Dynamic Cone Penetrometer (DCP)

The LabQuip Dynamic Cone Penetrometer (DCP) is an instrument designed for the rapid in-situ measurement of the structural properties of existing road pavements constructed of unbound materials. The robust and simple design means that the DCP is quick and easy to use, portable and suitable for use in locations where access may be difficult.

Correlations have been established between measurements with the DCP and conventional in-situ CBR so that results can be interpreted and compared with CBR specifications for pavement design. A typical test takes only a few minutes and therefore the instrument provides a very efficient method of obtaining information which would normally require the digging of test pits.

Method of use

The 8 kg free fall hammer is lifted and dropped through a height of 575mm. The distance pf penetration of the cone tip is then recorded and the cycle repeated. Continuous measurements can be made down to a depth of approx 850mm or when extension shafts are fitted to a maximum recommended depth of 2 metres. Where sub-pavement layers have different strengths, the boundries can be identified and the thickness determined.

  • Case size approx. 1100x250x150mm
  • Weight 22kg
  • Well proven, robust design
  • Portable and easy to operate
  • Tests can be carried out in minutes
  • Results correlate well with conventional CBR readings
  • Detects layer boundaries and thicknesses
  • Ideal in locations where access is difficult (such as coal holes)

The Dynamic Cone Penetrometer is a long steel rod with a standard size hardened steel cone at the penetrating end. Its length is approximately two metres, but it can be extended by extension rods. At upper end of the steel bar is a captive weight surrounding the rod, this weight is able to fall freely through a given drop height to achieve a standard amount of penetrative effort at every drop. By measuring the penetration of the cone against number of drops of the weight it is possible to plot resistance to penetration and indirectly the strength / compaction of the layer being tested. This equipment is very useful for testing fill compaction, especially in trench reinstatement, performed with care. It is possible to obtain an approximate CBR figure from the results of using this equipment by applying a simple formula.  It is a guide figure but still useful to know.

The Basic CBR Test

The California Bearing Ratio, believe it or not, was developed by The California State Highways Department. It is in essence a simple penetration test developed to evaluate the strength of road subgrades.

This consists of causing a plunger of standard area to penetrate a soil sample, (this can be in the laboratory or on site). The force (load) required to cause the penetration is plotted against measured penetration, the readings noted at regular time intervals. This information is plotted on a standard graph, and the plot of the test data will establish the CBR result of the soil tested. The test is fully covered in :- BS 1377 : Soils for civil engineering purposes : Part 4,Compaction related tests.

Reason For CBR Test

It sounds complicated, but the basis behind it is quite simple. We are determining the resistance of the subgrade, (i.e. the layer of naturally occurring material upon which the road is built), to deformation under the load from vehicle wheels. Even more simply put, 'How strong is the ground upon which we are going to build the road'.

THE CBR TEST IS A WAY OF PUTTING A FIGURE ON THIS INHERENT STRENGTH, THE TEST IS DONE IN A STANDARD MANNER SO WE ARE ABLE TO COMPARE THE STRENGTHS OF DIFFERENT SUBGRADE MATERIALS, AND WE ARE ABLE TO USE THESE FIGURES AS A MEANS OF DESIGNING THE ROAD PAVEMENT REQUIRED FOR A PARTICULAR STRENGTH OF SUBGRADE.

The stronger the subgrade (the higher the CBR reading ) the less thick it is necessary to design and construct the road pavement, this gives a considerable cost saving.

We can also supply spares and repair your DCP.

LabQuipLabQuip Ltd. The Black Barn, White Ox, Scotland Road,Penrith, Cumbria. CA11 9NQ
Tel: 01768 895080

CA11 9NQ
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