City of Ottawa Explosives Information Session 2012 Explotech Engineering Rene “Moose” Morin,...

City of OttawaExplosives

Information Session 2012Explotech Engineering

Rene “Moose” Morin, P.Eng.Jeff Corace, P.Eng.

Presentation Schedule

Federal, Provincial and Municipal Regulations

Explosive Products

Blast Operations Overview

Blast Design

Blast Vibration and Overpressure

Hazards of Blasting

Public relations

Why Blasting?

Efficient Reduction of Construction Time vs.

Mechanical Breakers

EffectiveConsistently effective in large variety of

geological conditions

EconomicalCost effective method of Rock Excavation

Unfortunately…..

Blasting represents an inconvenience to day-to-day activities of neighbors.Blasting attracts a great deal of attention from nearby occupants and homeowners.Blasting tends to create concern in neighbors, producing an increased number of damage complaints.Blasting requires special safeguards to be in place.

Despite the intuitive belief that sounds and vibrations from blasting operations are an

indication of increased damage potential or safety

concern, such is not the case.

Module I

Federal, Provincial and Municipal Regulations

Storage and Transportationof Explosives

Storage of Explosives

Governed by the Explosives Regulatory Division (ERD) of Natural Resources Canada (Federal). Storage of explosives for mining is generally governed by the Province or Territory in question and closely follows Federal Regulations.


Quantity/Distance charts have been established so that all explosives storage is at a safe distance from any location where people may gather, residences, roads, churches, railways, etc.

Explosives and detonators must be stored separately.


Careful inventories must be maintained for each product in each magazine, the area around the magazine must be kept clean, as must the magazine.

Magazine

Storage of Explosives on Urban Projects

On local projects, explosive and detonators are delivered and removed daily. Temporary storage can be in “Day Boxes” or more commonly, pick up trucks with separate compartments for explosives and detonators.

Storage of Explosives on Urban Projects

Regardless of the set up, storage boxes and pickup truck containers should be locked and the truck keys removed when not retrieving explosives or detonators.

Day Box

Typical Local Delivery Unit

Transportation of Explosives

Transportation of Explosives

The Department of Transportation’s Dangerous Goods Division regulates transportation of explosives and detonators.

Requirements for Transportation

No person shall handle, offer for transport or transport dangerous goods unless he/she is a trained person, or is performing those activities under the direction of a trained person.

A trained person shall have in his/her possession at all times a certificate of training for the Transportation of Dangerous Goods.Every explosive shipment must have with it a “Shipping Document.”

Shipping Document


1. The transportation vehicle must meet the standards of an MTO licensed mechanical safety check.

2. Smoking on or around the vehicle is prohibited.

3. A fully charged and accessible fire extinguisher will be carried.

4. The vehicle must be attended at all times.


5. The carrying box must be fully enclosed, lockable and used only for high explosives; if detonators are carried, an approved barrier between the high explosives and detonators is necessary.

6. Quantity of explosives cannot exceed 80% of the vehicle’s carrying capacity.

High Explosive Placard

Detonator Placard

Pickup For Local Delivery

Typical Local Delivery Unit

Bulk Truck

Explosive Transport Vehicles

Provincial Regulations


In Ontario, construction projects are governed by “The Occupational Health and Safety Act and Regulations for Construction Projects”, June 2000 (Section 196 – 206 for surface blasting works).

The Ontario Standard Specification OPS120 is often incorporated into municipal and MTO specifications.


For blasting at mines and Quarries, the MOE Model Municipal Noise Control Bylaw NPC 103 and 119 apply.

Limits ground vibrations to 12.5mm/s and overpressures to 128dBL when routinely monitored.

MOE limits are nuisance based criteria as opposed to damaged based criteria


The Ontario Provincial Standard, OPSS 120 (April 2008) is often applied to projects in its original or modified state.

Includes requirements for designs, submissions, pre-blast inspections, monitoring, etc.

Limits vibrations to 50mm/s (>40Hz) and 20mm/s (<40Hz). No limit for overpressure.

Current City of Ottawa spec F1201 implements a modified OPSS 120

Provincial RegulationsEffective September 2004, Surface Blasting has been established as a licenced trade. However, the licence is not mandatory in the Province of Ontario

Ottawa Regulations / By-laws

Currently no blasting by-law or permit in the City (repealed in 2004)

F1011 – Addresses pre-construction inspections. Applied to City contracts.

F1201 – Use of Explosives – Amended OPS120 amended.

For private developments, blast control documentation is typically a condition of site plan approval.

