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Drilling in
Flowing
Sands

Overcoming a sandy situation

A major challenge for any driller is trying to drill with flowing sands. The term flowing sands refers to a mixture of fine sand and water that infiltrates drilling equipment. This problem often arises when using hollow stem augers to perform SPT tests. The flowing sands will enter the hollow stem auger and prevent a driller from obtaining an accurate sample.

Another common example is during the installation of stand pipes or piezometers. If you are trying to install a piezometer at a depth of 20 meters, you may have difficulty making connections at 10 meters.  Once you reach 20 meters, you may notice 3 meters of sand inside your augers.  Unfortunately, it is impossible to set a piezometer in place without removing the sand. 

As you advance an auger to 3 or 4 meters beyond the water table, fine sand particles try to make their way into the auger.  The deeper you go, the more difficult the situation can become.  The annulus of the borehole contains a large amount of water.  When the volume of water on the outside of the augers becomes greater than the volume of water on the inside of the auger, the pressures want to equalize.  This means that water from the outside of the auger wants to travel to the inside of the augers and there are only 2 ways it can get there.  It can either be forced in from the bottom or it can flow in from the auger joints.


Prevention can be the key

The solution is to prevent the flowing sands from entering the auger early. You can add water to your hollow stem auger every time you make a new connection which will help equalize the pressure.

You can also use dry auger connections which come with an O-ring on the pin and a compression seal in the box end. This will seal the augers and prevent material from entering through loose or worn connections.  There are other options available but why not contact a tech support technician for advice?

Learn more about
Fordia Hollow Stem Augers.

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