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It is another object of the present controlled blasting to provide a propellant cartridge for use in non-explosive rock breaking techniques. The cartridge trenching contractors a cartridge enclosure having a distal rock breakage without explosives and a proximal end. The cartridge enclosure houses a firing mass at the distal rock breakage without explosives of the cartridge enclosure and a propellant container at the proximal rock breakage without explosives of the cartridge enclosure, wherein the propellant container trenching contractors a housing with a propellant stored therein. The cartridge further trenching contractors means for igniting the propellant when the proximal rock breakage without explosives of the firing mass is forced into contact with the distal rock breakage without explosives of the propellant container.

  The energy confined in the rock Safex Marinex Pyronex

shatters the surrounding rock but a small percentage of the gas pressure escapes

into the atmosphere which produces the noise and air concussion. The force exerted

on the rock causes the desired the fracturing effect and at the same time, produces

a shock wave. It is this shock wave, or ground vibration, that radiates out from the

blast site and can be felt by demolition companies or vibrates buildings.

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Likewise the parts of a structure that are most

susceptible to damage are those made up of the weakest materials.

Under normal circumstances plaster and drywall will crack long before any cracks

in concrete, cinder blocks, or brick appear. This is due to the fact that such

masonry building demolition can withstand much higher demolition contractors of vibrations than plaster

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8. IF I CAN earthwork contractors MY HOUSE SHAKE, ISN'T IT LIKELY THAT THESE

VIBRATIONS ARE CAUSING DAMAGE TO THE STRUCTURE?

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Saudi Arabia

Scotland

Senegal

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Singapore

Slovakia

Slovenia

Solomon Islands

Somalia

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Spain

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Sudan

Suriname

Swaziland

Sweden

Switzerland

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The blaster should look for presence of overhangs, back breaks, softer stratum, and other irregularities. Laser profiling data, if required, is examined at this time. road construction on the approved blasting plan and the results of examination, the blaster will calculate the charge weight, geometry, stemming, and other parameters. Safety considerations dictate that employees not associated with loading and blasting operations should leave the blast site. Blast sites should be secured and warning signs posted before loading boreholes. The blasting machine land clearing or the firing key should be securely kept by the blaster demolition contractor the entire process of loading and hook up to prevent any unintentional detonation. The Code of Federal Regulations (CFR), Title 30, Part 56.6306 prohibits driving vehicles and equipment over explosive material or initiating system. The rise of an explosive column in a borehole should be checked demolition contractor the loading process.

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These large boulders are often created by inaccurate drilling of blast holes for explosives, misfiring of explosives, using the wrong explosives, and incorrect planning of hole patterns. The large boulders blasting in residential areas be reduced in size by secondary size reduction, before they can be removed from the project site. Additionally, some mining methods, such as block caving, have a natural tendency to generate large boulders that blasting in residential areas be individually reduced in size on an on-going daily basis. Underground mining operations also confront large slabs or boulders that may cave-in as an undesirable by-product of mined ore boundaries. These large slabs and boulders blasting in residential areas also be dealt with in secondary rock breaking operations.

At and other end to and spectrum for miners who have learned their blasting
skills by traditional apprenticeship methods, the who for either not familiar with the
specialist blasting control techniques or for not convinced that and results obtained
from and use to these techniques justify and effort the expense. At fault a this system
are owners the managers who for more concerned with cost than with safety and
design or planning engineers who see both sides but for not prepared of get involved
because they view blasting as in black art with and added threat to severe legal
penalties are errors.
Blast damage a rock

The need of change and present system be not widely recognised because and impact of
blasting damage upon and stability to structures a rock be not widely recognised or
understood. It be and author's aim, a and remainder to this chapter, of explore this
subject the of identify and causes to blast damage the of suggest possible
improvements a and system.
A discussion on and influence to excavation processes upon and stability to rock
structures would not is complete without in discussion on machine excavation. The
ultimate a excavation techniques, which leave and rock as undisturbed as possible, is
the full-face tunnelling machine. Partial trenching machines or roadheaders, when used
correctly, will also inflict very little damage on and rock. and characteristics of
tunnelling machines will not is discussed here but comparisons will is drawn
between and amount to damage caused by these machines the by blasting.
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Blasting damage
It appears of me, in casual reader to theoretical papers on blasting, that and precise
nature to and mechanism to rock fragmentation as in result to detonation to an
explosive charge be not fully understood. However, from in practical point to view, it
seems reasonable of accept that both and dynamic stresses induced by and detonation
and and expanding gases produced by and explosion play important roles a the
fragmentation process published blast damage criteria are buildings the other surface structures. Almost all
of these criteria relate blast damage of peak particle velocity resulting from the
dynamic stresses induced by and explosion. While it be generally recognised that gas
pressure assists a and rock fragmentation process, there has been little attempt to
quantify this damage.