Module II

Explosive Products

Types of Explosives

Explosives

M ili ta ryE xp lo siv es

C o m m e rcia lE xp lo siv es

E xp lo siv es

H igh E xp lo siv esC ap -S e ns it ive

B las ting A g en tsC a p- Insen s it ive

C o m m e rcia lE xp lo siv es

Explosives

W atergel BlastingAgents

ANFO/Polystyrene MixtureANFOPS

Alum inised ANFOALANFO

ANFO Em ulsion(Heavy ANFO)

Blends

Am m onium Nitrate Fuel O ilANFO

Em ulsion BlastingAgents

Blasting AgentsCap-insensitive

Explosives

Dynam iteN itro glycerin B ased

(NG )

W atergelC ap-S ens itive

E m uls ionC ap-S ens itive

C ast P rim ers

H igh E xp lo s ives

Explosives

Explosives

Short D elay (m s)Long D elay (LP)

E lectric C aps(D etonators)

Short D elay (m s)Long D elay (LP)

N onelectric C aps(D etonators)

E lectronic C aps(D etonators)

D etonating C ord

EXPLOSIVES ACCESSORIES

Emulsions

Derive their sensitivity from the microscopic particle size of their components and tiny air voids trapped within the mixture.Perform well in harder rocks.Often used to prime less sensitive explosives such as ANFO.Offers excellent water resistance

Dynamite (NG)

Typically consists of a mixture of nitroglycerine, Nitroglycol, nitrocellulose, oxidizing salts (AN) and fuel.NG content varies from 5% to 90%Can be water resistantPackaged according to field application – convolute shells, spiral wound shells, plastic shells.

ANFO

Consists of AN Prill mixed with fuel oil (typically 6% fuel oil by weight).

Typically the most cost effective explosive available.

Effective in softer rocks (Limestone).

Poor water resistance.

Requires priming.

Other types of explosive

Gels

Slurries

TNT

PETN

Initiation Systems

Initiation systems are a combination of explosive devices and accessories designed to convey a signal and initiate an explosive charge from a safe distance.

Signal function can be either electric or non-electric.

Types of Initiation Systems

Electric

Non-electric Shock tube

Electronic

Detonating cord

Initiation systems

Selection of system to employ depends on:

Type of explosiveTemperatureGeologyHydrostatic pressureEnvironmental constraints

Millisecond Delay blasting

Improves rock fragmentation

Improves rock displacement

Limits vibration

Decreases blast noise

Decreases rock throw

Reduces powder factor

Millisecond Delay Blasting

For electric and non-electric shock tube systems, the delay period is pre-set inside the detonator using a pyrotechnic fuse.

For electronic detonators, the delay period is programmed on site using a computer chip inside the detonator.

Cap scatter is a problem with electric and non-electric detonators. Not a problem with electronic detonators.

Electric

Utilizes an electrical power source with circuit wiring to convey electrical energy to detonators which in turn fire and initiate the explosive.Modern electric detonators include an internal feature to prevent electrostatic energy from accidentally initiating the detonator.All detonators are configured with a pre-set delay period.

Non-Electric

Utilizes chemical reactions to convey an impulse signal to the explosives.

Two principal types of Non-electric systems are available:

Shock Tube Detonating Cord

Shock Tube

The inner surface of the shock tube is coated with a thin layer of explosive (Al and HMX).

Typically set up with surface and down the hole delays to sequence the blast and avoid cutoffs.

Electronic

Uses computer chip to implement delay.

Greatly improved delay accuracy

Ability to program the detonator after loading

Detonating cordManufactured with an explosive core of PETN encased in a textile and plastic jacket.Available in a variety of grades specified according to core loading of number of grains per foot (7000grains=1lb)All grades are cap sensitive and have detonating velocities of approximately 6200m/s.Detonation of the cord in or adjacent to high explosive loaded in a hole will initiate the blast. Detonating cord on the surface causes problems with air blast.

Module III

Blast Design and Safety

Site Safety

Over the past century, blasting has been made safer with the advent of safer products.

However, blasting accidents still occur, often with fatal results.

Proper training of personnel, including licencing programs represents one of the most effective means of improving site safety today.

Definitions

Blast Site: is the area within which blasting crew is performing or have performed drilling, loading and tying.

Blast Area: is the exclusion area required to be cleared by the blaster-in-charge and his assistants to prevent accidental injuries to workers and the public.

• Designed by an experienced, competent person in compliance with the contract requirements as well as all applicable regulations and bylaws

Blasts are to be:

Design Phase

• Designed to ensure the safety of the public and workers and to mitigate the risk of property damage

Design Phase

• To be prepared in accordance with To be prepared in accordance with requirements of the OHSA.requirements of the OHSA.

