Civil Engineering Reference
In-Depth Information
(a)
(b)
2
2
3
Floor plan
4
1
3
1
Path of inspection
Floor plan
5
Door
4
6
Enter
Enter
(c)
Ceiling
Upper
left
quarter
Upper
right
quarter
Figure 11.22
Method of
making building damage
surveys: (a) wall
identification procedure;
(b) multi-wall identification
procedure; (c) detailed wall
identification procedure
(Office of Surface Mining,
2001).
Lower
left
quarter
Lower
right
quarter
Floor
thorough (Figure 11.22). In addition to the build-
ing survey, a public relations program informing
people of the blasting operations, and carefully
documented vibration measurements will usu-
ally minimize complaints and spurious damage
claims.
recommended stemming and burden dimensions.
Therefore, in areas where there is a possibility
of damage to structures, blasting mats should be
used to control flyrock. Blasting mats consist of
rubber tires or strips of conveyor belting chained
together. When there is a possibility that the mat
could be displaced by the explosive energy, they
should be weighted with soil, or anchored to the
bedrock.
11.5.2 Control of flyrock
When the front row burden is inadequate or when
the stemming column is too short to contain the
explosive gases, a crater is formed and rock ejec-
ted from the crater may be thrown a considerable
distance (Figure 11.23). This figure also shows
that flyrock can be caused by poor drill alignment,
and by geologic conditions that allow venting of
the explosive gases along discontinuities in the
rock mass.
In practice, the complete control of flyrock is
difficult, even if the blast is designed with the
11.5.3 Control of air blast and noise
These two problems are taken together because
they both arise from the same cause. Air blast,
which occurs close to the blast itself, can cause
structural damage such as the breaking of win-
dows. Noise, into which the air blast degenerates
with distance from the blast, can cause discom-
fort and give rise to complaints from those living
close to the blasting operations.
