Geocito
Civil/Environmental
- Dec 14, 2007
- 9
thread274-42972
Hi everybody.
I'm involved with a project containing MSE mixed abutments on piles going through the MSE wall, and once read this thread and some documents by FHWA, I understand there are two construction options: either drive piles prior to face construction or use hollow sleeves at proposed pile locations during reinforced fill erection. The latter method is generally preferred. Predrilling for pile installation through the reinforced soil structure between reinforcements can also be performed but is risky and may damage reinforcing elements (source DCT 143).
In my case, the piles must be driven in advance and a sleeve (but for thin membranes) cannot be placed around them because it interferes with MSE reinforcement strands (they cannot be skewed anymore and already pass close to the piles edge). I'm prescribing means for negative skin friction reduction during MSE construction, but in the mentioned thread there appears a question I'm concerned about: unsymmetrical lateral loads applied to the piles during MSE compaction. Even if FHWA and AASHTO specifications about pile-wall distance are followed, the soil between them cannot be as well compacted as the soil behind the piles and because of the functioning of MSE walls (compacted soil kind of spreads in order to push the wall and the pressure is tied back by the reinforcement) I'm afraid lateral earth pressures from behind the piles are higher, rather than symmetrical, but I've not been able to find a method to calculate this pressure (if I'm right and it actually occurs) so as to be considered in the design of the piles. Make sense?
Perhaps my fears are unfounded, because I’ve seen documents and pictures where the earth is compacted against the piles (just skin friction reduction membranes are present), but I would like to find references to support this. Any idea?
Thanks
Hi everybody.
I'm involved with a project containing MSE mixed abutments on piles going through the MSE wall, and once read this thread and some documents by FHWA, I understand there are two construction options: either drive piles prior to face construction or use hollow sleeves at proposed pile locations during reinforced fill erection. The latter method is generally preferred. Predrilling for pile installation through the reinforced soil structure between reinforcements can also be performed but is risky and may damage reinforcing elements (source DCT 143).
In my case, the piles must be driven in advance and a sleeve (but for thin membranes) cannot be placed around them because it interferes with MSE reinforcement strands (they cannot be skewed anymore and already pass close to the piles edge). I'm prescribing means for negative skin friction reduction during MSE construction, but in the mentioned thread there appears a question I'm concerned about: unsymmetrical lateral loads applied to the piles during MSE compaction. Even if FHWA and AASHTO specifications about pile-wall distance are followed, the soil between them cannot be as well compacted as the soil behind the piles and because of the functioning of MSE walls (compacted soil kind of spreads in order to push the wall and the pressure is tied back by the reinforcement) I'm afraid lateral earth pressures from behind the piles are higher, rather than symmetrical, but I've not been able to find a method to calculate this pressure (if I'm right and it actually occurs) so as to be considered in the design of the piles. Make sense?
Perhaps my fears are unfounded, because I’ve seen documents and pictures where the earth is compacted against the piles (just skin friction reduction membranes are present), but I would like to find references to support this. Any idea?
Thanks