What measures to take under slabs where good compaction is unlikely
What measures to take under slabs where good compaction is unlikely
(OP)
Friends
I have a slab on grade carrying storage loads. Somewhere this slab is interrupted by a wall that goes down into earth to form a part of a channel.
Now at the junction between the slab and the wall there is a 90 deg bend and a fill there is not likely to be well compacted being next to a wall which will be cast in place before the slab is cast.
What additional measures must be made down there
Thanks IJR
I have a slab on grade carrying storage loads. Somewhere this slab is interrupted by a wall that goes down into earth to form a part of a channel.
Now at the junction between the slab and the wall there is a 90 deg bend and a fill there is not likely to be well compacted being next to a wall which will be cast in place before the slab is cast.
What additional measures must be made down there
Thanks IJR





RE: What measures to take under slabs where good compaction is unlikely
If you have already backfilled with granular material but are convinced it does not have sufficient bearing capacity, then consider pumping grout into the interstices to stiffen up the backfill. Be careful with this one not to pump at too high a pressure for fear of blowing the wall over.
If your slab supported by the wall then I think you have to provide sufficient rebar in the slab to span the distance from the wall to the good subgrade. If this is too far then you may have to consider small piles with a reinforced slab. Another solution if the fill area is too large is to use vibrated stone columns as a ground improvement technique which will incrase the bearing capacity of the fill.
Regards
Andy Machon
RE: What measures to take under slabs where good compaction is unlikely
IJR
RE: What measures to take under slabs where good compaction is unlikely
Operate in all time zones 24hrs a day!!!. My employer doesn't allow us poor engineers to sleep. Anyway, least I could do to after the sterling work you did on my connection problem.
Regards
Andy Machon
RE: What measures to take under slabs where good compaction is unlikely
RE: What measures to take under slabs where good compaction is unlikely
*THANKS KAM*
I am assuming the fill and slab are already in place. If you are not sure of the fill compaction, why not have a geotechnical consultant drill thru the slab in a few places and perform manual auger borings with penetrometer testing every 6 to 12 inches? While this would not tell you the exact unit weight of the fill, it would give you a relative idea of the soil stiffness. You could have a few additional borings done in areas of the slab where you know the fill was properly compacted to calibrate the penetrometer data to the suspect area.
If the soil was not compacted properly and is sandy, it can be chemically grouted to give it a cohesion component and turn it into a weak sandstone. Another option might be to remove the slab in this area, preload the soil with stacked product, and then re-pour the slab with adequate jointing. A specialty ground modification contractor, such as Hayward-Baker, could install compaction grout columns from the base of the slab to a firm soil layer to transfer slab loads through the weak zone. Grouting tends to be expensive.
RE: What measures to take under slabs where good compaction is unlikely