Hello, everyone.

This is Enta.

Do you know what this is?

 

Actually, this is a coupler lol

This is the coupler for the D51 rock bolt, lol.

Honestly, this size is just too funny.

By the way, this plated couplerAbout 10,000 yen each

 

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But that's beside the point.

I seem to recall writing about this topic on Ameblo before.

Maximum length of rebar for skid-type double-tube rock bolts.

But I actually get asked that quite a bit.

To the general contractor and the local government.

The reason I'm asking is because I have to remove the coupler.

Plated Coupler Design Prices/Reference

D19 Plated Coupler: 650 yen each

D22 Plated Coupler: 700 yen each

D25 Plated Coupler: 800 yen each

D29 Plated Coupler: 950 yen each

That amount will be gone, equal to the number of bolts multiplied by the unit price, lol.

Well, since the contract amount will go down, I’d wonder, “Why take it off?”

 

In my case, because there is a coupler,Mistakes are also likely to occurThat's what I think.

Actually...

The thread on rock bolts is kind of coarse, lol (though there’s no such thing as “coarse” threads, lol).

To explain what I mean, since the thread size is large,

Even the slightest vibration can cause it to come loose.

As anyone who has done this kind of work will know,

Even if you tighten it really tight with a pipe wrench, it still comes loose just from the casing vibrating lol

Have you ever had a situation where something came loose after you removed the casing?

 

Screws come in two types: standard-pitch and fine-pitch, and

The fine particles are difficult to dislodge, have high friction, and exert strong shear forces.

The threads on rock bolts are very coarse, so they come loose easily.

Even though the work was done properly, there is a possibility that it could end up coming loose.

Also, if a coupler is attached, it cannot be inspected during non-destructive testing.

The ultrasound is blocked by the coupler.

I really want them to do a thorough investigation, so no matchmaker for me, lol.

 

If the length is 6 meters or less, installation can be done without a coupler.

 

See you later.