

ρt=MtVt

The dry bulk density of a soil is inversely related to the porosity of the same soil: the more pore space in a soil the lower the value for bulk density. Bulk density of a region in the interior of the earth is also related to the seismic velocity of waves travelling through it: for P-waves, this has been quantified with Gardner's relation. The higher the density, the faster the velocity.

## See also

* Brazil nut effect
* Characterisation of pore space in soil
* Effective porosity
* Density meter
* Number density

## Notes

1. ↑ Buckman, Harry O.; Brady, Nyle C. (1960). The Nature and Property of Soils - A College Text of Edaphology (6th ed.). New York City: Macmillan. p. 50.
2. ↑ "Powder Bulk Density - Bulk Solids density - Bulk Powder Properties - Powder Loose Density - Powder tapped density - PowderProcess.net" (in en). http://www.powderprocess.net/bulk_density.html.
3. ↑ Soil compaction impact and modelling. A review
4. ↑ Soane, B.D. (1990). "The role of organic matter in soil compactibility: A review of some practical aspects" (in en). Soil and Tillage Research 16 (1–2): 179–201. doi:10.1016/0167-1987(90)90029-D.
5. ↑ USDA Natural Resources Conservation Service "Soil quality indicators -- Bulk density" retrieved December 5, 2013
6. ↑ Argonne National Lab "RESRAD Data collection handbook, chapter 2 -- Soil density" retrieved May 26, 2012

## External links

* University of Leicester podcast 'How to measure dry bulk density'
* Bulk density calculator
* 'Determination of bulk density'

* v
* t
* e

Geotechnical engineering

Investigation|

| In situ|

* Cone penetration test
* Standard penetration test
* Groundwater monitoring
* Well
* Piezometer
* Borehole
* Crosshole sonic logging
* Nuclear densometer test
* Static load testing
* Trial pit
* Exploration geophysics

|

Laboratory|

* Atterberg limits
* California bearing ratio
* Direct shear test
* Hydrometer
* Proctor compaction test
* R-value
* Sieve analysis
* Triaxial shear test
* Hydraulic conductivity tests
* Water content tests

Soil|

| Materials|

* Clay
* Silt
* Sand
* Gravel
* Peat
* Permafrost
* Loam
* Loess

|

Properties|

* Soil classification
* Hydraulic conductivity
* Water content
* Void ratio
* Bulk density
* Thixotropy
* Reynolds' dilatancy
* Angle of repose
* Cohesion
* Porosity
* Permeability
* Specific storage

Mechanics|

* Effective stress
* Pore water pressure
* Shear strength
* Overburden pressure
* Consolidation
* Compaction
* Shear wave
* Lateral earth pressure

Foundations|

* Shallow
* Deep
* Bearing capacity
* Dynamic load testing
* Pile integrity test
* Wave equation analysis
* Statnamic load test

Retaining walls|

* Gabion
* Ground freezing
* Mechanically stabilized earth
* Pressure grouting
* Slurry wall
* Soil nailing
* Tieback

Stability|

* Slope
* analysis
* mass wasting
* landslide
* Deformation monitoring
* automated

Earthquakes|

* Soil liquefaction
* Response spectrum
* Seismic hazard
* Ground–structure interaction

Geosynthetics|

* Geotextile
* Geomembrane
* Geosynthetic clay liner
* Cellular confinement

Numerical analysis|

* SEEP2D
* STABL
* SVFlux
* SVSlope
* UTEXAS

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