As used in this chapter:
(a) "Blast area" means the following:
(1) For well holes. The area included within a distance equal to the greatest burden of any single hole contained in each blast, such distance to be measured in all directions;
(2) For toe holes and block holes. The area included within a distance equal to the horizontal measurement of the combined area to be detonated, such distance to be measured in all directions, but not less than thirty-five feet.
(b) "Blaster" means the person in possession of a valid permit for blasting purposes.
(c) "Superintendent" (or equivalent) means the person designated by the contractor to be in charge of construction operations at a given location. Included in such definition is a person so designated by any subcontractor.
(d) "Contractor" means the person engaged in any construction operations involving the use of explosives for blasting purposes.
(e) "Delay firing" means the detonation by a special blasting cap or mechanical device in which the period between successive detonations initiated by such cap or device is of the order of thousandths of a second.
(f) "Primary blasting" means the extraction of a mineral volume from the original nature body or bed by the use of explosives in open pit, side hill, through cut, tunnel and shaft construction. Included in such definition is toe and seam shooting.
(1) "Toe shooting" (snake-holing) means removing through the use of moderate quantities of explosives loaded in small diameter holes, ledge or high bottom that remains after a main primary shot.
(2) "Seam shooting" means removing loosened or overhanging material from the rock face by the use of explosives.
(g) "Secondary blasting" means the reduction of oversize material by the use of explosives to facilitate shovel operations. Included in such definition is mud capping, block-holing and trenching.
(1) "Mud capping" (adobe blasting, dobying) means the firing of a quantity of explosives on or against a rock, boulder or other object without confining the explosive in a bore hole.
(2) "Block-holing" means the fragmentation of boulders through the firing of a small quantity of explosives that has been loaded therein in a small diameter bore hole.
(h) "Sprung" means the enlargement of a bore hole with a moderate quantity of explosives in order that larger quantities of explosives may be inserted therein for the main primary blast.
(i) "Stemming" means the suitable inert incombustible free-flowing material of a relatively small size consistent with the size of the hole and used in confining explosives in a bore hole.
(j) "Displacement" means the amount of ground motion measured in fractions of an inch.
(k) "Velocity" means the rate at which the ground or earth particle vibrates, measured in inches per second.
(l) "Acceleration" means the measure of force exerted by the vibrating earth particle measured in g’s. The acceleration of gravity (g) is 32.2 feet per second.
(m) "Frequency" means the number of oscillations of the ground or earth particle that occur in one second, tabulated in cycles per second (c.p.s.).
(n) “Energy ratio” means the measure of the kinetic energy of the vibrating earth particle. It is defined as follows:
Energy ratio-(a/f)2
a - acceleration in feet per second squared (not in g’s)
f - frequency of the vibration tabulated in cycles per second
(o) "Components of motion"means the ground motion, measured in three mutually perpendicular components, namely:
(1) Longitudinal or radial motion;
(2) Traverse motion; and
(3) Vertical motion.
(p) "Longitudinal or radial" means the motion along a line joining the shot point and the point of observation.
(q) "Transverse" means the motion at right angles to a line joining the shot point and the point of observation.
(r) "Vertical" means the motion up and down.
(s) "Seismograph" means the instrument for measuring ground motion. It may be a displacement-type, a velocity-type or an acceleration-type instrument.
(t) "Millisecond" means one one-thousandth of a second.
(u) "Safe limit of vibration" means that any one of the three mutually perpendicular components shall be based on a peak particle velocity of two inches per second, or an equivalent displacement-frequency relationship, or acceleration-frequency relationship, or energy ratio value. The ground vibration shall not exceed these limits in the immediate vicinity of any structure. The safe limit of the vibration index shall be that developed by the United States Bureau of Mines and published in its Report of Investigation 5968 and any supplement thereto.
(v) "Explosive" means any chemical compound or mechanical mixture that is intended for the purpose of producing an explosion, that contains any oxidizing and combustible units or other ingredients, in such proportions, quantities or packing that an ignition by fire, by friction, by concussion, by percussion or by detonator of any part of the compound or mixture may cause such a sudden generation of highly heated gasses that the resultant gaseous pressures are capable of producing destructive effects on contiguous objects or of destroying life or limb.
(w) "Charge weight" (W) means the weight in pounds of an explosive charge.
(x) "Actual distance"(D) means the distance in feet from the blast to the nearest structure.
(y) "Delay interval" means the time interval in milliseconds between successive detonations of an explosive.
(z) "Scaled distance" means the actual distance in feet divided by the square root of the maximum charge weight per delay for delay intervals eight milliseconds or greater:
Scaled distance - distance = D
Maximum charge per delay W
(Ord. 1978-71. Passed 6-13-78.)
Next Doc