The Clegg Impact Soil Tester manufactured by SDi provides a means for measuring and controlling soil strength and consolidation levels during trench re-instatement.
It is also used to confirm uniform compaction of over wide areas of ground, identifying poorly compacted areas and ineffective rolling of materials. The most popular Clegg instrument is one using a 4.5 Kg hammer.
Lightweight versions of the Tester available in 0.5 Kg and also 2.25 Kg weights are manufactured by SDi and are suitable for sports turfs whilst a heavy duty version is supplied for testing harder materials and roadworks.
The Tester consists of a compaction hammer operating within a vertical guide tube. When the hammer is released from a fixed height it falls through the tube and strikes the surface under test, decelerating at a rate determined by the stiffness of the material within the region of impact. A precision accelerometer mounted on the hammer feeds its output to a hand held digital readout unit which registers the deceleration in units of Impact Value (IV). The IV indicates soil strength and shows good correlation with CBR test results.
The Clegg Impact Soil Tester is manufactured and marketed by SDi of Trowbridge under an exclusive licence from Dr Baden Clegg Pty Ltd, the Australian Inventors.
Test procedure with the 4.5 kg Clegg