Big crane lifts on soft ground still bother me after 12 years

I've been running cranes since 2012 and I still get nervous when the mat starts sinking on a lift over 50 tons. Everyone tells me the ground bearing calculations check out, but I've seen too many pads tilt on jobsites in Houston where the soil looks fine on paper but turns out to be spongy underneath. Last year we did a 120 ton pick on a refinery job and the crane pad sunk 4 inches on one side even with two layers of mats. The site engineer said it was within limits, but I had to stop the lift for 20 minutes while they rechecked everything. Has anyone else had a situation where the math was right but your gut told you something was off? How do you handle that pushback from the project manager?

3 comments

3 Comments

the_jake2d ago

Oh man, I gotta disagree with you here. The numbers don't lie, and if the ground bearing calc said you were good, then you were good. Stopping a 120 ton pick for 20 minutes because you got a little spooked costs the client way more than the cost of a few extra mats. That sinking feeling is just you getting in your own head after a long career seeing close calls. The engineer ran the numbers with safety factors built in, probably 2:1 or 3:1 on the soil capacity, so that 4 inch sink is actually the ground settling and compacting just like it's supposed to. Project managers hate delays and if you stop every time the ground shifts a little, you gonna be out of a job real fast in this business. Trust the math, not your stomach.

emma_baker612d ago

Ain't that the truth? I had a 90 ton pick last month where the crane sunk a good 3 inches while we were walking, and the PM was screaming at me to keep going while I was about to have a heart attack.

johnson.river2d ago

Man, I gotta say your story is giving me flashbacks to what happened to my buddy Mark last year. He was doing a 60 ton pick in some marshy land in Louisiana and the crane started tilting like 2 degrees to the left. His PM was on the radio yelling at him to just finish the pick and he could feel the ground squishing under the outriggers like a sponge. He said he had to make a split second call and he just shut everything down and refused to move until they brought in more mats. Took three extra hours and the PM was FURIOUS but when they dug down later they found an old underground creek nobody knew about. Mark told me he still wakes up thinking about that day because if he'd listened to the PM it could have been real bad. So I feel you on not trusting the math when your gut is screaming at you and the ground is literally moving.