Bore and jack - Required soil data 1

[geomatt01]

I have a project where bore-and-jack construction will be used to install a 48 inch sewer line through a 30 foot roadway embankment and I want to know what soil data is necessary beyond typical exploration bore logs?

Does anyone have a knowledge of what information a contractor will need? Are densities and gradations sufficient? Soils may be either dense granular or cohesive.

 

[rchanke]

Info extracted from borings with SPT should suffice. ie. densities, gradation, soil classification.

 

[DRC1]

1. A very good topo map
2. Lots of borings esp. at the jacking pit.
3. Look for evidence of obstructions.
3. SPT's and sievs are of for sands, but strength, and permiability should be done for cohesive soils
4 observation wells with good groundwater data should be obtained for granular or cohesive, but esp. cohesive.
5. Any evidence of contamination.
6 if you are using steel pipe, consider the effects of coal ash or stray electrical currents. Both are common around railroads, both can accelerate corrosion of the pipe.

Do most jacking jobs do this - No. Do many jacking jobs have extras that run many many more times what this program will cost? Yes. Its the owners call - he can pay you now or pay the pipe jacker later.

 

[rchanke]

With reference to DRC1's comments - I'd pay the pipe jacker later. If there are unforeseen conditions or obstructions then the contractor should be compensated, but they'll have to document this. Will a more robust exploratory program uncover this? Possibly, but then again it may not. Reasonable data should be provided. If reasonable data is not,,, then once bid documents are distributed the contractors may point this out and request additional info.

 

[DRC1]

Paying the pipejacker later will be significantly more expensive than paying the soil engineer now. It is true a more extensive investigation may not turn up all interference problems, but it will reduce the likelyhood of them. It is also true that the investigation won't make the obstructions go away, but knowing the obstructions a re there will a.) let you reconfigure the layout to reduce or miss the obstructionsor if not, b.) allow the extent of the obstructions to be quantified, and allow the pipe jacker to anticipate the work and price it competively as part of the bid. This will give you a better price than payig it as extra work later. Finally once the project is being bid, the pipe jackers will bid on the information provided, unless it is terible.In the few weeks there are to bid a project, a reasonable phase II testing program can't be done.
The better the information the bidders have, the better the bids.