• Identify the areas to be evacuated.Identify the areas to be evacuated.

• Where areas cannot be evacuated, adjust the Where areas cannot be evacuated, adjust the blast accordingly.blast accordingly.

• Blast area shall be clear of workers and public Blast area shall be clear of workers and public prior to the blast. prior to the blast.

Blast Program

Establish Site evacuation/Safety plans

Blast Program

• Blasting mats shall be used appropriately, where required

• Warning horn or siren, which is audible to public and/or workers shall used.

• Blast shall be designed to be appropriate to the blast area (residential, rural, commercial etc.)

Protective measures:

In the event of a “bad blast”:

• Determine the likely reasons for this result.

• Document the actions to be taken and blast redesign to prevent a recurrence.

Blast Program

Module IV

Hazards of Blasting

Environmental:Blast Vibrations and Blast Overpressure annoy people.

On most urban projects, although damage is very unlikely, an inordinate amount of time is spent answering phone calls from irate neighbours assuring them that there is no danger.

Hazards of Blasting

Hazards of Blasting

Physical:Blast Vibrations: Very high vibration levels from close-

in blasting may cause damage to weaker or highly stressed construction materials.

Physical:Blast Overpressure:Very high levels (>140 dB) may on

rare occasions cause damage to highly stressed windows, for example, but climactic conditions are generally far more destructive.

Hazards of Blasting

Physical:Flyrock:Flyrock is described as material which

is ejected from the blast area and can cause damage or even fatalities and so it is extremely important that Flyrock be controlled.

Hazards of Blasting

Typical Flyrock Causes

Geology and rock conditions

Carelessness

Improper design

Typical Flyrock Causes

Blast Design

• Powder factor too high

• Inadequate burden

• Too short a stemming region

• Failure to use stemming

• Improper delays between rows

• Wrong blasthole delay sequence

• Short holes

Module V

Blast Design

Mechanics of a Blast

Controllable VariablesDrilling accuracy

Blasthole size

Amount of explosives per delay period

Drill pattern

Explosive(s) type

Delay sequencing

Charge geometry (by decking)

Number of holes per blast

Blasting frequency

Uncontrollable Variables

Local geology

Production requirements

Distance to existing structures to be protected

Rock characteristics

Excessive moisture (standing water)

Detonation process

Detonation produces hot gas and pressure

Rock around borehole is crushed and cracks extend outward.

Gases extend into the cracks breaking and moving the rock, utilizing most of the energy available in the process. A small amount of energy escapes in the form of ground and air vibrations.

A small amount of energy escapes in the form of ground and air vibrations.

This energy is in the form of elastic waves – there is no further damage to the rock nor any permanent displacement of rock particles outside of the blasted area a distance of approximately 20 borehole diameters

Blast Designs

Blast Layout Terminology

Burden: Horizontal distance between a borehole and the quarry faceSpacing: Horizontal distance between holes; perpendicular to the burden.Subgrade: Depth of holes below the final grade level.Collar:Length of unloaded borehole at the top of the hole.Stemming: Inert material placed on top of explosive column or between “decks”.

Drilling Parameters

S = SpacingB = BurdenH = Hole DepthT = Stemming (Collar)J = Sub-drilling

HB T

J

S

Drill Patterns(Square B = S)

Burden (B)

Spacing (S)

Free Face

NonelectricEZ-Det/Handi-DetInitiation System

Surface Delay(17, 33, 42 ms)

Clip

Surface Connector

In-the-holeDelay (500 ms)

SurfaceDelay (25 ms)

Shock-Tube

EZ-Det/Handi-Det Cap

Grade Rock / QuarryV-Cut Sequence

F R E E F A C E

50 25 0 42 67 92

134 109 84 126 151 176

218 193 168 210 235 260

Start

42

4242

42

42

Initiation Sequence - Dice Five“Trench”Free Face

25 25

50

75 75

125 125

100

25 MSDelay

Start

Controlled Blasting Techniques

Preshear, Postshear

Line drilling

Typical Detonation Sequence

Not to Scale - For Illustration Purpose Only

Preshear holes fired approx. 200 ms prior to production and buffer holes

Production and buffer holes to be fired approx. 200 ms after the presplit holes are detonated

Remaining Preshear holes to be detonated with the next blast

Controlled …..

Line Drilling

Holes are drilled along the perimeter at close spacing prior to blasting.

