: Measures the vertical strain (swell or settlement) under a specific vertical stress representing field conditions (e.g., overburden pressure).
Alternatively, in a variation of this test, the sample is wetted immediately, and the operator continually increases the vertical load to strictly prevent the sample from expanding. Astm D4546-21 Pdf
If you're interested in accessing the full text of ASTM D4546-21, I recommend: : Measures the vertical strain (swell or settlement)