Building Materials, Third Edition

‚™2—2ƒ TQ

4. The number of charges fired, the number of charges exploded and the misfires should be
   recorded.


5. Explosives should be stored and handled carefully.


6. Detonators and explosives should not be kept together.


7. Cartridges should be handled with rubber or polythene gloves.


8. A maximum of 10 bore holes are exploded at a time and that also successively and not
   simultaneously.

i
 …  —X The composition and characteristics of the various blasting-
powders and their suitability are given in Table 3.4.

ƒ—  i
X The explosives should be stored in a magazine (a special type of
building) which should be away from residential areas, petrol depots, etc. The magazine
should have ventilators at high levels and should have concealed wiring. It should be protected
from lightning. Smoke or fire should not be allowed in the nearby area. Explosives should be
protected from extreme heat or cold and also from moisture. They should be handled carefully
and gently. The magazine should be surrounded by barbed wire and the entry should be
restricted.

—  i
 ‚X The quantity of explosive required depends upon several
factors such as strength of explosive; method of blasting; number of bore holes—their size,
position, etc. and the type and mass of rock to be dislodged. It is very difficult to incorporate
all the factors in an expression and obtain the exact amount of explosive required. A rough
estimate can be made by:

A =

L^2

0.008

where A = quantity of gunpowder or dynamite (g)

L = length of line of least resistance (m)

QS xe„…‚ev2fih2yp2ƒ„yxi

It is the original bed, plane or position occupied by a stone during its formation in a sedimentary
rock. The stones should be so placed that the load line is at right angles to the natural bed. In
the case of metamorphic rocks, the plane of foliation or the plane of cleavage is assumed to be
its natural bed. It is very difficult to trace the natural bed in the case of igneous rocks and the
natural bed is not given due attention. The right placement of stones with regard to the load
line is shown in Fig. 3.7 for a few cases.

QT ƒieƒyxsxq2yp2ƒ„yxi

A freshly cut stone carries some natural moisture known as quarry sap making it soft and
workable. The quarry sap is a mineral solution and reacts chemically with the mineral
constituents when the stone is exposed to atmosphere after quarrying. The stone becomes
harder and compact. The process takes about 6 to 12 months for complete seasoning. When the
quarry sap evaporates, it leaves a crystalline film on the faces of the stone and makes them
weather resistant. The dressing before seasoning improves the weather resistance. As such, the
dressing, carving and and moulding, etc. should be done as early after quarrying as possible.