Holes are not loaded

Production blast is used to fracture rock within the excavation area to the line drilled perimeter.

Tends to provide the best final face but drilling costs are elevated.

Care must be taken not to ‘hit’ the walls too hard and fracture rock beyond the neat line – may require the application of buffer holes.

Controlled …..

Module VI

Blast Vibration and Overpressure

The derivatives of blasting which cause the greatest amount of concern to property owners adjacent to blast sites are flyrock, ground vibrations and overpressure (air blast).

Blast Vibrations

The magnitude of ground vibrations is expressed in terms of Peak Particle Velocity in mm/s. Peak Particle Velocity is generally accepted world wide as the best way to express the potential for damage from blast vibrations.Peak Particle Velocity is defined as the rate of exchange of the amplitude. This is the speed of excitation of the particles in the ground resulting from vibratory motion caused by blasting.

Basis for Vibration ControlBlast vibration control is almost universally based on research undertaken by the United States Bureau of Mines as reported in publication RI8507.This research and associated data represents the most extensive information available directly relating blast induced damage to particle velocities.This research established threshold vibration intensities for different materials found in typical residential construction below which damage is highly improbable.

Basis for Vibration Control

The “Z” curve graph and associated criteria are extremely conservative and have been consistently proven to be such through countless additional research efforts undertaken in the years since the publication of RI8507.

It has formed the basis for the majority of regulations and guidelines worldwide, including those established by the City of Ottawa and MOE.

Scientifically observed damage as a result of blast induced has never been observed at ground motions below the Z-Curve limits.

Blast OverpressureBlast overpressure is a compressional wave in air caused by:

1. an air pressure pulse caused by the direct rock displacement at the face or collar of a blast hole.

2. A rock pressure pulse caused by the vibrating ground.

3. A gas release pulse caused by explosives gases escaping through fractures in rock.

4. A stemming release pulse caused by gas escaping from blown out stemming.

Blast Overpressure

Blast overpressure is usually low frequency although there can be a high frequency component (noise). Overpressure is measured in dB(L).

Overpressure is far more difficult to control when compared to ground vibrations and is heavily dependent on environmental conditions. As such, limits on overpressure are rarely imposed on

construction projects.

Wind Speed vs. Overpressure

WIND EQUIVALENT

(Kph)

OVERPRESSURE

STANDARDS(dB) (Kpa)

650 180 20.68 Structural Damage525 176 13.79 Plaster Cracks250 164 3.45 Most Windows Break115 150 0.62 Some Windows Break

65 140 0.21

OSHA Maximum For Impulsive Sound.

This level could cause loose windows to vibrate.

THRESHOLD OF PAIN

32 128 0.05M.O.E.E. Guideline for

Monitored Blasts15 115 0.01 Complaints Likely

6.5 1002.07 x 10-

3 Pneumatic Hammer

0.65 602.07 x 10-

5 Conversational Speech

0.02 02.07 x 10-

8 Threshold of hearing

147dBL

150dBL

140dBL

Measurement of Blast vibrations

Seismographs monitor on a continual basis and record both ground vibration and overpressure intensities.

These records allow reliable, accurate, legal documentation of blast effects and analytical tools for advanced analysis if required.

Why NOT monitor

Cost

Outside of revenue stream

Outside of regular duties / no qualified technician

Equipment unavailable

Don’t see benefit / repercussions

Never had a problem

Inconvenient / Don’t care / can’t be bothered

Why bother monitoring?

Proper documentation has legal status.

Provides quantitative, scientific backup for public perception – Humans are not accurate seismographs.

Good records form an integral part of the damage investigation procedure.

Compliance Monitoring – Ground vibrations

Sensor should be installed on or in the ground at the closest ‘structure’ on the side closest to the blast.If ground installation is not feasible, couple to structure within 300mm of the surrounding ground.Install sensor within 3m of the structure.Ensure suitable coupling of sensor – bolted, buried, spiked sandbagged.

Compliance monitoring – Overpressure

Sensor should be installed at the closest ‘structure’ on the side closest to the blast.

Avoid placement near reflective surface.

Avoid shielding by other buildings, trees, etc.

Microphone height does not affect reading.

What constitutes a good record?

Record should include: Time and date Location of seismograph Vibration intensities in 3 mutually

perpendicular planes Overpressure Vibration waveforms and frequencies Name of operator Calibration check

All vibrations records and blast reports should be maintained and filed for future reference to be incorporated into the damage investigation procedure.

