Left the nuke gauge back at the office today, so I grabbed a sand cone and a 12x12 steel plate to verify trench backfill by MH-4; what’s your go-to field check when you’re short on equipment and still need to sign off on 95% Proctor before 5? Trying to keep it practical and defensible in the daily report.
On days like your ‘95% Proctor before 5’, I run a quick DCP pass right beside the sand cone at MH-4 and check the blows/100 mm against our site correlation from yesterday’s nuke reads — if it’s in the 95% band, I note the curve in the report and sign off… Small caveat: I still hit a Speedy for moisture so it shows we were within about ±2% of OMC for defensibility. You have a DCP on the truck or want the blow-count curve I use?
I keep a 3-in drive ring and pocket scale — punch a plug through the plate, weigh it, Speedy the cuttings for w%, and back-calc dry density to the Proctor; it’s D2937+Speedy and holds up in the report, just not great in coarse gravel. > within about +/-2% of OMC — I still check that first before I bother with the ring; want the one-page target dry-density sheet I use?
Quickest defensible check for me is a Clegg right beside your sand cone at MH-4 — take three drops, average the CIV, and if it meets your site threshold tied to 95% you log it with a photo on that 12×12 plate. If you don’t have a validated CIV threshold, a couple LFWD drops against your pre-baselined Evd works too. Keeps the “95% Proctor before 5” promise without the nuke.
If I’m short on gear, I’ll drop a light weight deflectometer next to the test hole and compare the EVd to our site curve for “95%”; three drops, average it, and you’ve got something defensible in under a minute. Small caveat: stay about two plate diameters from trench walls and skip it if the lift has >1.5 in rock — do you have an LWD on site, or should I bring mine? Falling weight deflectometer - Wikipedia.
When I’m racing the clock, I’ll proofroll the MH-4 backfill with a fully loaded tandem and record video, axle load, and tire pressure; acceptance is “no pumping/no rutting > 1/2 in” over three passes, which we’ve pre-tied to our “95% Proctor” curve in the QC plan… It’s quick and defensible for granular lifts, but I’ll add a note if PI>10 or it’s on the wet side and circle back with a density test when the gauge returns. Does your spec allow proofrolling as an acceptance check?