Techniques for Protection and Supporting Systems for Trenches

8/11/2019 Techniques for Protection and Supporting Systems for Trenches

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A short course

on

Techniques for Protection and Supporting systems for Trenchos

27 April to 1 May, 2014

Address: King Saud Street (Extension), Mazrouiyah Neighborhood, Dammam.KSA

Postal Address: P.O.BOX 8499, Dammam 31411Kingdom of Saudi Arabia

Website: www.hajrgroup.com, Email:[email protected]

Phone: 03-8334080 /8334090, Fax: +966-38340800


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Prevention is better than

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Give a man a fish he will eat for one day , teach him

how to fish he will eat forever

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osha

/http://www.osha.gov 9
http://www.osha.gov/http://www.osha.gov/


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Excavation

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First Presentation

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Second Presentation

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Excavations

29 CFR 1926.650-652 andAppendices A - F

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29 CFR 1926.650-652 and

Appendices A - F

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Program Outline

The Regulation: An OverviewGeneral Requirements

Definitions

Soil Mechanics and Soil Types

Soil Testing

Visual Site Evaluation

Protective Systems

Special Health & Safety Considerations

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The Regulation

Excavating is one of the most hazardousconstruction operations according to OSHA.

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General Requirements

Identification of soil types and utilities before

diggingDaily inspections

Soil classification

Special safety and health considerations

Protective systems

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General Requirements

Protective Systems

Required for excavations 5 feet or greater in

depth.

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Competent Person

The designated competent person should have and

be able to demonstrate the following: Ability to detect:

- conditions that could result in cave-ins;

- failures in protective systems;

- hazardous atmospheres; and

- other hazards including those associated with confined

spaces.

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Competent Person

The designated competent person should have: Authority to take prompt corrective measures to

eliminate existing and predictable hazards and to stop

work when required.

:

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Excavation

An Excavation is any man-made cut,

cavity, trench, or depression in an earthsurface that is formed by earth removal.

.

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Ingress & Egress

Ingress And Egress mean "entry" and "exit,"respectively. In trenching and excavation operations,

they refer to the provision of safe means for employees

to enter or exit an excavation or trench.

""""

.

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Ingress & EgressAccess to and exit from the trench require the following conditions:

Trenches 4 feetor more in depth should be provided with a fixed means

of egress.

Spacing between ladders or other means of egress must be such that a

worker will not have to travel more than 25 feet laterally to the nearest

means of egress.

Ladders must be securedand extend a minimum of 36 inches above the

landing.

Metal ladders should be used with caution, particularly when electric

utilities are present.

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Hazardous Atmosphere

Hazardous Atmosphere is an atmosphere that by reason of beingexplosive, flammable, poisonous, corrosive, oxidizing, irritating, oxygen-

deficient, toxic, or otherwise harmful may cause death, illness, or injury to

persons exposed to it.

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TrenchA Trench is a narrow excavation (in relation to itslength).

In general, the depth of a trench is greater than itswidth, and the width (measured at the bottom) isnot greater than 15 ft.

(

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Protective System

Protective System refers to a method of protecting employees from cave-ins, from material

that could fall or roll from an excavation face or into an excavation, and from the collapse ofadjacent structures.

Protective systems include support systems, sloping and benching systems, shield systems, andother systems that provide the necessary protection.

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Protective Systems

Shoring

Shielding

Sloping

Benching

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Shoring

Shoringis the provision of a support

system for trench faces used to prevent

movement of soil, underground utilities,

roadways, and foundations.

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Shoring

Shoring (or shielding) is used when the

location or depth of the cut makes sloping

back to the maximum allowable slope

impractical.

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Shoring Types

Shoring systemsconsist of posts, wales,

struts, and sheeting. Three basic types of

shoring are:

Timber

Hydraulic

Pneumatic

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Timber Shoring

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Hydraulic Shoring

The trend today is toward the use of hydraulic shoring, a

prefabricated strut and/or wale system manufactured ofaluminum or steel.

Hydraulic shoring provides a critical safety advantage

over timber shoring because workers do not have to

enter the trench to install or remove hydraulic shoring.

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Hydraulic Shoring

Other advantages of most hydraulic systems are that they:

Are light enough to be installed by one worker;

Are gauge-regulated to ensure even distribution of pressure along

the trench line;

Can have their trench faces "preloaded" to use the soil's natural

cohesion to prevent movement; and

Can be adapted easily to various trench depths and widths.

