Figure 59. Ice failure site cleaned out and ready for patching.
is placed in the cavity and bonded to the existing
proximately 7.5 to 10 cm (3 to 4 in.). Any
material.
excess ice should be removed from the run-
way.
We had great success using the procedure out-
4. Slowly fill the hole containing the crushed
lined below. In all cases repaired areas stood up
ice with cold water (ideally very near 0C)
to the most rigorous proof rolling within 48 hours
to approximately 75% full. Fill the hole by
of patching. The supplies required include a long-
directing the water around the perimeter of
handle chisel, a welder's slag hammer or a rock
the hole (Fig. 60). Mix the ice-water slurry in
hammer, a coal shovel, and a source of cold fresh
the hole with the chisel or shovel by vigor-
water.
ous vertical probing to ensure that all pore
1. Empty any loose ice from the area to be
spaces are filled with water and to encour-
patched and place it to the side for later use.
age water to flow into any cracks radiating
Clean the faces of the cavity to allow clear
into the surrounding ice. After about an hour,
inspection of the ice along the sides and
proceed to add water to approximately 5 cm
bottom (Fig. 59).
(2 in.) below the ice surface. Smooth the
2. Using the chisel, excavate the area surround-
surface with the back side of a shovel. Allow
ing the failure area in order to make certain
it to cool for 34 hours. After this amount of
that all of the weak ice has been dislodged.
time the surface usually will have frozen
If a large area of the surrounding ice is weak,
over (Fig. 61).
use one of the large-scale test methods to
5. Using the chisel, break the top of the ice
break up the weak ice and identify its areal
surface in a number of places (10% of total
limits.
surface area). Slowly reflood the patch area
3. The ice that was removed from the failed
to fill the air gap under the ice surface with
area should be further broken up with a
cold water.
hammer into pieces roughly the size of a
6. Use a bright-colored flag (e.g., orange) to
person's fist or less. The crushed ice should
mark the location of the patch on the ice
be packed into the cavity to fill the hole
surface. A corner of the flag can be frozen
into the surface using cold water. If the run-
slightly above the level with its top by ap-
58
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