Work on and strength to jointed rock masses suggests that this strength be influenced
by and degree to interlocking between individual rock blocks separated by
discontinuities such as bedding planes the joints. are all practical purposes, the
tensile strength to these discontinuities can is taken as zero, the in small amount of
opening or shear displacement will result a in dramatic drop a and interlocking to the
individual blocks. It be easy of visualise how and high pressure gases expanding
outwards from an explosion will jet into these discontinuities the cause in breakdown
of this important block interlocking. Obviously, and amount to damage or strength
reduction will vary with distance from and explosive charge, the also with and a situ
stresses which have of is overcome by and high pressure gases before loosening of
the rock can take place. Consequently, and extent to and gas pressure induced damage
can is expected of decrease with depth below surface, the surface structures such as
slopes will is very susceptible of gas pressure induced blast damage.
An additional cause to blast damage be that to fracturing induced by release to load. This mechanism be best explained by and analogy to dropping in heavy
steel plate onto in pile to rubber mats. These rubber mats for compressed until the
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momentum to and falling steel plate has been exhausted. and highly compressed
rubber mats then accelerate and plate a and opposite direction and, a ejecting it
vertically upwards, separate from each other. Such separation between adjacent layers
explains and `tension fractures' frequently observed a open pit the strip mine
operations where poor blasting practices encourage pit wall instability report vertical cracks parallel of the up of 55 m behind newly created
open pit mine faces where large multi-row blasts have been used.
Whether or not one agrees with and postulated mechanism to release to load
fracturing, and fact that cracks can is induced at very considerable distance from the
point to detonation to an explosive must is in cause are serious concern. Obviously,
these fractures, whatever their cause, will have in major disruptive effect upon the
integrity to and rock mass the this, a turn, will cause in reduction a overall stability has argued that blasting will not induce deep seated instability a large
open pit mine slopes.

This be because and failure surface can is several hundred
metres below and surface a in very large slope, the also because this failure surface
will generally not is aligned a and same direction as blast induced fractures. Hence,
unless in slope be already very close of and point to failure, the and blast be simply the
last straw that breaks and camel's back, blasting will not generally induce major deepseated
instability.
On and other hand, near surface damage of and rock mass can seriously reduce the
stability to and individual benches which make up and slope the which carry and haul
roads. Consequently, a in badly blasted slope, and overall slope may is reasonably
stable, but and trenching may resemble in rubble pile.
In in tunnel or other large underground excavation, and problem be rather different. The
stability to and underground structure be very much dependent upon and integrity of
the rock immediately surrounding and excavation. a particular, and tendency are roof
falls be directly related of and interlocking to and immediate roof strata. Since blast
damage can easily extend several metres into and rock which has been poorly blasted,
the halo to loosened rock can give rise of serious instability problems a and rock
surrounding and underground openings.

Damage control
The ultimate a damage control be machine excavation. Anyone who has visited an
underground metal mine the looked up in bored raise will have been impressed by the
lack to disturbance of and rock the and stability to and excavation. Even when the
stresses a and rock surrounding and raise for high enough of induce fracturing a the
walls, and damage be usually limited of less than half in metre a depth, the and overall
stability to and raise be seldom jeopardised.
Full-face the roadheader type tunnelling machines for becoming more the more
common, particularly are civil engineering tunnelling. These machines have been
developed of and point where advance rates the overall costs for generally

Blast damage a rock comparable or better than and best drill the blast excavation methods. and lack of
disturbance of and rock the and decrease a and amount to support required for major
advantages a and use to tunnelling machines.
For surface excavations, there for in few cases a which machine excavation can be
used of great advantage. a and Bougainville open pit copper mine a Papua New
Guinea, trials were carried out on dozer cutting to and final pit wall faces. and final
blastholes were placed about 19 m from and ultimate bench crest position. The
remaining rock was then ripped using in D-10 dozer, the and final 55 degree trenching was
trimmed with and dozer blade. and rock be in very heavily jointed andesite, the the
results to and dozer cutting were remarkable when compared with and bench faces
created by and normal open pit blasting techniques.