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Typical Aluminum Shoring

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Pneumatic Shoring

Pneumatic Shoringis similar to hydraulic shoring.

The primary difference is that pneumatic shoring

uses air pressure in place of hydraulic pressure.

A disadvantage to the use of pneumatic shoring is

that an air compressor must be on site.

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Pneumatic and Hydraulic Jacks

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Hydraulic System

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Screw Jack

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Screw Jack System

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Underpinning

Underpinning involves stabilizing adjacent structures,

foundations, and other intrusions that may have an impacton the excavation.

As the term indicates, underpinning is a procedure in which

the foundation is physically reinforced.

Underpinning should be conducted only under the

direction and with the approval of a registered professional

engineer.

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Shielding

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Trench Boxes

Trench Boxesare different from shoring.

Instead of shoring up or otherwise supporting the

trench face, they are intended primarily to shield

workers from cave-ins and similar incidents.

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Trench Boxes

The excavated area between the outside of the

trench box and the face of the trench should be assmall as possible.

The space between the trench boxes and the

excavation side are backfilled to prevent lateral

movement of the box.

Shields may not be subjected to loads exceedingthose which the system was designed to

withstand.

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Trench Shield

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Trench Shield, Stacked

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Sloping

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Type A Soil

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Type A Soil Short Term

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Type B Soil

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Type B Over Type A Soil

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Type A Over Type B Soil

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Type C Over Type A Soil

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Type C Over Type B Soil

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Type B Over Type C Soil

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Sloping & Shielding

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Slope & Shield

Trench boxes are generally used in open areas, but

they also may be used in combination with slopingand benching.

The box should extend at least 18 inches above the

surrounding area if there is sloping toward

excavation.

This can be accomplished by providing a benched

area adjacent to the box.

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Slope & Shield

Earth excavation to a depth of 2 feet below the

shield is permitted, but only if the shield is designedto resist the forces calculated for the full depth of

the trench and there are no indications while the

trench is open of possible loss of soil from behind or

below the bottom of the support system.

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Slope & Shield

Conditions of this type require observation on the

effects of bulging, heaving, and boiling as well assurcharging, vibration, adjacent structures, etc., on

excavating below the bottom of a shield.

Careful visual inspection of the conditions

mentioned above is the primary and most prudentapproach to hazard identification and control.

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Slope & Shield

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Slope and Shield

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Benching

There are two basic types of benching, simple

and multiple.

The type of soil determines the horizontal to

vertical ratio of the benched side.

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Benching

All subsequent benches must be below the

maximum allowable slope for that soil type.

For Type B soil the trench excavation is

permitted in cohesive soil only.

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B Soil Multiple Bench

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Slope and Bench

Maximum allowable slopes for excavations

less than 20 feet based on soil type and

angle to the horizontal are as follows:

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Excavations

OregonOSHA

Safe practices for small business owners and contractors


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How to dig your own grave

No protective

system Spoilstoo close

No meansfor enteringor exiting

Nohardhat

Excavatorbucket

overworker

www.orosha.org


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SC

About this document

Excavations Safe practices for small business owners and contractors is an

Oregon OSHA Standards and Technical Resources publication.

Thanks to the following individuals for advice and technical assistance.

Craig Hamelund, Oregon OSHA

Dianna Gray, Oregon OSHA

George Vorhauer, Oregon OSHA

Jerry Mothersbaugh, Oregon OSHA

Mike Riffe, Oregon OSHA

Rocky Shampang, Oregon OSHA

Ron Haverkost, Oregon OSHA Tim Marcum, Oregon OSHA

Special thanks to Mike Parnell, president, Wire Rope & Rigging

Consultants, for advice on safe rigging practices.

Thanks to the following individuals for crafting the nal document:

Layout and design:Patricia Young, Oregon OSHA

Editing and proofng:Mark Peterson, DCBS Communications

We want you to understand what you read

This guide comes with a plain-language guarantee! Let us know ifyoure not satised. Contact Ellis Brasch at [email protected] call 503-947-7399.

Piracy notice.Reprinting, excerpting, or plagiarizing any part of

this publication is fine with us!Please inform Oregon OSHA of your

intension as a courtesy.