Missing, incomplete or faulty vibration and blast data all contribute to a difficult damage investigation procedure and public discontent

Understanding the Event Report

Autonomous Vibration Monitoring (AVM)

Autonomous Vibration Monitoring (AVM)

Couples internet with seismographsAutomatic event distributionAVM Package Vibration Monitor Modem (cellular or land line) Power source Data processing system Website/cell phone/e-mail

AVM TelemetryBlast Occurs

SeismographTriggers

Event Transm

itted to

IPS

Through Phone Network

IPS Resets Unit a

nd

Starts Monito

ring

AVM Data Processing

IPS ProcessesXML and WMF Files

XML and WMF Files Transmitted

And VerifiedFor Processing

FPS UpdatesWeb Page

FPSCreates GIF and

PDF

Event Sent to

Cell Phone or Email

Web User Interface

Secure site (HTTPS)View vibration dataUser based filters

Web User Interface

Sort Events by Date/Job/unit

Web User Interface

Download options Filter events PDF, GIF, Blastware file

Web User Interface

Notification methods Cell phone text message email

Sample text message

Human Response to Blast Vibrations and Overpressure


Human beings are very sensitive to blast vibrations.

Vibrations as low as 0.5 mm/sec are perceptible and annoying to some people.


Blast overpressure may only be noticed because windows, knick knacks or doors may rattle. This is caused by the low frequency impact which blast overpressure applies to buildings having a resonant frequency of 10 – 15 Hz.

Blast overpressure rarely causes blast damage but at levels of 115 dB or more complaints increase.

Module VII

Public Relations

Public AwarenessWhy do people get upset? They were not informed of the blasting They do not understand why they need to blast They do not understand regulatory vibration limits Believe that if they can feel the vibrations, there

MUST be damage to their home Annoyed by the development or construction

activities Stress in their own personal and professional lives

What you can do to ease the public concerns

Notify public of blasting operations (visible signs and written notices)

Educate and explain instead of dismissing concerns - Provide literature, web sites and videos explaining construction blasting.

Explain your monitoring program.

Provide access to blast records: event reports, threshold levels for damage to structures.

Promptly address complaints or concerns.

Listen to their concerns.

PR Components of a proper Blast Control Plan

Pre-blast inspections

Vibration / Overpressure monitoring

Provide a means of efficiently and effectively addressing public concerns and questions.

Address Damage complaints in a timely manner.

Pre-blast Inspections

Pre-Blast Inspections

F-1011 (March 2011) Pre-Construction Inspections All structures within 30m of general work

F-1201 (March 2011) Pre-Blast Inspections All structures within 65m of blasting operations


Inhabitants of buildings close to blasting may feel vibrations from the operation and as a result, become much more conscious of many of the previously unnoticed cracks, water stains, and similar defects in their homes and offices. Pre-blast inspections are intended to provide a representative sampling of pre-existing deficiencies which are present in every residence.

These inspections are not intended to provide a detailed, exhaustive list of every crack present.

In the event of concern by residents with regards to possible damage as a result of the construction, the pre-construction inspections are used to form the basis for an investigation.


Damage Complaints

Regardless of how well a blasting operation goes, there will inevitably be complaints from at least some residents in the area. This is due to a variety of factors including:

Public disapproval with the project. Public annoyance due to the construction. Dishonest owners. General public unfamiliarity with blasting.

Fears expressed concerning blasting damage are often a result of the sensitivity of the human body to vibration, especially in the low frequency range.

Inhabitants of buildings close to the blasting may feel vibrations from the operation and as a result, become much more conscious of many of the previously unnoticed cracks, water stains, or similar defects

Damage Investigations

Regardless of the perceived frivolousness or credibility of a complaint, all complaints should be addressed.This may be as simple as a visit to discuss the matter with the owner or may require more in depth analysis.In any case, damage investigations should be performed by qualified individuals independent from the affected parties (owner/ contractor).


If required, a full damage investigation should incorporate:

Visual inspection and documentation of the damaged area.

Comparison with pre-blast inspections. Analysis of Vibration data. Analysis of Blast reports Review of applicable related research.

Damage InvestigationsAll significant impacts on the residence should be included as part of the investigation

Differential thermal expansion, structural overloading, chemical changes in building materials, shrinkage and swelling of wood, fatigue and aging of building materials, foundation settlement and the impacts of human habitation all induce transient deformation similar to those induced by construction operations.


Damage reports are typically submitted to the blast contractor and complainant.

Copies of the report should be provided to the Project Contract Administrator if requested.

The adoption of a properly planned, controlled and executed blast program can lead to project results which are viewed as successful by the project owners, contractors, and affected adjacent residents alike.

Questions?

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