Using a sonotube (a cardboard tube) to prevent drag down during a surcharge period
Using a sonotube (a cardboard tube) to prevent drag down during a surcharge period
(OP)
Hi
I have a project to construct an embankment fill in between two retaining walls. The foundation type of these walls is driven steel pipe piles.
The soil is expected to have a long term settlement due to embankment fill (the soil at the site is soft to medium stiff clay). I recommended to have a surcharge (over the embankment fill) and a settlement period before driving piles. The contractor suggests the procedure given below.
1. Excavate to bottom of footing
2. Drill 30” hole 5’ deep and place 30” x 5’ Sonotube (it is a cardboard tube)
3. Drive the piles to tip elevation
4. Fill the annular ring between the pipe pile and Sonotube with either pea gravel or sand
5. Fill any gap between the Sonotube and dirt with slurry
6. Place dirt for surcharge
The idea of the Sonotube is that it will prevent drag down during the surcharge period.
Does anybody know about such a procedure?
(I do not know why contractor suggests the depth of the hole to be only 5’. I think it should be more than that, extending to cover the compressible soil layer).
Thank you.
I have a project to construct an embankment fill in between two retaining walls. The foundation type of these walls is driven steel pipe piles.
The soil is expected to have a long term settlement due to embankment fill (the soil at the site is soft to medium stiff clay). I recommended to have a surcharge (over the embankment fill) and a settlement period before driving piles. The contractor suggests the procedure given below.
1. Excavate to bottom of footing
2. Drill 30” hole 5’ deep and place 30” x 5’ Sonotube (it is a cardboard tube)
3. Drive the piles to tip elevation
4. Fill the annular ring between the pipe pile and Sonotube with either pea gravel or sand
5. Fill any gap between the Sonotube and dirt with slurry
6. Place dirt for surcharge
The idea of the Sonotube is that it will prevent drag down during the surcharge period.
Does anybody know about such a procedure?
(I do not know why contractor suggests the depth of the hole to be only 5’. I think it should be more than that, extending to cover the compressible soil layer).
Thank you.





RE: Using a sonotube (a cardboard tube) to prevent drag down during a surcharge period
Assuming a good end bearing for piles, theoe downward loadings usually can be tolerated, such as for bridge backfill at abutments, as a road over a stream.
RE: Using a sonotube (a cardboard tube) to prevent drag down during a surcharge period
www.PeirceEngineering.com
RE: Using a sonotube (a cardboard tube) to prevent drag down during a surcharge period
www.SlideRuleEra.net
www.VacuumTubeEra.net
RE: Using a sonotube (a cardboard tube) to prevent drag down during a surcharge period
www.PeirceEngineering.com
RE: Using a sonotube (a cardboard tube) to prevent drag down during a surcharge period
Negative skin friction is almost always present (long term), and only requires 1mm to 2mm of relative movement between the adjacent soil and pile to engage. So don't de-rate your pile geotechnical capacity because of negative skin friction without understanding the settlement behavior, or you will end up de-rating every pile.
A good reference for this topic is B. Fellenius, who discusses negative skin friction and drag load and downdrag at great length in several papers and are core ideas in the Unified (Pile) Design Method.
RE: Using a sonotube (a cardboard tube) to prevent drag down during a surcharge period