Well here is something to think about I was pumping a new large house it was the 2nd one of the day I was set up-part on road- part on dirt this ground was as hard as nails or so I thought I was flat boomed out under low voltage lines then crack and the rear of the truck dropped I had 11 4x4 set up under that rear out rigger and I broke through 7 of them. The gound collapsed only under that outrigger you could see the hole. If I did not overload the dunnage my nice pump would have gone over ....for sure. I am sorry no photos but what a weird hole and only directly under the the leg....

I can't remember a job where I didn't have to use dunnnage at some extent....It only takes a few extra minutes to put out, but it can really relieve stress on ya, and of course prevent the possibility of a disaster. [IMG]http://i148.photobucket.com/albums/s39/mattandveca/ReedST36026.jpg[/IMG]

Glad all ended up ok, were you 17 away from the power lines?

Yeah,those are scary things to happend.It has happend to me and many others here as well.I always looked over my shoulder to see who was helping me.Had that happend running a 52m,flat boomed over that outrigger.I was on railroad ties,I never asked why but knew I had help that day.

That story makes a pretty valid case for dunnage use.

One thing that too many operators don’t take into consideration is the strength of the individual pieces of dunnage. It is true that if you use several bits of jobsite dimension lumber; 2x6, 2x10, whatever, that you may lower the ground pressure under your outrigger…….

The larger problem is; what happens if/when, as in this case, the ground below your outrigger has a void? If the individual bits are not capable of supporting the load – across – the void; then your pump still falls over! Stacking 2x material is never as strong as using a 4x or 6x. Individual pieces used in tandem do not equal one piece equal to their combined dimension.

In my mind; the smallest dimension suitable for pump shoring is a 4x6. 6x6 material is even better. All things being equal, my personal choice is an oak 4x6. The material make-up its self is also important. Job site, pine 4x4s are great for shoring up a deck, but not much good for dunnage on a pump unless you increase the dimension of the pad, and cross the 4x4s with another layer of 4x4s. Pine is fine for building a house, not a bridge.

The above information is my personal opinion based on years of doing, watching, asking. My way has worked for me 100% of the time……… If you want a more educated opinion (and I do suggest that you get one) ask an engineer.

For a guarantee, use plate steel or crane pads. ;~)

Typical 36 meter outrigger down-force 38,000#

Down-force (soil pressure) with 2'x2' factory pad = 66#psi

Down-force (soil pressure) with 4'x4' oak dunnage= 16#psi

ACPA SOIL LOADING - UNKNOWN DIRT = 22#psi

which boom would you rather work under?

every pump we have has 12-14 4x6x4' on the truck at all times,you cant rely on the every jobsite to have necessary dunnage,we make sure our trucks have them and we inspect for cracking and breakage frequently,and we still have had a tipping incident with no one hurt or no damage to equipment,even with the dunnage put out you never know whats underground in this case it was underground utilities and the lot was fine graded with no tell tell signs of them being there except a electrical box about 100 ft down the road,we were very fortunate there wasn't any injuries.Unless your superman and have that x-ray vision you can never have enough dunnage.   

pudg

"Unless your superman and have that x-ray vision you can never have enough dunnage."

True story! Sounds like you & yours are doing all that can be done. ;~)

 Very good information Bob,that is interesting if you double the area of print you really lighten your bearing on the ground.I carry 15 oak boards about 4 feet long,I run a 32XL.

Bis,

It is being doubled both ways........ so it is really X 4

2x2=4   sq ft

4x4=16 sq ft