Determining Quantites for Sand Backfill
Determining Quantites for Sand Backfill
(OP)
I am wondering what the best way to calculate backfill quantites for a trench, clay site with utilities under a road, I would assume that the side slopes would have to meet some standard and that also a box may affect the situation at some depth. I'm looking for a cubic yardage per lineal foot based on any particular depth.





RE: Determining Quantites for Sand Backfill
RE: Determining Quantites for Sand Backfill
RE: Determining Quantites for Sand Backfill
RE: Determining Quantites for Sand Backfill
Yes, there are standards that have to be met. Where is the site?
Please see FAQ731-376 for great suggestions on how to make the best use of Eng-Tips Fora.
RE: Determining Quantites for Sand Backfill
RE: Determining Quantites for Sand Backfill
Please see FAQ731-376 for great suggestions on how to make the best use of Eng-Tips Fora.
RE: Determining Quantites for Sand Backfill
RE: Determining Quantites for Sand Backfill
Lay out your trench and then assume a sideslope like above and for incremental depths, say 1', calculate the volume per linear foot. Use average end area to calculate volumes or assume a constant ground elevation and approximate the volume.
RE: Determining Quantites for Sand Backfill
Please see FAQ731-376 for great suggestions on how to make the best use of Eng-Tips Fora.
RE: Determining Quantites for Sand Backfill
RE: Determining Quantites for Sand Backfill
http://www.osha.gov/SLTC/trenchingexcavation/
While you may think the guidelines are excessive (many engineers do) I can assure you that your company is setting itself up for big trouble if you flout them. I have seen many excavation collapses (not in trenches.) They are sudden and very unpredictable - and trench collapse is still the single greatest cause of construction site deaths.
Please play it safe - and smart.
Please see FAQ731-376 for great suggestions on how to make the best use of Eng-Tips Fora.
RE: Determining Quantites for Sand Backfill
I ask, because it appears as though you may be a wee bit inexperienced for this task. The average area method will work well, but you will have to consider the compacted density of your backfill verses the hauled density. I am assuming of course that you are importing the sand. The number you are looking for, unfortunately, does not exist.
For open cut, your quantity of sand backfill increases almost exponentially with depth due to the requisite sidewall excavations. If you are using a cage, it is a little easier, but your productivity slows dramatically and there will be some questions of compaction due to the movement of the cage.
If it is possible, I would utilize the sand for bedding and the pipe zone and then utilize the native material for backfill. For road crossings, perhaps you may wish to consider unshrinkable fill (fillcrete) for backfill.
KRS Services
www.krs-services.com
RE: Determining Quantites for Sand Backfill
RE: Determining Quantites for Sand Backfill
RE: Determining Quantites for Sand Backfill
KRS Services
www.krs-services.com
RE: Determining Quantites for Sand Backfill
Zambo
RE: Determining Quantites for Sand Backfill
To reply ro Zambo, I am most concerned with development projects where a new road is constructed.
RE: Determining Quantites for Sand Backfill
If the trenches are backfilled with sand, how does the municipality later remediate the failures due to settlement or differential heaving?
We used to use sand as an exclusive backfill, but found it to be deterimental to the road structures after several freeze/thaw cycles. As of the last 15 years or so and depending on the soils and moisture contents (relative to groundwater tables) we have developed specs which utilize the native soils as backfill. This has proven to save not only initial project costs, but also long term maintenance. It is the value of the future maintenance costs where I have done many evaluations and had to revise existing standards as a municipal manager for several jurisdictions.
KRS Services
www.krs-services.com
RE: Determining Quantites for Sand Backfill
I always have a fight with the regulatory people regarding backfill. They like to use sand because it's written in a book somewhere.
Native backfill if compacted to natural density will almost always act the same way as the native material in the first place. Sand or gravel backfill will either drain the local material or be a path for excess moisture to enter the material. Frost lenses are a real possibility.
I had a client who operated an airfield. He had excavated a trench and backfilled it with granular material (native material was a silty clay.) The trench heaved in winter and subsidized in the summer. This caused him to close a runway for one winter until the material could be removed and backfilled with native material.
To get in situ densities, simply use your density gauge while excavating. Take several measurements and have the same densities with the backfilled material.
Rick Kitson MBA P.Eng
Construction Project Management
From conception to completion
www.kitsonengineering.com