Hello, everyone.

This is Enta.

The other day, I tested with an employee to see if I could carry a 133 double-pipe casing all by myself!

Of course, this is how it turned out for me...

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But that's beside the point.

Measures to Prevent Sand Blowing Caused by Groundwater Pressure, a Common Issue with Temporary Anchors

The job site I was working on last week was a real struggle~ lol

 

Drill hole diameter: φ135

Total Length: 15 m

Machine: Crawler-type percussion (RPD3A-130C3A)

Soil type: Gravel and sand

 

We will proceed with the installation as usual.

It suddenly starts jamming by about 2 to 3 meters once it goes past roughly 7 meters.

Drilling fluid does come up. (A little.)

With an anchor this size, the machine has plenty of power to spare, so it should be fine, but it’s been tightened so tight it’s squeaking.

Once you go past this layer, it becomes a layer of pure sand.

The cause is this river gravel, which I wrote about the other day.

This thing gets stuck between the outer and inner layers because it gets all bunched up in there. (It’s too big to come out of the swivel.)

I've gotten a pretty good sense of when they'll show up, so as long as I make sure to clean the inside of the casing regularly, there shouldn't be any problems.

 

The next layer is a sand layer, and because the internal pressure is high, the sand is pouring right up into the inner casing.

Even for that brief moment when connecting the double-tube setup, if you let your guard down for a second, it’ll get sucked into the inner tube and cause a clog. (River gravel also clogs the inner bit’s discharge port.)

There were only 13 this time, but I had to retrieve about three of them because the sand wouldn't come out of the inner liners lol.

 

We have completed the 15-meter borehole.

Insert the measuring rod. (Super Yellow: Past Articles）

So even after subtracting the remaining length, the drilling length is only about 13 meters! lol

We're cleaning the inside of the hole! And we're doing a really thorough job, too.

Despite that, sand is being blown up into the casing.

When it comes to this, it's really tough.

Reinsert the liner and re-excavate.

I'm a little worried, so I'll dig a bit deeper. (I'll leave a generous margin.)

Insert the measuring rod.

As it turns out, the sand has indeed been blown up to a height of about 1 meter.

Sand layers really are a pain.

 

After trying all sorts of things, we ended up thinking, "Is this method the best we can do?" lol

I'll explain how to do that tomorrow.

 

See you later.