Subsurface Investigation 1

[Dubliner]

Dear all

I am seeking information on the availability and cost of either seismic or ground penetrating radar surveys, to be conducted on land in the Republic of Ireland.

Maximum depth of resolution required would be around 10-15m.
Borehole data from the site exists for 'truthing' the survey results.

If anyone can give advice or suggest a more appropriate forum for this question I would be most grateful.

Yours

Dubliner

 

[georam]

Could you contact local companies which deals with geophysical work there ? They can help you getting quotation for cost to do GPR or Seismic survey.

Of course there are many companies that can do the work internationally, if the job is big.

Companies like Geophysique GPR International work worldwide.

 

[coneboy]

Hello Dublin

If the ground/soil conditions permit you could do an electronic cone test with the seismic option. The seismic CPT test, called SCPT would give you a full log of the subsurface soils (grnd water pressures, lithology, density, soil strength and equiv SPT values etc)as well as shear wave velocities. If the CPT operator has good equipment then "P" wave arrival times can also be calculated.
On most sites you should be able to get 3 to 4 SCPT tests to a 15 m depth in a single day for $2000 - $3000.

If the ground conditions are rocky/lots of gravel or cobbles then you would need to do a down hole seismic test. This down hole procedure requires more time and a larger budget. I would estimate that downhole testing would cost $4000 for a single test location.

Check with local CPT operators and see who has the necessary equipment and who has experience in doing seismic testing. My experience indicates that geophysical companies will not come out to a site for smaller jobs such as this.....well, they will come out and work for you but the costs are really high (+$10 000)

A third method of getting seismic data would be to use a contractor with SASW equipment. SASW = Spectral Analysis of Surface Waves which is basically examining the rayleigh waves. I have used this method before and it works nicely, especially where you have horizontal continuity within the subsuface soils. It also helps if you have some kind of idea of the subsurface conditions as some forward modeling is required in order to produce S and P wave velocities from the rayleigh waves. A full day of SASW testing would cost approx $2 500 to $3 500.

We have tried GPR in the past and the results have not always been very good (A.K.A. we don't use GPR for shear wave velocity tests unless there is absolutely nothing else available).

Are you doing seismic testing for A)liquefaction purposes? B)machine foundation design? C) Subgrade modulus determination for a raft slab foundation?

I would check the "Fugro" web site as they offer many, if not all of these services in Europe.

Best of luck
Coneboy