# Spongey / springy earth after filling in trench



## wallmaxx (Jun 18, 2007)

I know wood. Framing......easy peasy.

Earthworks.........not so much.

A good friend of mine has dug some 24" deep trenches for utility expansion and once inspected, he filled them in. He then used a compacting machine (like a gas-powered pogo stick - I don't know the industry term)

Well, the soil is a mix of clay, rocks sand and top soil. it was wet when it went back in the trench.

Fat forward a week, and he called me today to ask if I knew why the ground he tamped down in the trench area was springy? He says it gives about 1".

I'm thinking that the wet earth is trapped under the dried out top layer, but what do I know.

He's willing to rent the mini ex again and dig it up and add lime or replace it with different medium. Any thoughts/suggestions?


----------



## CrpntrFrk (Oct 25, 2008)

Yes, too wet. The soil should be damp enough to clump together. If it is too wet, it will pump. You'll have to dig it up and try again. 

When you dig it up, mix all the soil together and see where you are at with moisture content. You should be able to pick up some soil in your hand and make a clump by squeezing. If you have slimy mud on your hand it is too wet. 

When filling back in you should be able to do 12" lifts of soil then compact with a jumping jack. You should be able to stand on a spade shovel after compaction and the shovel only go in about an inch or so if compacted correctly.


----------



## Morning Wood (Jan 12, 2008)

I'd use a plate compactor instead


----------



## jhark123 (Aug 26, 2008)

If there is paving going in over this trench he should replace the fill with 5/8minus


----------



## griz (Nov 26, 2009)

We don't usually put native soils back in the ditch.

3/4- in lifts or CDF.


----------



## slowsol (Aug 27, 2005)

Agreed, it was too wet. Depending on the size of the trenches, I'd fill with premium fill. We would use 57's in this area. Essentially small, self compacting stone.


----------



## wallmaxx (Jun 18, 2007)

Thanks for the education. 
Y'all are great. 
I'll pass this along.


----------



## dayexco (Mar 4, 2006)

griz said:


> We don't usually put native soils back in the ditch.
> 
> 3/4- in lifts or CDF.


dissimilar soils in an area that has extreme freeze/thaw areas...like here, that does NOT work. your granular/stone backfill, stays put, native soils around it....freeze/expand...leaving a divot every freeze period until the surrounding soils thaw and contract in the spring.

best thing is go by the soils report. adhere to the optimum moisture content in the soil. if what's excavated is too wet? haul it away and go find some very similar soils that are at optimum, or a touch below moisture wise...and compact it in.


----------



## mattg2448 (Jan 26, 2015)

Sand is our normal back fill material.. depending where it comes from it packs very nicely


----------



## rustyjames (Aug 28, 2008)

Here we typically use what came out of the excavation (without the topsoil) for backfilling. It's compacted in lifts, and lift depth depends on the type of compaction equipment being used. It can be quite expensive, and unnecessary filling an excavation with stone.


----------



## Powerjoke (Nov 23, 2015)

I know it's a bit of an old thread but here it goes anyways, I hate for my first post to sound like I'm arguing with everyone but the mist of it is vibration is your enemy with wet material.

If there's utilities in the trench they'll call for granular or flowable fill most of the times, if there is nothing in the trench and it's still spongy dig it out throw some gabion in it let it jaw together and most importantly if you have wet soil DO NOT VIBRATE it'll just make it worse and worse with every pass, 

I've had spots like your talking about start a trench wide and before it's over have to dig it out with loader and waste several loads of 4-6" all because of trying to work wet ground and vibrating.

Pj


----------



## rino1494 (Jan 31, 2006)

Where is this at ? On his own property in his yard or on a customers property. If it his own in the yard that will not see any heavy traffic, then just leave it be. It eventually will dry out.


----------



## Railman (Jan 19, 2008)

It's spongy because air got pumped into the wet dirt, creating a gazzillion litle air pockets in the wet dirt. Eventually, rain pounding will usually work the air out. If not, I'd try a soaker hose.


----------



## Hierr (Nov 26, 2015)

Am I the only one that saw that he backfilled it with one 24" lift of wet material and then hit it with a Wacker and said all good.

Better check the Geotech report and import some engineered fill. Anybody seen my 320 with the Sheepsfoot roller.

/Sarcasm off. Sorry gonna have to dig it back up. Be careful if it's direct buried. Be careful if its in pipe/conduit. Now spread out the material and let it dry out some, then backfill it in about 6" layers (Lifts) max, compact with the wacker, another lift, compact, etc. You need to have some moisture to get compaction, but without getting a tester to come take some samples and cook em to figure out optimum you can get it better than it is now. Now I wouldn't build a structure over it without getting the compaction tested.


----------



## dayexco (Mar 4, 2006)

Right soils, 95℅ standard density is easily attainable with ex mounted sheepsfoot or vibe plate.

Sent from my CMP749 using Tapatalk


----------



## dayexco (Mar 4, 2006)

I should have added to post "24 inch" lifts

Sent from my CMP749 using Tapatalk


----------



## AndyStandy (Dec 10, 2015)

Also worth noting - if you are backfilling with native material, don't let any organic material get mixed into your pile you are excavating - put it to the side, otherwise if it ends up back in your trench you will have issues from the start - if the material coming out is wet, spread it out and let it dry out. If you are paving over it, import an engineered fill.


----------

