Max Ground Pressure / Bearing Capacity
Max Ground Pressure / Bearing Capacity
(OP)
I'm jacking up a large electric mining shovel (1.5m lbs) and am wondering what a safe bearing capacity would be?
The pad is built out of 3-4" rock with a layer of compacted 3/4" crush on top.
The pad is built out of 3-4" rock with a layer of compacted 3/4" crush on top.





RE: Max Ground Pressure / Bearing Capacity
RE: Max Ground Pressure / Bearing Capacity
RE: Max Ground Pressure / Bearing Capacity
Look to the footing dimensions and reinforcing, if known, to get a bearing approximation, which may be lower for an isolated as opposed to strip condition.
Mike McCann
MMC Engineering
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RE: Max Ground Pressure / Bearing Capacity
However the coarse quality of the rock base may mean some tilt may happen. To forestall this I would try to (jack?) brace the machine against sidewise displacement.
RE: Max Ground Pressure / Bearing Capacity
3-4" is 3 feet
3/4" is 1 foot
Under the pad is rock (see picture)
Yah i know the ground pressure exerted by the tracks (48.9 psi) but i dont want to have to put that much cribbing under my jacks b/c we need to be able to work in there.
In the first picture the shovel is on the pad (no concrete)
RE: Max Ground Pressure / Bearing Capacity
RE: Max Ground Pressure / Bearing Capacity
If, as you jack, you see displacement, just increase the bearing area and try again. Displacement of your granular mat is likely to be instantaneous or near that. I'd keep the mat as thin as possible, since you have rock below.
Then, once you find the situation does not move, at each support, you supplement it with say 50 percent added area support nearby each main support.
Consider what is safe when working under a car. You don't depend on any hydraulic other mechanical lift, but supplement with jack stands. Do the same here.