Proctor compaction test

The Proctor () is a term from geotechnical engineering, civil engineering and geology and is the highest achievable under a defined compression work density of a soil which is established in the standardized test ( Proctor test according to DIN 18127 ) at optimum water content. However, it is not always the highest density that can occupy a floor; however, this is often mistaken as accepted or formulated.

The Proctor test was introduced in August 1933 by the American Civil Ralph R. Proctor.

The remaining decrease of the pore share or permanent increase in the dry density of a soil is called compaction. Here, a full saturation is hardly achieved and the dry density remains below the saturation line. The dry density, which is achieved at a predetermined floor, is dependent not only on the water content of the work by a specific work of compression and compression mode.

Proctor

One soil sample, the dry density ρd was previously determined, is in a defined vessel ( or Proctor Proctor Compactor ) according to an established work procedures supplied predefined power over a Proctorverdichter ( drop weight with Führungs-/Griffstange ) and then determines the density achieved. The experiment is carried out at least five times with different water contents. It now carries the densities obtained using the corresponding water content, results in a curve that first increases, reaches a maximum and then decreases again. The maximum of this curve is the Proctor density of the soil with the corresponding optimum water content. Here, a clear correlation between compressibility and water content is visible.

The degree of compression can be expressed as follows:

The degree of compaction is thus given as a percentage of the maximum possible at the Proctor density. It serves as a reference value for the bulk density, which can be achieved on a building site, or has reached. By compared with the standard Proctor compaction performance also increased Proctordichten of over 100 % are achievable. Is often - in dependence of the type of soil - a compression ratio required by at least 95%. The degree of compaction required in earthworks are (Additional technical terms of contract and guidelines for earthworks in road construction ) specified in the rest of the ZTVE -StB.

The purpose of this test method is the proportion of the third phase ( air) to reduce the three-phase system of soil (air, water, solids ) to a minimum. This happens during compaction by reducing the pore space by " pushed together ( compression ) " of the solid particles and filling the remaining pore water ( steady increase of the water content ). The increase in the dry density by water content increase also resulted from a significant reduction of the frictional forces between the solid particles - the water acts as a kind of " lubricant", so that the fixed, constant compaction energy better effect at higher water contents. This effect flips once the optimum water content is exceeded and an unfavorably high water content is reached. The introduced compaction energy then no longer acts in a denser deposition of the grains, but is included in the excess amount of water, so that leaking or splashing out during compaction water.

Experimental setup and sample

A gravel (up to 10 mm grain size ) is sequentially examined with 6, 7, 8, 9, 10 and 11 % water content. In each case, about 2 kg of soil are filled in three layers in the specified cylinder of 10 cm diameter. Each layer is compacted with 25 blows of a 2.5kg rammer of 5 cm diameter 30 cm drop height. For each sample, the dry density (ratio of dry weight and volume) in a graph (x-axis = water content in%, y -axis = calculated dry density in t / m or g / cc) is then calculated and recorded. This results in the optimum water content for compaction; the maximum dry density, in a gravel eg at 2.12 t / m³ ( g / cc) and the water content of around 7 %.