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Contents

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

Excavations and trenches . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

Plan before you dig . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

The role of the competent person . . . . . . . . . . . . . . . . . . . . . . . . . 9

How cave-ins occur . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

How soil is tested . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

Protective systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

Getting in and out of an excavation . . . . . . . . . . . . . . . . . . . . . . . 18

Materials and mobile equipment . . . . . . . . . . . . . . . . . . . . . . . . . 19

Hazardous atmospheres . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

Water accumulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

Working with hydraulic excavators and backhoe loaders . . . . . . 22

Working near high-voltage lines . . . . . . . . . . . . . . . . . . . . . . . . . . 26

Stability and adjacent structures . . . . . . . . . . . . . . . . . . . . . . . . . . 27

Excavation requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28

Safe practices checklist . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29

Important terms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34

Oregon OSHA Services. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38


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5

Introduction

A cave-in can trap you within seconds and kill you within minutes.

Two cubic yards of soil weigh about 6,000 pounds. If youre buried,youll suffocate in less than three minutes. Even if you survive, theweight of the soil is likely to cause serious internal injuries.

But cave-ins arent the only dangers in excavation work. Lack ofoxygen, toxic fumes, explosive gases, and buried power lines are alsohazards. Unfortunately, many contractors who do excavation workstill think that its too expensive or takes too much time to provideappropriate safeguards.

Two cubic yards of soil weigh about 6,000 pounds!

3,000

pounds

3,000

pounds

How much does soil weigh?


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Excavations and Trenches

Dig a hole in the ground and youve made an excavation. Excavationscan be any size: wide, narrow, deep, or shallow.

A trenchis a narrow excavation, not more than 15 feet wide at thebottom. If you install formsor other structures in an excavation thatreduce its width to less than 15 feet, measured at the bottom, theexcavation is also considered a trench.

If you work in an excavation thats ve feet deep (or deeper) youmust be protected from a cave-in.

If a competent persondetermines that theres a potential for anexcavation to cave-in, you must be protected regardless of its

depth.

What is an excavation?

An excavation is a man-made cut, cavity, or depression in the earths surface.

Excavation

Open-faced excavation

Excavation cut into slope


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Trench

Deeper than wide

No more than

15 feet wide at

the bottom

What is a trench?

A trench is deeper than it is wide and not more than 15 feet wide at the bottom.

Typical trench

Trench created by formwork


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Plan before you dig

Planning reduces the chance that something will go wrong when youstart a job. Consider the following before you start excavating:

Debris near the excavation site that could create a hazard

How employees will get in and out of the excavation

How to protect people from falling into the excavation

How to respond to emergencies

Location of overhead power lines and underground utility lines(Call 811from anywhere in Oregon for help in locatingunderground utility lines)

Possibility of atmospheric hazards in the excavation Possibility of water in the excavation

Stability of soil at the excavation site

Stability of structures adjacent to the excavation site

Vehicles and other mobile equipment that will operate nearthe excavation

Weather conditions


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Soil and stability

Some soils are more stable than others. The type of soil is one of thefactors that determine the chance that an excavation will cave in. Thereare three basic soil types that you may encounter in Oregon:

Type A very stable. Clay is an example.

Type B less stable than type A soil. Crushed rock, silt, and soilsthat contain an equal mixture of sand and silt are examples.

Type C less stable than type B soil. Gravel and sand are examples.

Soil has other qualities that affect its stability. These include granularity,saturation, cohesiveness,andunconfined compressive strength.

Granularity refers to the size of the soil grains; the larger the grains, the lessstable the soil.

Saturation means how much water soil will absorb.

Cohesiveness means how well soil holds together; clay is a cohesive soil.

Unconned compressive strength is determined by a test that shows howmuch pressure it takes to collapse a soil sample. For example, type A soilmust have an unconned compressive strength of at least 1.5 tons persquare foot.


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How soil is tested

A competent person must conduct visualand manualsoil tests beforeanyone enters an excavation. Visual and manual tests are a critical partof determining the type of protective system that will be used.

Visual tests

Visual testing involves looking at the soil and the area around theexcavation site for signs of instability. The competent person mightdo visual tests such as the following:

Observe the soil as it is excavated. Soil that remains in largeclumps when excavated may be cohesive. Soil that breaks upeasily is granular.

Examine the particle sizes of excavated soil to determine howthey hold together.

Look for cracks or ssures in the faces of the excavation.

Look for layers of different soil types and the angle of the layersin the face of the excavation that may indicate instability.

Look for water seeping from the sides of the excavation.

Look for signs of previously disturbed soil from otherconstruction or excavation work.

