How is Birblast Controlled?

Airblast is controlled mainly by the proper use ofstem-ming material (the drill cuttings or crushed stones that areshoveled back into the blasthole after the expiosYvemate^rial^has been loaded to a predetermined depth from thesurface), and by not loading explosives into portions of

with cracks, voids or mud seams. These techniquesminimize the escape of gases and confine the explosiveenergy where it is needed to efficiently break rock.

What are the Ground Vibration andAirblast limits?

The United States Bureau of Mines (USBM) conductedextensive research over a 35-year period on the effects ofblast-induced ground vibration and airblast on residentialstractures. This research produced recommended limitsthat, if adhered to, will effectively protect residentialstructures from damage, even if the Masting is repeatedon a daily basis over a period of many years.

How do we know if these Vibration andBirblast levels are Safe?

Seismographs are used to measure vibration and airblasts effects. These scientific instmments take thehuman opinion out of the measurement and give exactmeasurements on each blast. With science and tech-nology today, blasters are able to predict the vibrationand air blast limits before putting off a blast. The Stateof Illinois limits levels for vibration and air blasts.These measurements are taken by an independentthird party to verify compliance with these regula-trons. These seismic consultants will measure eachblast detonated at this location to insure that the vibra.tion levels are safe.

If Vibrations or Uirblasts are Felt at mvhouse does this mean I have damage?

Ninety-nine percent of the time damage to a structuredoes not occur just because the vibrations or air blastsare felt. Humans are much more susceptible to vibra-tions and air blasts than structures. The surprise of ablast being detonated creates a much more adverseeffect than the actual blasting. A person in a homewith a lot of noise within the house (kids, TV, stereo)may not even notice that a blast has been detonatedwhere as an extremely quite home may feel the ef-fects. A person outside of the house may not evenknow that the blast has been detonated while someoneinside the house will be able to tell that a blast hasbeen detonated. The air blast from blasting operationsoften causes doors or windows to rattle slightly thusmaking the homeowner aware that a blast has beendetonated. The air blast is the most noticeable effectof blasting and is the least likely to cause any damage.Many activities within homes produce more vibrationsthan blasting operations. Normal door slamming andchildren running through the house produce more vi-brations than blasting operations. The movement pro-duced in structures on a daily basis by expansion andcontraction properties often results in movement to thestructure which is many times greater that blastingoperations. The only accurate way to measure vibra-tion intensity is with a seismograph

Tel: 614-771-4855Fax: 614.771.5159

Email: chicago@saulsseismic.com

PO Box 6359

Vernon Hills, IL 60061

Blasting-Dangerous or Not?

Each day in Illinois, nearly half a million pounds ofexplo-sives are_ safely detonated in quarries and surface coalm"1"'. with""the news °fl'lte- most PeoP'e inexperi-enced in the use of explosives have the opinion that explo.sives are used to destroy structures. From all of the newsthat we see

these days, thisjs the only use that the general public seesof explosives. To the contrary, commercial explosives areused to do work everyday. On a daily basis thousands'ofpounds of explosives are detonated safely in the constmoti°.n'-min"lg' md 1uaITyillg industries. Commercial explo-sives are used on a daily bases to fragment rock and i

environmental effects of vibration and noise at safelevels in surrounding areas.

Blasting operations are planned such that most of the ener-gy in the explosives is used to break rock. The energy thatis not used to break the rock goes into environmental ef-fects

such ^ as vibration and air blast. As the vibration wavestravel away from the blast site, the energy of these vibra^tion waves decreases with distance. These'vibration wavescm not be seen but can be felt at surrounding structures".The blast are calculated such that the energy ofthevibra-tmn waves do not cause damage to surrounding structures.These vibration waves travel on the surface of the groundand as a result the structures located underground Iweib,pools, pipelines, septic tanks) are not likely'to be effectedby vibrations. In most cases the actual movement of theground is less than .05 inches (which is about the width ofa human hair). Realistically speaking, if there is a potenttialofany blast causing damage to surrounding structures,that blast will be changed

Why is Blasting Necessary?

Blasting is the most cost effective way to fracture rock sothat it can be excavated by earth-moving equipment. This.in turn, reduces the costs of building materials, such asgravel and concrete, energy produced from coal, and manyother products derived from limestone, coal and otherminerals.

Who May Conduct Blasting?

Only a certified blaster may conduct blasting in Illinois'quarries and surface coal mines. To become certified, ablaster must obtain 2 years of blasting crew experienceincluding on-the-job training, attend 30 hours of ciass-room training, and pass an exam covering blast design,safety, vibration control and monitoring, and state andfederal blasting regulations. Once certified, t~b\astamust attend 24 hours of continuing education duringevery 3-year renewal period.

What Causes Ground Vibrationand How is it Measured?

??e.^,T_blast ?et°nates- some °! the explosive energynot utilized m breaking rock travels through the ground-I!-ai-?rections ^ 'yav!! motion. similar to the ripplecreated in a pond when a stone hits the water. 'This.^a''-e^°t10"; or 8r°llnd "ibration, travels mainly alongthe surface at speeds of 5,000 to 10.000 feetper-second°depending upon the density and thickness of the rockand soil. Its energy level decreases rapidly with distancefrom the blast and normally decays to levels undetecta-ble by humans beyond several thousand feet. Becauseexplosives are expensive and vibration represents wast-cd energy, it is to the blaster's advantage to utilize asmuch of the energy as possible in fragmentation, thcre-by minimizing vibration. Blasting seismographs areused to measure ground vibration in terms of paniclevelocity, which is the speed at which each particleTn'theground oscillates as the wave motion passes. This wouldbe similar to measuring the speed of a fishing bobbcr ina pond .u it moves up and down when a ripple passesunder it. Particle velocity is measured in inches per sec-ond, but beyond several hundred feet from a Uast'theactual movement of the ground, or displacement, is gen-erally only a tiny fraction of an inch, about the thickrossof apiece of paper, or less. So it is important to under.stand that a particle velocity reading expressed in inchesper second refers to the speed at which the groundmoved, and not the amount of movement.

How is Ground Vibration Controlled?

Blasters control ground vibration mainly by limit-mS the weight of explosives detonated within any8-millisecond period of time. They do this byusing millisecond delay detonators (blasting caps")to separate the firing time of each hole from adja-cent holes. In a typical 50-hole blast, the resultwould be 50 smaller and separate explosions in-stead of one large blast. A common'misconcep-tion is that the number of blastholes determinesthe resulting intensity of vibration. However.given the same charge weight per delay (poundsof explosives detonated within any 8-ms period)and the same distance, a 100 hole blast can bedesigned to produce no more vibration than a 10-hole blast.

What is Airblast and How is it Measured?

^ When a blast detonates, some energy is lost to the at-mosphere in the form of noise and/or concussion. Thisphenomenon is caused by the venting of gases throughcracks and fissures and the upward and outward move-ment of the rock on top and in front of the blastholes." res"Itme irwease in the air pressure is commonlycalled airblast. Like ground vibration, airblast levelsdecrease rapidly with distance from the blast. Howev-er, airblast travels only at the speed of sound, around1.100 feet per second, depending upon air temperature,and can be greatly influenced by "wind direction andspeed, and by atmospheric temperature inversionswhich can bend it back toward the earth and focus itsenergy several miles away. Airblast is usually mcas-ured with a special microphone connected to the sametype of seismograph that measures ground vibration.The most common units of airblast measurement arepounds per square inch (psi) and the decibel (d1B),which is based on a logarithmic sound-pressure scalerelated to human hearing..