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Are you well experienced in Excavation Support?
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Posted By Lee Mac
....., if so, I need your help.
We have a few excavations to begin soon, all around 3.5m deep.
The majority of them we can use trench boxes as support, however there are a number of these which contain utilities cables like spaghetti junction.
This is my quandary- we cannot slope or step off the sides due to space limitations and trench boxes are not a viable option due to the utilities.
If anyone can offer advice it would greatly appreciated.
Cheers,
Lee
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Posted By Steve B
Lee,
Firstly I would ask, who is doing the job for you? the reason I ask is that most utility companies that I have worked with tend to shore anything deeper than 1.2m and depending on the ground conditions may shore below that depth. further to this, if you are employing a competent civils company or utilities company, they will/should have street works qualified, competent ground workers who can identify hazards and defects in an excavation and therefore specify the type of shoring required. they will/should also have competent, qualified excavation inspectors who can also spot dangers and defects in excavations and specify any remedial actions.
My advice is quite simple (individuals are killed in both shallow and deep excavations each year) if you are intending to do the job yourself and are not competent to spot the dangers THEN DON'T.
Regards
Steve
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Posted By Ian G Hutchings
Lee
I agree with the previous post. If you look at HS(G)150 'Health and Safety in Construction', 'Groundworks' it also gives some pointers. This does need expertise to ensure that whatever measures are used they are robust and correct for the work.
Ian
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Posted By Kevin Kelly
having some (but limited) experience with trenches I would advise you to enlist the services of a chartered civil engineer to survey the ground conditions and to design a type of shoring that can be dropped in. I appreciate the physical constraints but with the correct materials, acrows and metal road plate etc, it would be possible to construct shoring that can be placed in around the obstructions.
But I repeat this should only be carried out on the advice and instruction of a competent engineer. I am just trying to point out that you are not limited to just trench boxes.
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Posted By Steve99Jones
In this type of instance you will need interlocking sheet piles, aluminium walings and hydraulic props. Much will depend on the actual ground conditions as they are exposed, ie: how much water is presence, is the material free flow, self supporting etc.
As a Chartered Civil Engineer, I can confirm that you cannot design these things in advance, yes you can make assessments, but what you really need is a competent foreman/supervisor on site who can make the decisions and ensure that the required supports and bracing is provided. The advantage of sheet piles is that they can be driven down as the excavation progresses, and left high (or substituted with a shorter pile) in any location where you encounter services.
The other thing you need to allow for is plenty of 'Time', these type of excavations cannot be rushed and treated like a normal trench.
I hope that this helps.
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Posted By Lee Mac
Thanks Lads,
No need to be concerned, everyone involved have the appropriate training and yrs of experience. I have checked their references and they are all excellent.
We are currently looking at the use of angled shoring with the use of props, then attaching the horizontal shoring with props to the upper layers.
But due to the high density of cabling and pipelines I was looking to see how others have performed in the past given the density of surrounding utilities.
Any past POSITIVE solutions will be well received.
Lee
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Posted By Ron Hunter
This may be a bit "off the wall", but would working from within a suspended enclosure make any sense?
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Posted By Jason Holmes
Have you spoken to the "Cable" & "Pipe" owners regarding their assets? You may need an Access certificate to work within a certain distance (i.e. medium pressure gas main) and would have to provide method statements etc (Cast Iron Gas mains in particular can be brittle and would also need supporting).
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