Dexpan project, how to make the holes?

crazyal · Feb 27, 2018

When I built my house I ran into some ledge. I priced out doing it myself and then got two different quotes. One was high but the other was cheaper than anything I could do. It was large enough so the guy could justify bring in his drilling rig but after removing the blasted rock there was still a little left. When he came back he just used a small tow behind air compressor, something like an IR 185 and a hand drill to make the holes. I was here when he did the first blast, maybe 100 yards away and there was just a little bump in the ground and it was over. No blast noise, no dust, just a little rumbling feeling in the ground. If there were buildings close by then blasting mats would of been needed which would of added to the price.

I would call some rental places and see if they rent a drill. The air compressor should be easy. If you can get your tractor to the site then you can get the compressor. I have both an SDS and a larger spline drill with an 1 1/4" bit and once you get over 1" it's slow drilling.

Egon · Feb 27, 2018

Figure out a pattern for your drilled holes to get straight edges with fewer on the inside to save on drilling and dexpan.

You might also vary the timing of the dexpan so the exterior edges have a place to crack to.

bdog · Feb 27, 2018

I drill holes for explosives. It depends on the type of rock. Some rock we can drill with a special auger bit but other requires a down hole hammer. Our hammer is connected to a 210 cfm compressor. It works on a traditional drill string where the air is forced down the drill pipe and actuates the hammer. The hole is 3.5”. It can drill through virtually any type of rock but it is a loud dusty process. Our drill is mounted on a skid steer. I haven’t timed it but about a foot a minute in hard rock would be my guess.

Cord · Feb 27, 2018

Do you have any pictures of the SS mounted rig?

Cord · Feb 27, 2018

Egon said:
You might also vary the timing of the dexpan so the exterior edges have a place to crack to.

I was thinking about that as well. Drill and load the center holes and then start drilling the next row and then load those next. Keep on repeating as you work your way out.

crazyal · Feb 27, 2018

bdog said:
I drill holes for explosives. It depends on the type of rock. Some rock we can drill with a special auger bit but other requires a down hole hammer. Our hammer is connected to a 210 cfm compressor. It works on a traditional drill string where the air is forced down the drill pipe and actuates the hammer. The hole is 3.5”. It can drill through virtually any type of rock but it is a loud dusty process. Our drill is mounted on a skid steer. I haven’t timed it but about a foot a minute in hard rock would be my guess.

3 1/2" is a big hole. I can see that taking lots of time to drill into rock. I think the guy who came here used either a 1 1/2" or 1 3/4" bit. I do know the air compressor would blow the dust out of the hole as he drilled. I wasn't here for when he came back and did it with a hand held pneumatic drill. It took longer to reposition his rig than drill the holes. If I had to guess it was less and a minute per hole to go down 4'.

bdog · Feb 27, 2018

Cord said:
Do you have any pictures of the SS mounted rig?

It originally attached to the skid steer with the quick attach but was too front heavy. I actually flipped the skid steer over frontwards with about 30 lbs of dynamite on board. That was fun. We took the arms off the skid steer and mounted it solid.

bdog · Feb 27, 2018

crazyal said:
3 1/2" is a big hole. I can see that taking lots of time to drill into rock. I think the guy who came here used either a 1 1/2" or 1 3/4" bit. I do know the air compressor would blow the dust out of the hole as he drilled. I wasn't here for when he came back and did it with a hand held pneumatic drill. It took longer to reposition his rig than drill the holes. If I had to guess it was less and a minute per hole to go down 4'.

Yes but that is the smallest hole size we can use and be able to fit the explosives down the hole. They come in plastic tubes that are nearly 3" in diameter. The solid rock is slow but with moving around between holes we often can drill around 1,300' of hole a day in mixed conditions.