Assessing the level of compaction of sub-surface soils can be essential to designing and validating compaction, particularly those subject to transient or cycling loads. A perfect example is roadways.
If the soil beneath a roadway is not compacted sufficiently, then over time the cycling loads of passing traffic will compact the soil further, leading to surface failures such as large cracks, potholes, and displaced pavement. Assessing the compaction of non-cohesive soils such as fine sands is a particularly difficult challenge.
As we’ve noted in other blog posts, removing a sample from the ground and sending it to a lab is not only time consuming and expensive, but can be highly inaccurate in non-cohesive soils because the samples by necessity are disturbed from their sub-surface condition.
One alternative to soil extraction is Nuclear Density testing. Nuclear Density testing requires a radiation source such as Cesium or Radium. The instrument emits a beam of particles that either are reflected back or pass through sediments being tested for density. Using a calibrated density gauge can provide results through a variety of different materials, including varied deposition soils or road sub-base.
While Nuclear Density testing is relatively efficient because it uses radioactive materials, operators must be specially trained and licensed. It is also riskier to manage at a worksite.
This is where dynamic cone penetration (DCP) testing comes in. The DCP test gathers simple in-situ soil characteristics that are designed to assess soil density, load bearing capacity and shear strength. Common applications for DCP testing include residential and commercial concrete and foundation leveling, airfield and highway construction, and embankment stabilization.
A manual or automated DCP uses a 60-degree conical tip cone or drive point as the resistive surface. Dual mass DCPs utilize a known weight which is dropped from a consistent height transferring energy through the instrument. The number of blows to penetrate the soil and progressing depth measurements can provide an in-situ density during field testing.
Vertek’s Smart DCP Kit gives users the ability to conduct three times the number of tests compared to standard DCP testing. Dynamic cone penetration can provide a density stratigraphy to beyond 3 feet and is safer and less complicated to administer than Nuclear Density testing.
The adaptive Smart DCP Kit components and free mobile app can display continuous measurement data with each blow (>or<4mm) depth increments as the DCP is driven into the subsurface. Each test’s recorded data is easily saved and shared after each penetration location is completed. Users report that the Smart DCP Kit provides the advantage of identifying a subsurface weakness and the results of the stabilization effort.
While DCP results will be consistent for most soil conditions, it is recommended that the field tests be reviewed in soft sediments to ensure that data interpretation is accurate.
To learn more about DCP testing and Vertek’s DCP products, give us a call at 1-800-639-6315 or contact us today.