vibratory compaction equipment on under-ground structures. 1

[Prestressed Guy]

I have a client with a 95 year old house that sits on an unreinforced concrete basement. The city is doing a major road rebuild that will come within 25 feet of his basement wall. His concern is that the construction equipment will damage his home. The primary concern is about the vibratory compaction equipment.

 

[Qshake]

Haydenwse - I had a similar post though the equipment generating the vibration was more specific. Perhaps you can benefit from some of the answers. See the thread:

thread256-243406

A good reference is Soil Dynamics by Prakash where you will find a chart relating vibration to felt thresholds and structural damage amoung other things. The chapter is on Machine Foundations. It is not a clear answer but may be helpful.

You will find that much has been printed on particle velocity and it's relation to near and distant structures. So you can see how to mitigate damage by making sure the ground motion is below a certain threshold. It does not however help in the sense that if you have a certain vibration it will cause this much damage. The structural damage is, of course, dependent on the condition of the structure to begin with.

Invariably you will likely have to document the condition of the house and foundation in advance and following any work by the contractor. It will also involve some form of vibration measurement before and during construction.

good luck.

Regards,
Qshake

Eng-Tips Forums:Real Solutions for Real Problems Really Quick.

 

[Ron]

Monitor the vibrations with a good seismograph and set the trigger limits to no more than 1/4 of the Peak Particle Velocity limit for historical structures (0.08 to 0.12 inches per second, depending on the reference).

Set up at least 3 geophones...one at the foundation (usually set just off the foundation to prevent back reflection), one at the property line, and one halfway between those two. If you hit the trigger at the property line, stop the activity and make them use static compaction, not vibratory.

 

[msquared48]

You know, it's not just the extra lateral pressure on the wall and the possibility of vibration induced settlement. I would also be concerned with the loosening of electrical and plumbing connections with the likelihood increased of a long term fire and water leak damage.

He should have hius lawyer draft a letter and raise the idea of compensation for this increased risk as an addidional lever to have then employ the static compactor.

There is a precedent on this if there is documentation and associated problems with the items during or shortly after the compaction. Similar to being compensated for long term medical problems after an accident.

As mentioned above...document, document, document. Good luck.

Mike McCann
MMC Engineering

 

[Prestressed Guy]

Thanks for the responses.

Ron, in the thread provided by Qshake, you mention some Florida DOT guidelines for controlling construction vibrations when working near existing structure. That sounds like just the ticket for my needs. Were you able to locate them.

The project is in its public comment phase and the home owner wants to know if there are road construction techniques that would be less likely to cause problems. There is not a lot of fill required on this project which will help. From a “gut felling” level it would seem that high frequency and lower centrifugal force and amplitude would reduce the distance and impact of the equipment. Does that sound correct?

 

[Prestressed Guy]

One additional question.

This client has experienced ground water problems during the wet season (WA State) and is planning to install a French drain between the house and the roadway that will connect to a large catch basin that has been installed in the lower back yard. The native soil is mostly clay. I am curious if leaving this trench open throughout the construction would serve to isolate the structure from the construction vibration?

 

[Ron]

Haydenwise...yes, the trench will help, but you still need to monitor the vibrations....I have attached a document that will help you with the vibration limits. It is the CALTRANS criteria...I still can't find my FDOT document...will keep looking.

 

[Ron]

For some reason, it didn't upload...here it is..

 

[Prestressed Guy]

Thanks for paper Ron. That gives me a lot of information.

It appears that the types of equipment that will be used on this project are not typically associated with architectural or structural damage at the 20-25 foot minimum distance my client will have.

I went to the Blastmate web site and it appears that these units connect to a PC and run off software that is downloaded from the site. Is this correct and do you have any idea what these things cost?

 

[Ron]

We typically use Geosonics equipment because it is self contained. We rent the equipment and you can get various rates, depending on the time you intend to have the equipment.

I just reviewed a report in a litigation project where the opposing side used Blastmate equipment. Their results were very similar to ours under the same conditions of monitoring, thus seemingly good agreement between the pieces of equipment.