"Running Sands" in geotechnical borings
"Running Sands" in geotechnical borings
(OP)
Knowing that you will be explaining it to a structural engineer with limited knowledge of geotech - When I see "running sands" noted in a boring log: What are they, why do the slow down borings, and why can they be blamed for inaccurate blowcounts?
Thanks for any input, i've never heard of this phenomena and now have seen it pop up on two jobs in the past two weeks.
Thanks for any input, i've never heard of this phenomena and now have seen it pop up on two jobs in the past two weeks.





RE: "Running Sands" in geotechnical borings
The resultant is slurry like. The terminology is often cited by drillers. This sand/silt falls into the borehole when the hole is uncased and on removal and replacement of drilling tool the depth drilled previously is not reached and hence the hole has to be cleaned out.
This is often a battle as the sand keeps running into the hole as the tool is removed for cleaning.In many instances a hollow stem auger has to be used to case the hole through the zone of the running sand.
If the hole is not cleaned properly, yes the sloppy "running sand" material will form part of the thickness through which the SPT will be taken and hence low blow counts will be recorded. The geotechnical technologist would make a note of this problem and this is what you would have seen on the drill hole logs.
If the drilling contractor was not equipped with hollow stem augers, then that would be the end of the drilling.
If rotary drilling is used with drilling mud then this problem can be largely mitigated. Generally the drillers have the experience to apply bran to the mud etc, etc.and with a fluid inside this tends to prevent the running sand condition unless an artesian condition is encountered.
Hope this helps. Others may have input as well on this topic.
RE: "Running Sands" in geotechnical borings
RE: "Running Sands" in geotechnical borings
RE: "Running Sands" in geotechnical borings