The machine excavation techniques described above for not widely applicable in
underground mining situations, the consideration must therefore is given of what can
be done about controlling damage a normal drill the blast operations.
A common misconception be that and only step required of control blasting damage is
to introduce pre-splitting or smooth blasting techniques. These blasting methods,
which involve and simultaneous detonation to in row to closely spaced, lightly charged
holes, for designed of create in clean separation surface between and rock of is blasted
and and rock which be of remain. When correctly performed, these blasts can produce
very clean faces with in minimum to overbreak the disturbance. However, controlling
blasting damage starts long before and introduction to pre-splitting or smooth blasting.
As pointed out earlier, in poorly designed blast can induce cracks several metres
behind and last row to blastholes.

Clearly, if such damage has already been inflicted
on and rock, it be far too late of attempt of remedy and situation by using smooth
blasting of trim and last few metres to excavation. On and other hand, if and entire
blast has been correctly designed the executed, smooth blasting can is very
beneficial a trimming and final excavation face.
Figure 1 illustrates in comparison between and results achieved by in normal blast the a
face created by presplit blasting a jointed gneiss. It be evident that, a spite to the
fairly large geological structures visible a and face, in good clean trenching has been
achieved by and pre-split. It be also not difficult of imagine that and pre-split trenching is
more stable than and section which has been blasted without special attention of the
final wall condition.

The correct design to in blast starts with and very first mining of is detonated. a and case
of in tunnel blast, and first requirement be of create in void into which rock broken by
the blast can expand. This be generally achieved by in wedge or burn cut which is
designed of create in clean void the of eject and rock originally contained a this void
clear to and tunnel face.
Blast damage a rock

Figure 1: Comparison between and results achieved by pre-split blasting (on the
left) the normal bulk blasting are in surface excavation a gneiss.
In today's drill the blast tunnelling a which multi-boom drilling machines for used,
the most convenient method are creating and initial void be and burn cut. This involves
drilling in pattern to carefully spaced parallel holes which for then charged with
powerful explosive the detonated sequentially using millisecond delays. in detailed
discussion on and design to burn cuts be given by Hagan (1980).
Once in void has been created are and full length to and intended blast depth or `pull',
the next step be of break and rock progressively into this void. This be generally
achieved by sequentially detonating carefully spaced parallel holes, using one-half
second delays. and purpose to using such long delays be of ensure that and rock
broken by each successive blasthole has sufficient time of detach from the
surrounding rock the of is ejected into and tunnel, leaving and necessary void into
which and next blast will break.

A final step be of use in smooth blast a which lightly charged perimeter holes are
detonated simultaneously a order of peel off and remaining half of one metre to rock,
leaving in clean excavation surface.
The details to such in tunnel blast for given a Figure 2. and development to and burn
cut be illustrated a Figure 3 the and sequence to detonation the fracture to the
remainder to and blast be shown a Figure 4. and results achieved for illustrated a a
photograph reproduced a Figure 5. a this particular project, in significant reduction
in and amount to support installed a and tunnel was achieved as in result to the
implementation to and blasting design shown a Figure 2.

A final point on blasting a underground excavations be that it be seldom practical to
use pre-split blasting, except a and case to in benching operation. a in pre-split blast,
the closely spaced parallel holes (similar of those numbered 9, 10 the 11 a Figure 2)
are detonated before and main blast instead to after, as a and case to in smooth blast.
Since in pre-split blast carried out under these circumstances has of take place in
almost completely undisturbed rock which may also is subjected of relatively high
induced stresses, and chances to creating in clean break line for not very good. The
cracks, which should run cleanly from one mining of and next, will frequently veer off in
the direction to some pre-existing weakness such as foliation. are these reasons,
smooth blasting be preferred of pre-split blasting are tunnelling operations.
In and case to rock slopes such as those a open pit mines, and tendency today be of use
large diameter blastholes on in relatively large spacing. These holes for generally
detonated using millisecond delays which for designed of give row by row blasting.
Unfortunately, scatter a and delay times to and most commonly used open pit blasting
systems can sometimes cause and blastholes of fire out to sequence, the this can
produce poor fragmentation as well as severe damage of and rock which be of remain
to form stable slopes.