Bolts, spits, plugs and feathers

It was time for another cave rescue training. And this time, our Training Officer wanted us to practice gently breaking a rock. You can have a situation when a rock falls on someone, and it is impossible to just lift it off; it might have to come down in bits. The quickest way of doing that is blowing it up, but that is dangerous if there is someone nearby. So that is why the gentle methods would come in. We would have a go with plug and feathers.

When we were gathered on the parking lot from which we would walk up to Wrysgan, he told us he had a few more tricks up his sleeve. We also do some placing of anchors. We had expansion bolts and spits. And he had a bolt testing rig with him. These are for checking the safety of an anchor; they have to withstand 5 kN for 15 seconds without showing any fluctuations.

I had been used to expansion bolts in the Southwest. I had never used a spit! They are quite old-fashioned. They only go in about an inch, and the actual plate you attach to them is fixed only with a thread that is not much more than a centimetre long, so they are not as robust as actual bolts. But you can hammer them in by hand. Before battery drills, that was what everybody used. Nowadays I don't think many people use them anymore, but it is thinkable that you sometimes might be in a situation where you can't use an electric drill. And then they are a lot better than nothing!

We walked up. Normally, you walk past a pond on your way up. But in this dry weather, that pond was just not there! You could see that mountain bikers or motorcyclists had already used the pond bottom as a playground. 

No pond! 

Beautiful views

At the entrance we put on a lot more clothes as inside, it would be quite cool. We went in, and I first had a go with the spit. Our training officer wanted that on a nice big flat rock, so once it would be in, he could use that testing rig, and people could stand around. The rock he pointed out looked very hard. It wouldn't be where I would put a spit for anything other than demonstration purposes! But if he wants it in there, he can get it in there. I started hammering away.

Minutes later I didn't have a hole for a spit, but I did have a spit without teeth. If he wanted it in there, he wasn't going to get it after all! That convinced him that indeed, that rock was not a good choice. I went to a nearby piece of slate and started again. With a new speed. Fortunately, they are not expensive. And it was cool to see how well it actually works! But by the time I had hammered it down about halfway I was keen to swap with someone else. And a big strong bloke named Gareth took over.

I had a bit of a look at what else was happening. Sharon (yes, there was another woman!) had placed an expansion bolt, and we were now going to test it. It did fine on the 5 kN test. But the testing rig can go a lot further! We cranked it up to 10. Still fine. You could carefully hang a small car from that! I think we managed to get it over 20 kN, but towards the end you could see small fluctuations. Yes, we are not likely to ever put a force like that on an anchor. Shock loading a rope is something that routinely happens in climbing, of course; in underground exploration, much less so. And although shock loading, in an unfortunate situation, can get you to 5 kN; it is not likely to get you anywhere near 20 kN. 

Bolt testing rig

Some people were also being quite successful with the plug and feathers we had. You have to hammer them in, and if a rock is lying on top of you I can't imagine it being a pleasant sensation if people started hammering it; but sometimes, the end justifies the means.

We then also tested the spit. This came with an aluminium plate. When we put some serious force on it, that plate just bent out of shape. The actual spit was not budging at all until it was really really loaded heavily! I was quite impressed. I would happily trust my life to something like that. It's just not very likely I ever will.

Video made by Ed

When we had done all that, we packed up again and went back down. And there the midges had taken over, so we didn't linger particularly long.

Quite soon we will already have our AGM. That is, in the greater scheme of things, a much more important gathering. But this had been quite enjoyable!