Any description of a material would be incomplete without consideration of the physical properties of that material. For materials that exist as particles in a bulk, the properties of the bulk material are often as important as properties of the individual particles, and perhaps the most basic bulk property is that of bulk density. This is simply defined as the mass of a bulk material divided by the volume that the mass occupies.
The first problem of characterizing the bulk density of compressible materials is how to obtain a value at any location in a pile. This invariably involves disturbing the sample to some extent, or disturbing the surrounding material so that the load on the sample is changed, or both. This paper describes an alternative approach in which the loading at any depth in the bulk is simulated to obtain a relationship between depth and bulk density. This relationship can then be used to derive a value for the effective bulk density of the entire mass of
material.
The objective was to develop a laboratory method of characterizing bulk density that was cheap, simple, precise, and accurate. Since it has the potential to be applied to a wide range of materials, the approach was tested with compost, wood shavings, straw, and peat moss.