Coring through low strength materials

[jrl802]

Hello,
I’m trying to get some general feedback on the benefits or problems with coring through low strength material in order to validate permeability requirements are within specifications. The material is testing at about ~200 psi 28 day right now.

I have heard both good and bad things from other colleagues but yet many big seepage remediation jobs (dams, levees, etc..) require some type of verification coring.

Thanks!

 

[BigH]

Can you please explain better your material - you say low strength - 200 psi (which is about 1.4 MPa or 14.4 tsf) - but you don't say what kind of material it is . . . is it rock? low strength concrete? or very hard clayey soil?

You also do not say what kind of coring you want to do. Is this surface coring (say using a concrete coring machine)? Or is it deeper cores where you would use a diamond drill / diamond bits?

Any material can be cored (negating stiff to very soft clays / cohesionless) if (1) you have the right drilling equipment for the job, (2) the right set-up (to minimize vibration) with the correct rods, etc. and (3) and most importantly on critical work the right (very best) driller.

Explain a bit more details . . . just also remember that it is heavily frowned on to drill through a dam's core (auger rig and sonic rig excluded - but not really liked).

 

[jrl802]

It is a mix of soil (sands and silts), cement and bentonite. Also known as self-hardening slurry. The coring is for verification of permeability specifications.

It is surface coring utilizing some kind of wire line or conventional technique. I’m not clear on the specifics of the coring system yet because the contractor has not submitted it to us yet. The concern is with damaging the intended seepage barrier.

This is not a dam core.