mirror of
https://expo.survex.com/repositories/expoweb/.git/
synced 2024-11-26 01:01:58 +00:00
126 lines
6.7 KiB
HTML
126 lines
6.7 KiB
HTML
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.0//EN">
|
|
<html lang="en">
|
|
<head>
|
|
<title>CUCC Expo Handbook: rigging - artificial belays - bolts</title>
|
|
</head>
|
|
<body>
|
|
<center><h2>Bolt belays - placing and using</h2></center>
|
|
|
|
<p>Most people on Austria expeditions will be familiar with the use of bolt
|
|
belays from trips in the UK. In Austria, caves already explored will have
|
|
bolts with the hangers removed, which can be quite hard to spot. Anyone
|
|
hoping for a join-the-dots trip will be disappointed. These bolts can usually
|
|
be found fairly easily by anyone familiar with expo rigging, <i>provided a
|
|
good rigging guide was drawn up by the previous explorers</i>. Y-hangs are
|
|
common at pitch heads, so check that you find both bolts. Lower down, it is
|
|
as well to know whether a bolt has been placed for a rebelay or a deviation,
|
|
as it may not become obvious which until some way down the pitch. Such a
|
|
rigging guide is also useful to show which existing bolts should <b>not</b>
|
|
be used. Inevitably some bolts will be badly placed, or may become damaged.
|
|
It is as important not to use these as it is to find the right ones.
|
|
|
|
<p>For new pitches when, as is often the case, good natural belays are
|
|
scarce, you must place one or more bolts yourself. Doing so puts you in
|
|
a position of responsibility both for the safety of future users of that
|
|
bolt and for the conservation of the cave. The aim should always be to
|
|
put in good bolts which will contribute to a safe rig with a minimum of
|
|
further bolting needed.
|
|
|
|
<p>This is easier said than done, and there is ample evidence of this in
|
|
caves CUCC have explored over the years. The best place for a bolt may
|
|
be far from obvious until the pitch has been descended. Or maybe the best
|
|
place is obvious, but that place is hard to reach. It is tempting to try
|
|
to reach for the best placement, but overstretching or an insecure perch
|
|
may lead to a poor bolt in the perfect place. This is very much to be
|
|
avoided, since it is now impossible to put a good bolt in the perfect
|
|
place - the rock around the first placement will have been stressed and
|
|
another bolt should not be placed closer than about 20 cm from it.
|
|
|
|
<h3>Placing bolts</h3>
|
|
|
|
<p>Placing a bolt is a simple matter of drilling a hole and inserting a rock
|
|
anchor. The bottom end of the rock anchor is expanded by some mechanism,
|
|
and thus grips tightly in the hole, resisting any attempt to pull it
|
|
out. The anchor is strongest if loaded at right angles to its axis, ie.
|
|
parallel with the rock surface. Hence for a vertical pitch, it is normally
|
|
best to place the anchor in a vertical rock surface.
|
|
|
|
<p>The hole may be made in either of two ways. For the penalty of carrying
|
|
considerable extra weight, a cordless power drill is the quickest way to
|
|
drill the hole. The heaviest item is the drill battery, which must, of
|
|
course, be removed from the cave each time it needs charging. This method is
|
|
of the most use where a lot of bolts need to be placed on a pitch series
|
|
relatively accessible from an entrance. Lots of bolts are also needed for
|
|
climbs up or exposed traverses to reach inaccessible passages.
