Getting the correct soil compaction during streetworks reinstatements is not always easy, undeniably important though it is. According to the Local Government Association 60% of road reinstatements are currently failing nationwide.
And a high proportion of these failures is due to poor compaction.
The normal method for testing compaction is to use a nuclear density gauge, but this requires special training as it presents a risk of exposure to radiation. French consultant Soil Solution has developed the Panda, an instrumented cone penetrometer system which is particularly suited for use in trenches. Light and portable, and operated by one person, the device measures the force required to drive a small cone manually up to 6m into the ground using an 2kg hammer.
The driving force is measured using an accelerometer and converted to give a measure of soil resistance. This is used to determine whether the soil has passed or failed the specified compaction specification using a database of soil types built into the Panda's Windows software.
In contrast to drop weight cone penetrometers, the Panda's use of a hammer means that variable blow energy is available. This means it can be driven rapidly through hard ground - and may be driven horizontally into trench walls if required.