STONE DUST BARRIERS
1. GENERAL:
1.1 Stone dust barriers shall be placed in the full path of the explosion and the shelves
shall be so arranged that their collapse in the event of an explosion is not impeded.
• 1.2 Barriers shall be sited as low as convenient within the upper third of the roadway;
and no part of any shelf and no stone dust on it shall be less than 10 cms. from the roof
or sides of the roadway or any roadway support. In addition, the shelves shall be
constructed and installed that, in the event of an explosion, they fly without obstruction
along the roadway.
2. DESIGN OF BARRIERS:
• 2.1 The stone dust shall rest on boards which run longitudinally in the roadway and
whose length equals the width of the shelves. These boards shall rest on a rigid frame,
the two members of which shall be at least 15 cms. in depth and rest on their edge on
two fixed rigid brackets.
• 2.2 Neither the boards nor the frame shall be fastened either to each other or to the
fixed brackets.
• 2.3 Primary or first or light barriers which are intended to be installed nearest to be a
possible point of ignition, when installed, shall consist of lightly loaded shelves (see
below) not more than 35 cms. in width.
• 2.4 The distance between two shelves of a light barrier shall be not less than 0.9 m.
and not more than 2.0 m.
• 2.5 The shelves of a light barrier shall be loaded with not more than 30 kg. of dust
per metre of shelf length and the total quantity of stone dust in the barrier shall be less
than 110 kg. of stone dust per sq. metre cross-section.
• 2.6 Secondary or heavy type of barriers (see below) intended for use further outbye
shall consist of one third of its shelves lightly loaded and spaced (see below) as in
case of primary barriers.
• 2.7 The loading for a heavy barrier shall be 390 kg. per sq. metre of the cross-section.
The shelves shall not exceed 50 cms. in width and their loading shall not exceed 60
kg. per metre of shelf length.
• 2.8 The distance between heavily loaded shelves or between a heavily loaded shelf
and a lightly loaded shelf shall not be less than 125 cms. and not more than 270 cms.
• 2.9 The lightly loaded shelves shall be adjacent to each other and placed at the in bye
end of the barrier.
• 2.10 Where circumstances require intermediate barriers, such barriers shall be loaded
with 195 kg. of dust per square metre of roadway, half the dust being placed on lightly
loaded shelves and half of heavily loaded shelves. The lightly loaded shelves being
arranged at the inbye end, as in the case of heavy barriers.
• 2.11 When calculating the quantity of stone dust in a barrier, cross sectional area
shall mean the average cross sectional area determined by an offset survey of the
roadway where the barrier is installed. The amount of stone dust in the lightly loaded
shelves in a heavy barrier shall be calculated proportionately on the basis of average
length of the shelf as determined from the offset survey plan.
• 2.12 For maximum dispersibility the dust shall be piled loose on the shelves. The
dust shall also be of a type that will not cake in use; in damp or wet condition waterproofed stone dust shall be used.
• 2.13 Where a roadway has to be enlarged to provide sufficient height to
accommodate a barrier, the ripping shall extend over a distance on each side of the
barrier equal to at least 20 times the difference between the height of the top of the
stone dust on the barrier and the height of the unripped roadway.
• 2.14 When sitting a barrier, the distance as specified shall be measured from the shelf
nearest to the face.
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