Trench cave in impact Foundation forms.
Trench cave in impact Foundation forms.
(OP)
Trench cave in impact Foundation forms.
I have a cast in place foundation wall located 4' away from the edge of excavation which is a vertical cut 10' deep. OSHA wants the inner forms braced incase the soil gives way, and caves the forms in.
Obviously the best approach is to retain the soil in place. To accomplish this I suggested trench boxes between the forms and the soil then install braces on the inside of the forms. However, the contractor wants to avoid this if possible.
In the event that I do need to account for the dynamic load of the soil impact, can anyone give me some feed back what they've done in this situation.
I have a cast in place foundation wall located 4' away from the edge of excavation which is a vertical cut 10' deep. OSHA wants the inner forms braced incase the soil gives way, and caves the forms in.
Obviously the best approach is to retain the soil in place. To accomplish this I suggested trench boxes between the forms and the soil then install braces on the inside of the forms. However, the contractor wants to avoid this if possible.
In the event that I do need to account for the dynamic load of the soil impact, can anyone give me some feed back what they've done in this situation.





RE: Trench cave in impact Foundation forms.
I assume that the installed forms prevent installation of any type of cross bracing. I also assume that the excavation is wide and that there is not another excavated face to which you can cross brace. If so, then the most appropriate way to support the excavated in order to PROTECT THE WORKERS is to drive some cantilevered, steel sheet piling against the excavated face and sufficiently below the excavation subgrade. If the sheets can be driven, you can most likely drive the sheets without the need for workers to enter the unshored excavation. You might also be able to drive some cantilevered soldier beams and then drop in some timber lagging panels or steel plates to retain the soil between soldier beams. This won't be easy or cheap; but it can be done.
Your other (cheaper?) choice may be to excavate some more and safely slope back the 10' vertical cut to meet OSHA requirements.
Whether you install sheeting or do more excavation, you need to consider the effect of either method on any adjacent structures or utilities. This situation should have been addressed pre-bid and before any excavation was made. Contractors do stupid (yes, stupid) things like this every day and usually get away with it. Sometimes people get hurt or killed. You were just "unlucky" enough to get caught by OSHA.
RE: Trench cave in impact Foundation forms.
So the matter stands, and so building contractors get imaginative -they have the custom- on how avoid such major works. Fortunately dynamic contractors are overcoming such trend by embracing the safety in works, making a point from the start on using means thant ensure the safety of people and workers, and where in the past they would have accepted, say, a foundation made by shields or batches one besides another may well today ask themselves to do some pile, micropile or bentonite trench wall. They find at such instances also at those instances the incentive of a more expensive foundation where to mitigate any reduction of benefits they had to make in the bid process.
But of course safety anytime is paramount and we must help with our professional activity to it become custom. So much for if that makes the building more expensive; we are being pushed (I would say slowly, we can't, it seems, diggest and negotiate at a quicker pace both the stupid new nuisances from some codes and the true real betterments) toward better quality works. This enters the question on how a house or building is a one time shot, and hence even if made of industrial products rarely enough input is given to it the same quality levels that CAN (but not always is) given to industrial products made in the hundreds of thousands or even millions; and what the relative cost should and can be. But, even when our professions are in engagement with the economy of the works, our true task is in enabling the making of the works, i.e., in our task economy is only ancillary to design and construction, for there are others (owners, commissioners, construction planners, cost controllers, financial parties) that of themselves must care with us of things being their worth. So ahead with safety, and if they can't afford, let the thing on the table to see what happens.
RE: Trench cave in impact Foundation forms.
RE: Trench cave in impact Foundation forms.
I need to run some really quick calcs (because I feel this job is, at best, going nowhere) to give him a very preliminary design. Any ideas for a quick and dirty procedure to get the dynamic load? I was thinking F=MxA for a 1' width.
RE: Trench cave in impact Foundation forms.
The contractor now knows what needs to be done. He just doesn't want to do it.
There is no cheap, easy way to remedy this shoring problem. The contractor took a chance and lost. Now it's time to do the right thing. Anything less could cause additional problems. This is a contractor safety issue. As the engineer, you should stay out of it.
RE: Trench cave in impact Foundation forms.
Thanks for the input from both of you, and additionally I want to thank PEinc for all his contributions to this forum. It seems you are in every other post helping all of us out. I just hope one day I end up w/ half the knowledge as you.
Thanks!
RE: Trench cave in impact Foundation forms.