|
|
|
|
<p><center><a href="../../smkridge/161/l/boltin.htm"><img alt="(36k image)"
|
|
src="../../smkridge/161/t/boltin.jpg" width=113 height=152></a>
|
|
<a href="../l/bosch.htm"><img alt="(73k image)"
|
|
src="../t/bosch.jpg" width=200 height=200></a><br>
|
|
<b>Bolting by Hand Using the Drill</b></center>
|
|
|
|
<p>The older (and more reliable, but slower) method is to use the anchor
|
|
itself as the drill bit, driven in by use of a hammer. 8mm self-drilling
|
|
rock anchors have teeth around their bottom for this purpose. The anchor is
|
|
attached to a bolt driver, which is then repeatedly pounded with a hammer,
|
|
whilst rotating the anchor by hand every couple of whacks. When this gets
|
|
a little stiff, the anchor is pulled out of its hole and the dust and rock
|
|
chips blown out. The process is repeated until the top of the anchor is
|
|
just below the rock surface. A small conical "wedge" is then inserted into
|
|
end of the anchor (thin end into the anchor) and the pair put back in the
|
|
hole. Three or four good hard whacks with the hammer "set" the anchor by
|
|
driving the wedge into the bottom end, expanding it. Beware of hitting it too
|
|
many times, as this will start to weaken the rock around the anchor.
|
|
|
|
<p>The hole produced by the power drill is a different shape from that
|
|
produced by hand - since the power drill bit has a pointed end. It is also quite difficult to get the depth of the hole exactly right. For this
|
|
reason, if a self-drilling anchor is set into a powerdrill hole, the wedge
|
|
will not be driven into the anchor and an unsafe placement will result.
|
|
To use a self-drilling anchor, it is best to under-drill the hole, and
|
|
finish off to just the right depth, and a square hole-bottom with a hand
|
|
driver.
|
|
|
|
<p>More efficiently for power-drilled holes, use a form of anchor specially
|
|
intended for these holes. These anchors use a smaller hole, so you get more
|
|
holes for your money from one battery charge, and the design of anchor means
|
|
that the bottom of the hole is not used in the setting process, and the depth
|
|
of the hole is therefore less critical (as long as it is deep enough that the
|
|
anchor goes right in !)
|
|
|
|
<p><center><a href="../../years/1990/hilti1-300.png"><img
|
|
alt="before setting - 1k png" width=530 height=90 hspace=10 vspace=10
|
|
src="../../years/1990/hilti1-100.png"></a><br>
|
|
<b>Hilti HDK spits before and after setting.</b><br>
|
|
<a href="../../years/1990/hilti2-300.png"><img alt="after setting - 1k png"
|
|
width=220 height=94 hspace=10 vspace=10
|
|
src="../../years/1990/hilti2-100.png"></a></center>
|
|
|
|
<hr>
|
|
|
|
<!-- LINKS -->
|
|
<img alt=">" src="../../../icons/lists/0.png">
|
|
<a href="../index.htm">Expedition Handbook</a> - Intro<br>
|
|
<img alt="--->" src="../../../icons/lists/1.png">
|
|
Back to <a href="index.htm">Rigging Guide</a><br>
|
|
<img alt="--->" src="../../../icons/lists/1.png">
|
|
<a href="../look4.htm">Prospecting guide</a><br>
|
|
<img alt="--->" src="../../../icons/lists/1.png">
|
|
<a href="../survey/index.htm">Surveying guide</a><br>
|
|
<img alt="--->" src="../../../icons/lists/1.png">
|
|
<a href="../rescue.htm">Rescue guide</a><br>
|
|
<img alt="--->" src="../../../icons/lists/1.png">
|
|
<a href="../photo.htm">Photography guide</a><br>
|
|
<img alt=">" src="../../../icons/lists/0.png">
|
|
<a href="../../infodx.htm">Index to info/topics pages</a><br>
|
|
<img alt=">" src="../../../icons/lists/0.png">
|
|
<a href="../../indxal.htm">Full Index to area 1623</a><br>
|
|
<img alt="--->" src="../../../icons/lists/1.png">
|
|
<a href="../../areas.htm">Area/subarea descriptions</a><br>
|
|
<img alt="--->" src="../../../icons/lists/1.png">
|
|
<a href="../../index.htm">Back to Expedition Intro page</a><br>
|
|
<img alt=">" src="../../../icons/lists/0.png">
|
|
<a href="../../../index.htm">Back to CUCC Home page</a><br>
|
|
|
|
</body>
|
|
</html>
|