|
Author:
David Green
|
1999-09-04 |
|
| |
|
|
| |
We plan to drive steel sheet piling in ballast subsoil within 10 ft of an occupied buiding. The owner is insisting we do not exceed a PPV of 2 mm/sec. Is this possible to achieve using a resonance free vibratory pile driver and is there research evidence available ?
Very grateful for advice - our project is on hold while we satisfy this demand.
David Green
London
England
|
|
| |
|
|
Follow-up:
| |
Author:
Mike Holloway
|
1999-09-20 |
|
| |
|
|
| |
The problem you pose may be very difficult to resolve with vibratory driving. A wall constructed from piles installed without vibrations (e.g. Tubex piles) might be a legitimate alternate.
The European vibratory driving devices with variable frequency and amplitude controls would have the best chance of controlling vibrations to such a low magnitude.
The 2 mm/sec PVS value is stringent, but does conform with measurements we have made, where settlements of pile-founded test structures occurred with 2.5 mm/s PVS measured at the ground surface. The soils logged as medium dense sands to the toes of the existing piles (about 10 m embedded).
The most severe vibratory driving vibrations come from start/stop effects in conventional driving applications. To minimize vibration levels: avoid lateral "slapping" of the sheets due to out-of-plumb alignment of the hammer-pile system (a surface wave problem); activate the hammer oscillations at the frequency that maximizes the penetration rate, while maintaining "zero amplitude" of motion, thereafter engaging movement of the sheet pile; and similarly disengage the motion of the sheets prior to reducing the frequency of the oscillators.
We often perform vibration monitoring programs with "test piles" well away from sensitive structures to "dial in" the most effective scheme for controlling adverse ground vibration effects. At this low level of tolerable ground vibration amplitudes, such a test program would, perhaps, help to satisfy the objectives of all involved. Ground subsidence and vectorial peak particle velocities versus distance should be monitored rigorously.
Good Luck
|
|
| |
|
|
Follow-up:
| |
Author:
David White
|
1999-10-01 |
|
| |
|
|
| |
As Mike mentions, installation using a method which does not use vibration could solve your problem. Standard steel sheet piles can be 'pressed' into the ground using a hydraulic piler. These machines are rare in the UK but common throughout Japan. Giken Seisakusho Ltd (who have an office in London) manufacture and operate the 'Silent Piler', which can press piles in with minimal noise, vibration and settlement. For a desciption and pictures of this machine, visit http://www2.eng.cam.ac.uk/~djw29/giken_frame.html.
|
|
| |
|
|
Follow-up:
| |
Author:
K. Rainer Massarsch
|
1999-12-18 |
|
| |
|
|
| |
Sorry that I did not see your question earlier - but you may still be interested to my response.
The first question is the reason for limiting the acceptable vibration level to 2 mm/s,is it a structural/settlement-related requirement or environmental (e.g. human concerns, sensitive equipment etc.).
If the problem is settlements, these will oncly occur in granular soils, but there (especially in loose, water-saturated sands or silts) this is a relevant level.
If the problem is environmental, you should check at what location and in what direction the maximum PPV is specified. If it is the most sensitive location (upper floor), there may be problems.
It is difficult to give a reassuring answer but I have been involved in several projects where such work has been carried out successfully.
You need to consider a number of aspects, such as sheet pile type and size, soil conditions and especially the upper layer (you may wish to pre-excavate the top 2 m, if this is a stiff or compact fill). If the subsoil is medium dense you may encounter the least problems.
Resonance during start-up and shut down of vibrator can create highest vibration levels. This can be avoided by using variable amplitude vibrators.
We have developed electronically monitored vibro-pile driving systems, using variable frequency and amplitude vibrators (see pile infor section of geoforum.com, search vibrators). A geophone is mounted at the cirtical location, then the monitoring system is programmed to vary the driving parameters such that the maximum PPV is not exceeded. You may contact me for more details, should you be interested.
|
|
| |
|
|
Follow-up:
| |
Author:
K. Rainer Massarsch
|
1999-12-18 |
|
| |
|
|
| |
Sorry that I did not see your question earlier - but you may still be interested to my response.
The first question is the reason for limiting the acceptable vibration level to 2 mm/s,is it a structural/settlement-related requirement or environmental (e.g. human concerns, sensitive equipment etc.).
If the problem is settlements, these will oncly occur in granular soils, but there (especially in loose, water-saturated sands or silts) this is a relevant level.
If the problem is environmental, you should check at what location and in what direction the maximum PPV is specified. If it is the most sensitive location (upper floor), there may be problems.
It is difficult to give a reassuring answer but I have been involved in several projects where such work has been carried out successfully.
You need to consider a number of aspects, such as sheet pile type and size, soil conditions and especially the upper layer (you may wish to pre-excavate the top 2 m, if this is a stiff or compact fill). If the subsoil is medium dense you may encounter the least problems.
Resonance during start-up and shut down of vibrator can create highest vibration levels. This can be avoided by using variable amplitude vibrators.
We have developed electronically monitored vibro-pile driving systems, using variable frequency and amplitude vibrators (see pile infor section of geoforum.com, search vibrators). A geophone is mounted at the cirtical location, then the monitoring system is programmed to vary the driving parameters such that the maximum PPV is not exceeded. You may contact me for more details, should you be interested.
|
|
| |
|
|
Follow-up:
| |
Author:
Jan Kenkhuis
|
2001-03-02 |
|
| |
|
|
| |
David,
It is not a problem at all to keep the PVV even below the 1 mm/sec. Especially light weight sheetpiles will drastically reduce the vibration generated.
It is the combination of a stiff sheetpile, not centric connected to a not balanced vibratory hammer which cause the problems.
In case we could be still of help let us know.
For Resonance Free vibratory hammers look at
http://www.ice-bv.nl
|
|
| |
|
|
Return
to subject 'Piling'
|
Follow-ups:
|
Subject:
steel sheet pile driving near residential building 