Clay compaction method

Some groundworkers that we are working with have been tasked with filling an old basement with reworked clay from our site. Their specification requires 175mm layers with 4 passes of a their weight of vibratory roller. They however are doing 350mm layers with 8 passes.

My question is, is there a direct correlation with thickness/passes, or shoud they be doing more passes?


When a contractor proposed an alternate approach to achieving compaction, I’ll query about their method to see what it is, if they’ve used it before, and did they achieve the degree of compaction? Finally, was there any testing performed to confirm the compaction had been achieved.

If they want to use thick lifts (+8 inch loose with heavy equipment, +4 inch with manually operated equipment), I’ll tell them it is their option to try it and demonstrate the effort will work. This means 1) watching them perform the work and then 2) testing at variable elevations in the compacted lift to confirm they’ve achieved the desired result. This lets me develop a reasonable expectation of production time, as well as verify what operation they will use (this is useful in determining if they’ve really used the method which has been tested for).

And, I’ll let them know if it doesn’t provide the result required in the specs, they’ll need to redo it.

Above is a snippet.