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| BRISTAR'S effectiveness, therefore, depends on
the placement of the holes. The drilling must be done in relation
to the job to be performed. |
Test
design and breaking
| The design for breaking should be
done according to the properties of rocks, joint, volume
to be removed, secondary breaking, and work period, etc.
Table 1 should be taken into account for the design.
Before experimenting with a test break,
reference should be made to 'Hole Design for Rock' or
'Hole Design for Concrete' links (on the left) to assist
in your special needs for successfully planning a break
design.
To determine which combination of hole
size and spacing is most desirable, drill several holes
of different diameter at different burden and spacing,
check each of the break conditions and then decide hole
diameter, depth, burden and spacing.
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Table
1. Type of Breaking by BRISTAR
| Type |
Secondary
breaking |
Fragmentation
Crack formation
Presplitting |
Hammer,
Power shovel
Hand breaker, Power shovel, Hydraulic breaker
Combination of mechanical breaker or dynamite |
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Drilling
| I. Drilling machine: Use electrical
drill, rock drill or crawler drill.
II. Drilling direction: It is preferable
to drill holes vertically, but in case of a wall
or pillar of reinforced concrete where vertical
drilling is hard, an inclined hole may be drilled.
Since a greater effect is achieved with a deeper
hole, in case of a thin material, consideration
should be given so as to get a long hole depth
by drilling it obliquely if necessary. Horizontal
holes can be applied to the same idea of spacing
as with vertical holes. III. Hole
Diameter and hole spacing: The breaking plan
of Table 2 can serve as a guidance in making a
decision. In general, the preferable hole diameter
is from 40 to 50 mm (1 1/2" x 2").
Table
2. Material and proper hole spacing
IV. Hole depth: This varies
with the shape of the material to be cracked or
the break plan. It should be noted that BRISTAR
mixed with water can easily be applied by hand,
when the hole depth is up to approximately 10
meters. When the depth is less than 3 times the
diameter of the hole, less cracking will occur,
the breaking effect is lessened and the time required
for demolition is increased.
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Use
of thin steel pipe
| In the case of a temporary
concrete structure (to be demolished), place thin steel
pipes (the thickness: 0.8 mm (1/32") i.e. a sheath
pipe for P.S. concrete as holes before placing concrete
instead of drilling. Whenever the structure needs to be
cracked , fill BRISTAR in the pipes. There is no change
in breaking effect by the use of pipe. |
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