Mysterious Boring Log Description

[AnotherDirtGuy]

Hi all,

I have a set of boring logs from a site in Quebec (so in French), which have a soil description I have never seen. In multiple logs a stratum is simply labeled "destructif" with no SPT results or additional notes. The hatching shown looks like clean gravel or cobbles but I am hesitant to make that assumption outright. Has anyone seen this before? These are old logs from a different job in the vicinity of my current project, so I'm trying to sort this out without contacting the original investigators if possible. Thanks!

 

[Mad Mike]

I strongly suspect it refers to "no recovery"...that is, no material was recovered for whatever reason and they've noted it as such. The "Recuperation" column agrees with this.

An odd way of doing things- usually the geologist infers what is represented by the missing material- they seem to have taken the no-liability approach and just recorded the missing core as thin air. Oh well.

All the best,
Mike

 

[BigHarvey]

"Destructif" means they used a destructive drilling method and were not able to put a description in front !
The problem is that they don't describe the destructive method they used and they didn't record drilling parameters therefore it doesn't give any information at all ! Was it necessary to drill...?

 

[AnotherDirtGuy]

Thank you, both. I agree with BH--what's the point of continuing to drill if you provide no additional information? Changing the hatching and giving no description raises more questions than it answers haha. Oh well is right.

My thought was it is weathered rock or some sort of rocky fill, based on the hatching and lack of recovery. Also, this is a flat urban location near to a river, so it's possible the site was formerly wetland that was reclaimed for development by filling with rock. Too bad they couldn't provide more details in these logs since we are installing utilities at this depth. We'll have to do some test pits.

 

[Mad Mike]

AnotherDirtGuy,

From my experience, complete core/material loss is almost invariably in clean sands, and less often in thoroughly decomposed sandy bedrock;- if it were a rocky fill being cored, all of the sand would usually be washed out but the stumps of rock core would be recovered and presumably noted on the logs.

My instruction to the driller in these difficult-to-recover-materials would always be to sample at regular intervals with a split-spoon (SPT test)- in rare cases the zero recovery is not the driller's fault at all.

As you say, dig some pits- my money is on you finding wet alluvial sand.

All the best,
Mike

 

[killswitchengage]

Yea i work with French all the time , destructif means just what it means and i suspect they made the decision to switch from sampling to destructif method