Do trench boxes qualify as "shoring"?
Do trench boxes qualify as "shoring"?
(OP)
Background: A 25' wide trench has to be constructed 14' deep in a 25' corridor. There is no room to lay back the slopes. There are buildings on shallow foundations adjacent to the trench.
If the design engineer has specified that the contractor use shoring for the construction of the trench---do trench boxes qualify as "shoring"?
If the design engineer has specified that the contractor use shoring for the construction of the trench---do trench boxes qualify as "shoring"?





RE: Do trench boxes qualify as "shoring"?
For the conditions you specify, I would say that a trench box would not be appropriate. The reason is the adjacent buildings on shallow foundations.
If you use a trench box, there is likely to be some ground loss adjacent to the box; which is likely to result in settement of the adjacent buildings.
Shoring/trench protection serves two purposes. 1. to protect the workers in the trench. 2. to protect adjacnet improvements. Number 1 is always required, number 2 is not always required.
RE: Do trench boxes qualify as "shoring"?
RE: Do trench boxes qualify as "shoring"?
I hope that the design engineer did more than just say "use temporary shoring". What foundation loads are on the adjacent buildings? In my opinion, a "designed" temporary shoring system incorporating soil conditions, adjacent building loads, groundwater, etc. would be required in this case.
RE: Do trench boxes qualify as "shoring"?
RE: Do trench boxes qualify as "shoring"?
Mickney, a trench box can be designed for all of the items you list. However, what the design does not consider are the points I just made to DRC1. The box may be strong enough to support the loads but the construction method is what can get you into trouble.
RE: Do trench boxes qualify as "shoring"?
RE: Do trench boxes qualify as "shoring"?
The existing structures need to be underpinned or the excavation properly supported to prevent lateral movement and coresponding settlement. Sheet piling, soldier piles and timber lagging or caisson wall depending on the soil conditions, groundwater, and type, condition and load on the adjacent foundations to be supported.
This is the kind of project that causes lawsuits when the neighbours building settles and cracks as a result of excavation. Don't fool around an get into trouble.
RE: Do trench boxes qualify as "shoring"?
RE: Do trench boxes qualify as "shoring"?
So, 2 contractors include full blown shoring in their price (h-piles and timber lagging or sheet piling). The third contractor indicated that he was going to use trench boxes. Contractors 1 and 2 bids were $3 million, contractor 3's bid was $2 million.
So, as the owner and/or the engineer what do you do? Do you throw out the 3rd bid as non-responsive? If the owner doesn't have the backbone to stand behind the engineer's requirements to use "shoring" and not trench boxes, what should the engineer do?
RE: Do trench boxes qualify as "shoring"?
RE: Do trench boxes qualify as "shoring"?
It is pretty clear from the responses above that trench boxes are personnel protection devices and not shoring walls.
So, as the engineer, do you demand the contractor to provide shoring in compliance with your bid documents for his bid amount of $2million?
If the owner will not back you, what do you do?
RE: Do trench boxes qualify as "shoring"?
You have adjacent buildings on shallow foundations. Therefore, you should underpin the buildings unless they are a sufficient distance away from the trench. If there is ground water above subgrade, proper dewatering will be needed to underpin the buildings.
RE: Do trench boxes qualify as "shoring"?
If the low bidder is presented with the issue before the contract is signed, he may withdraw his bid. If you were to accept the bid, THEN point out the problem, there might be some legal implications for you, and a small contractor could end up being driven into the ground before the project is done - can't get blood from a turnip - and everybody loses. Riggly above mentioned the issue of a 25-foot trench box being feasible. If you and the owners accept a proposal that you know is of doubtful feasibility, seems you are asking for huge claims, and maybe worse.
It's probably the owner's call, but you'll still need to cover your own butt in case the neighbor's footings are affected by the lack of shoring. If they aren't doing what you think is correct, send them a registered letter describing the risk and your recommendation not to proceed without real shoring. Don't know if that's complete protection for you, but it would help in getting their attention.
RE: Do trench boxes qualify as "shoring"?
RE: Do trench boxes qualify as "shoring"?
RE: Do trench boxes qualify as "shoring"?
It does depend on what the situation is. If it is a slab or pile foundation and you are a few feet away and there is no water, maybe it is not a big deal. If it is a significant structure and you are below the footing or the water table or both, then it is a big deal. I suspect since the other two biddres had more substantial systems it is a big deal. I would also talk to the other bidders to get their perspective.
However, I would not allow price adjustment. The other bidders will object. Either decides it meets spec and is what you want and award or rebid clearly stating what you want.
RE: Do trench boxes qualify as "shoring"?
It may be that all the "shoring" has to do is protect the people in the trench.
There are a lot of good opinions above, but they all guess about the information I have questioned about. DRC1 hit on it a bit with the fact it is situational.
RE: Do trench boxes qualify as "shoring"?
Many times engineers are placed in the role of being the lead individual on a project and you are charged with opening, verifying, and accepting the bids. In this instance, the engineer clearly called for shoring to be utilized. And yes, the engineer had his reasons for requiring shoring---type of soil, proximity of adjacent structures, etc. Bottom line is that the plans called for shoring. A bid was turned in that ignored the engineer's requirement and proposed to use trench boxes---which is not shoring and does not accomplish the intent of the engineer's requirement.
It's not up to you to re-evaluate your design and lower your requirements to fit the contractor's bid, it's not up to you to allow him to re-visit his bid and add money to included shoring, it's up to you to enforce the requirements on the drawings to keep the bid market fair and equitable. Had the contractor bid the shoring as specified and provided the owner with a deductive alternate to use trench boxes---fine. But as the bid was turned in, in my opinion, it should have been deemed non-responsive and thrown out.
RE: Do trench boxes qualify as "shoring"?
The point of the original question is wheather a trench box can be considered shoring. The consensus of posts, and my personal opinion, is that in some cases a trench box can be considered shoring and in some cases it can't.
RE: Do trench boxes qualify as "shoring"?
Seems like this is the owner's call, rather than the engineering consultant's. If permitted by the fine print in the bid documents (and considering potential litigation from the unsuccessful bidders), the owner may expect some big cost savings to be had from lower unit costs on other items of work. Obviously, the owner isn't going to pursue it for a dollar per yard on a few thousand yards, but if the money looks more substantial, it might make sense.
RE: Do trench boxes qualify as "shoring"?
RE: Do trench boxes qualify as "shoring"?
RE: Do trench boxes qualify as "shoring"?