Vibrations from Pile Driving on Adjacent Trunk Sewer

[EireChch]

Hi all,

I am involved in a project where we are going to construct a multi-storey carpark development that is to incorperate a retail portion. Plan area of approximately 50m x 60m, 5 storey high.

The site is a closed landfill with subsurface ground conditions comprising very soft landfill material (silts andclays, with varying quantities of fine gravels, glass, metal pieces, steel wire,wood/timber, and plastic.) to 6.5m depth. Strength testing within this layer indicated SPT N values (3 to 5) recorded, generally indicated the
presence of low strength (firm) soils. Shear strengths measured at the end of open barrel tube coring were of firm to very stiff (35kPa to 102kPa) consistency, typically
between 35kPa to 41kPa (firm).

Below this, natural alluvial soils (alternating bands of silt and clay with occasional fine gravels) were encountered to 25m depth. Strenght testing indicated SPT N values of 3 to 11 were generally measured to a depth of approximately 25m. Below 25m depth, highly weathered siltstone and sandstone was encoutnered. Beyond this depth, the SPT N values increased to 34 to 50 plus, indicative of dense to very dense soils.

Due to the presence of existing landfill materials and soft/firm alluvial soils, we consider that the proposed structure will need to be supported on piled foundations. In this instance, driven steel H piles should are considered suitable. As an envirionemtnal requirement, the piles will be pre-drilled to 7.5m depth and concrete encased to prevent lechate leaking into natural ground. Pile driving will commence at 7.5m depth.

An existing trunk sewer rising main (525mm steel lined concrete pipe) is located adjacent to the footprint. THe invert of the pipe is 3.5m deep i.e. the pipe is supported on landfill material. We understand that the pipe is in relatively poor condition, as you would imagine.

As the closest pile is 2.5m away, the governemnt body looking after Wastewater reticulation has asked us to comment on the potential effects of pile driving vibrations on the pipe. We envisage vibrations to be relatively minor as minimal initial driving force will be required to reach the bearing stratum (i.e. 25m depth).
Pile driving will commence at 7.5m depth below the existing ground surface, which is approximately 3.8m depth below the trunk sewer invert level.

I am keen to get other engineers opinions on this and have engineers come across similar situations. I have googled on line but found nothing of any real use. Any help or references would be very helpfull.

Thank you.

 

[Ron]

Without regard to what you think might be damaging to the pipe, in my opinion you should monitor the vibrations during construction to determine their frequency and magnitude. This is for your protection.

In the US, there have been numerous studies on the effects of vibrations on existing structures, including damaged structures or structures that have less than robust structural systems such as older, historical buildings.

Check the following references:

Construction Vibrations by Charles Dowding
Vibrations of Soils and Foundations by Richart, Hall and Woods (an older text, but relevant)
Vibration info from CalTrans (California Department of Transportation). They have quite a bit of info on this and some might refer to infrastructure effects.

 

[BigHarvey]

Have a look at "Ground borne vibrations from piling" by PJ Whyley and RW Sarsby, Ground Engineering, May 92, pp32-37. It gives a prediction of the ppv as a function of distance, hammer energy and soil resistance.

 

[EireChch]

Thanks for the replies bigharvey and Ron. I have google search the books and can't find a link to get a free copy. I am reluctant to buy them! Would anyone have a link to a free copy?

Thanks

 

[Ron]

EireChch....here are some public domain docs to help....

 

[Ron]

Here's another

 

[Ron]

and another....

 

[EireChch]

Thanks Ron that's very helpful

 

[SlideRuleEra]

EireChch - In addition to recommendations from Ron and BigHarvey, here are some points that you can present to the governing body to minimize their concern:

1. You are using H-pile. Vibration from driving displacement (e.g. concrete) piling is more of a problem.

2. You are predrilling to a significant depth before driving begins.

3. If you select a lower energy hammer transmitted vibration should be reduced. Of course the hammer still has to be adequate for the job.

4. Drive piling that are near the pipeline first, then move away from it in a planned orderly schedule.

These recommendations are taken from this Florida DOT document, page 15, but my own experience as a bridge contractor who drove our own piling confirm them:

http://www.dot.state.fl.us/statemat...e/grip/2013/12a_svinkin-vibrationlimits-2.pdf

http://www.SlideRuleEra.net

http://www.VacuumTubeEra.net