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Author:
David Green
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1999-09-04 |
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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
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Follow-up:
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Author:
K. Rainer Massarsch
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1999-12-18 |
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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.
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Follow-ups:
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Subject:
steel sheet pile driving near residential building 