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1 day shoring to meet OSHA.

1 day shoring to meet OSHA.

1 day shoring to meet OSHA.

(OP)
I have a situation where we need to dig a 15' Deep trench for a 10' dia. x 60' long water tank.  The trench only needs to be open for about 1 day.  OSHA requires us to shore the trench or layer it back. Is there an easy and cost effective solution  shoring the trench.  The solution can bend, but it cannot break.  Assume 1. We cannot layer back the slopes, 2. We have no room to tieback the top.  Any suggestions?  Thank you.

RE: 1 day shoring to meet OSHA.

To rent the services of someone that has the required number of jacking modules, maybe?

RE: 1 day shoring to meet OSHA.

Can you vibrate in some sheet piles for the day and pull them once the trench is backfilled?

RE: 1 day shoring to meet OSHA.

(OP)
It often seems like bracing a trench can cost more time and money than what you are putting in the trench.  I do not need a rigid structure, like alot of the long term solutions show.  The structure can bend, but it cannot break or overturn. 1) The trouble with jacks, is they get in the way of inserting the tank.  2) The trouble with having someone drive in sheet piling is that it is going to cost $40,000.   

RE: 1 day shoring to meet OSHA.

A 15' deep trench is approximately twice the height of the room you are sitting in.  Do it right. Install sheeting.  Slope a couple of feet off the top and install some cantilevered sheeting.

www.PeirceEngineering.com

RE: 1 day shoring to meet OSHA.

There is no mention of soil type or water/seepage. Usually, the bottom 4' can be essentially vertical, if and only if, the top portion thereafter is properly sloped or benched (and if soil is suitable/stable). Advice from geotech is required. No short-cuts I hate to say. Why can you not slope: property line issues? You have to think about men going down there as well (I presume, to level the bottom or compact the base?) Do not take a risk!

RE: 1 day shoring to meet OSHA.

The excavator has steel shoring box for trench excavation. It shall suffice, check with earth work contractor.

RE: 1 day shoring to meet OSHA.

I serously doubt you could install the 60 feet long tank with steel shoring boxes in place. Same thing with struts. tie backs, sheet piling, or a laid back trench would work. Soil stabilzation using grouting might work. I can think of no temporary methods that are cheap.

RE: 1 day shoring to meet OSHA.

A 20' diameter water main was constructed in DuPage County, Illinois, in the 90's. It stretches a few miles long, and in the dead center of streets. It was done using the steel shoring boxes so there was ample driving space left besides the excavation. The general contractor was KENNY, I believe.

RE: 1 day shoring to meet OSHA.

cntw1953 - pipe comes in short segments, jointed together. for large pipe these joints are usually only 8 - 10 feet long. therefor the pipe joints can be inserted between the struts on the boxes which are slightly longer. However, this is a 60 feet long tank and I assume it does not come in segments, just one piece (WDS1 - correct me if this an incorrect assumption). if so you would need 60 feet of clear space (without struts) to drop the tank in. how will you shore this 60 feet long section?

RE: 1 day shoring to meet OSHA.

They may have to provide construction joints.

RE: 1 day shoring to meet OSHA.

If your area has a hard freeze condition, you may want to leave the excavation opened for a few days until the soil is frozen hard and that should be in compliance with OSHA.

RE: 1 day shoring to meet OSHA.

are you kidding? frozen soil is in compliance with OSHA? good luck trying to pass that one by the OSHA inspector.

RE: 1 day shoring to meet OSHA.

CVG, isn't that what was done on one of the sites at the Big Dig in Boston? after all if the soil is stabilized several inches deep on trench walls and flooring from being frozen hard, what is the problem?

RE: 1 day shoring to meet OSHA.

first of all the soil would have to be suitable, ie: dry sandy soil - would not work. Wet clay soil, maybe? Second - several inches deep would not provide global stability and the trench wall could still collapse. Third, it is not quick or cheap. I believe sheetpiles would be cheaper.

The process is described below and doesn't sound cheap or fast.

"Pipes would first be installed using directional drilling at an angle ... Then, super-chilled salt water would be continuously pumped and recycled back through the pipes to freeze a four-foot thick layer of the soil beneath and on the sides of the pits..."

RE: 1 day shoring to meet OSHA.

Weather/temp alone may not do the trick, but some deep freezing methods might do.

RE: 1 day shoring to meet OSHA.

Commercial soil freezing would most likely be extremely expensive for the original situation described by wds1.  This is a very small shoring project.  Again, if possible, slope a couple of feet off the top and install some cantilevered sheeting that is about 12' high.

www.PeirceEngineering.com

RE: 1 day shoring to meet OSHA.

Yes, freezing, using engineering design, can work.  You need someone that knows how to do it and is willing to put their career on the line to sign off on a system that will keep people alive.  

Leaving something open to the air to freeze a bit of it is ridiculous, and never an approved method that I have seen.

RE: 1 day shoring to meet OSHA.

Ground Freezing involves pumping chilled prine through a network of wells. It is highly spealized and generally the most expensive option. OSHA lists some trenching details. Anything (including all steel sheet piling) that does not comply with these details must be stamped by a PE. Shoring boxes need to be certified by a PE (usually included in sales documents) and must be on site. Boxes have limitations on depths of excavation. The biggest boxes I have seen are 30 feet cclear. Those are very heavy and require a couple large backhoes or a good size crane to handle. If you have a stiff clay, you may have some options. If you have sand, I agree with PEInc that your best bet is sheeting or soldier pile and lagging. I would suggest you have a local geotech look at the site. In my opinion, $40,000 seems like a really good price ($20 per sq foot) Note that a leading cause of construction fatalities is trench and shoring collapse and it was generally in an excavation that would be open for a few hours or so.  

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