Tips for Core Recovery

Geotechnical drilling comes into play when you’re working with oil rigs or when you evaluate a site prior to construction.  After the geotechnical survey is completed, you’ll have a profile of the soil throughout the site.  The lets the engineer team plan out the foundation and columns knowing that they will be supported by the ground once they have been placed.

One of the most important steps in geotechnical drilling is core retrieval.  The core is a sample of soil from a specific depth and at a specific location on the site.  It’s important to retrieve the core precisely and to come back with plenty of material for testing. 

The issue is that it can be difficult to extract a good core sample.  You may be dealing with clay or shale, or soil that is too sandy or rocky.  Each different type of soil presents its own challenges, some more so than others.  However, there are a few tricks you can use to make it easier to extract a pristine core, saving time and effort while providing a higher level of quality.

Cores are extracted through a process called diamond drilling.  Once you drill to the desired depth, you drive a tube into the ground at that depth, forcing material into the mouth of the tube and filing it to create a core.  Here’s what you can work with:  The smoother the inside of the tube, the easier it is for the core to enter the tube.  Anything you can do to smooth out the inside of your tubes will give you higher quality and make life a good bit easier when you’re extracting the core.

Tip #1: Chrome-Plated Inner Tubes

Chrome plating is a great way to get a smooth surface on the inside of your tubes.  Since the smooth, hard finish helps the core to enter the tube more easily, these tubes are ideal for broken ground and times when it’s challenging to extract the core.  Another benefit of chrome-plated tubes is that they are resistant to rust.  The humid and high sulfide conditions underground leave most tubes rusty and pitted, making it more challenging to extract a core.  However, chrome-plated tubes will not rust so long as the chrome is intact.

So you might ask, if chrome-plated tubes are so great, why don’t we use them all the time?  And, if you’ve ever tried to buy them, you know exactly why.  These tubes are quite expensive, so you might not realise how much they’ll save you over time.  Try one out for your challenging extractions, and you’ll see right away.

Tip #2: Linseed soap

If you’re not ready to spring for the chrome-plated tubes just yet, no worries.  One trick often used by experienced drilling contractors is to use linseed soap on the inner surface of the tube before you use it.  This trick has been around for as long as drilling has, and there’s a reason for it.  Linseed soap is relatively cheap and easy to use.  It comes in tubs, and you just take a handful and press it into the mouth of the tube.  The soap is forced through the inner tube as it descends the rods string and enters the water table.

These are just a couple of tips that will make your drilling job easier and offer a higher quality of core.  If you’d like to know more about drilling tips or tricks, or if you have a job you’d like to discuss, feel free to contact us.  At BG Drilling, we’ve got you covered.

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