Compaction grouting 2

[pelelo]

Engineers,

I have a compaction grout project. The rule of thumb all the time has been to grout up to 10 ft below the surface.

My question is, isn't it possible to grout up to 5 feet below ground?.

I understand that there is a concern with ground heave. But still, i still think 5 ft below ground surface should be fine.

This is for an open field project. There is no structure, it is just a depression in a open field.

Of course, the idea is to first fill the depression and then proceed with grouting.

Please let me know your thoughts.

 

[oldestguy]

My experiences with one firm is generally this. They like to prepare the site so they have no "blow outs", by creating a barrier near the ground surface, such as in the 4-5 ft zone, some times shallower to "pump against".. Then they may work down, but usually run their inject pipes down say to 12-15 ft, zone depending on what needs fixing. gradually bringing it up injecting as they do. ..
When settled non uniformly, they adjust the injection amount and its location to tilt it back right and that may even take a little right up under the object. On rare occasion grout may go to off job places known as to where it went. One job had major quantities go to "who knows where" with no evidence as to where, possibly rock crevices.

 

[BenjaminR]

Hi pelelo, if I may add my two cents:

In my experience, compaction grouting is usually terminated ~10 feet below the surface because there is not enough overburden to allow the grout to compact the soil. Yes, you can get heaving, but the in situ soil is still below your target compaction level...once had a contractor who wanted to try compaction grouting to the surface to reduce his over-excavation; all we were left with was a lot of heave and some moderately hard blobs of grout among the still loose alluvial deposits.

And to oldestguy's anecdote, grout quantity should be included in the list of termination criteria...you can pump grout into a storm drain or sewer all day long.