Consider vibration from construction activity or highway trafcthat may affect the stability of the excavation.


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Manual tests

Manual testing involves evaluating a sample of soil from the excavationto determine qualities such as cohesiveness, granularity, and unconnedcompressive strength. Soil can be tested either on site or off site but

should be tested as soon as possible to preserve its natural moisture.Examples of manual tests:

Plasticity test.Shape a sample of moist soil into aball and try to roll it into threads about 1/8-inch indiameter. Cohesive soil will roll into 1/8-inch threadswithout crumbling.

Dry strength test.

Hold a dry soil sample in yourhand. If the soil is dry and crumbles on its own orwith moderate pressure into individual grains or nepowder, its granular. If the soil breaks into clumpsthat are hard to break into smaller clumps, it maybe clay combined with gravel, sand, or silt.

Thumb penetration test.This test roughly estimatesthe unconned compressive strength of a sample.

Press your thumb into the soil sample. If the sampleresists hard pressure it may be type A soil. If its easyto penetrate, the sample may be type C.

Pocket penetrometersoffer more accurate estimates of unconnedcompressive strength. These instruments estimate the unconnedcompressive strength of saturated cohesive soils. When pushed

into the sample, an indicator sleeve displays an estimate in tons persquare foot or kilograms per square centimeter.


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Protective systems

The basic methods for protection from cave-ins are sloping, benching,shoring, and shielding. The method you should use depends on factorssuch as soil type and water content, excavation depth and width, the

nature of the work, and nearby activities that could increase the risk ofa cave-in. The competent person has the responsibility for consideringthese factors and for determining the appropriate protective system.

A registered professional engineermust design protective systemsfor all excavations that are more than 20 feet deep.

Sloping and benching

Sloping and benching provide protection by removing material fromthe face of an excavation at an angle to its oor; in general, the atterthe angle, the greater the protection. Benches are cuts in the slope thatgive it a stair-step appearance. There are two types of benches: simpleand multiple.

Rain, vibration, and pressure from heavy equipment can make soil un-stable and increase the risk of a cave-in. Sloped or benched excavations

that show signs of cracks, bulges, or clumps of soil that fall away fromthe faces are dangerous and must be inspected by a competent person.

You must immediately get out of the excavation and stay away until thecompetent person determines it is safe to enter.

A registered professional engineer must determine the angle ofslopes in excavations that are deeper than 20 feet.


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What do benched slopes look like in type A, type B, and type C soil?

Type A soil: simple and multiple benches

Simple Bench Excavation Multiple Bench Excavation

Simple Bench Excavation Multiple Bench Excavation

Type B soil: simple and multiple benches

Type C soil: simple and multiple benches

Benching in type C soil requires a registered professional engineer.


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Shoring and shielding

Shoring and shielding systems can prevent cave-ins in excavationswith or without sloped or benched faces. The safest way to install andremove them is from outside the excavation.

Shoresare vertical or horizontal supports that prevent the faces of anexcavation from collapsing. Vertical shores are called uprights. Theyreeasy to install, relatively inexpensive, and often used in stable soil orin shallow excavations that have parallel faces. Vertical shores must besized for the excavations dimensions and soil type.

Horizontal shores are calledwalers. Walers are often used when un-stable soil makes sloping or benching impractical and when sheeting is

necessary to prevent soil from sliding into the excavation.Shieldsprovide employees a safe work area by protecting them fromcollapsing soil. Shields dont prevent cave-ins but shield workers if a

face does collapse. They are usually placed in the excavation by heavyequipment.

Shoring and shielding systems are available from manufacturers ina variety of dimensions, usually aluminum or steel, or they can be

custom-built fromtabulated data

approved by a registered professionalengineer. Manufacturers will also provide tabulated data with theirsystems that includes engineering specications, depth ratings, specialinstructions, and system limitations. Only by carefully studying andunderstanding the manufacturers tabulated data can the competentperson choose the correct protective system.


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What do shores and shields look like?

Vertical shore

Photo credit: Speed Shore Corp.Photo credit: Speed Shore Corp.

Horizontal shore

Photo credit: Speed Shore Corp.

Trench shield


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Getting in and out of an excavation

An excavation that has a depth of four feet or more must have ameans for entering and exiting such as a stairway, ladder, orramp within 25 feet of employees; their safety may depend on

how quickly they can climb out.

Structural ramps that are used to enter and exit the excavationmust have nonslip surfaces and be designed by a competent person.

A competent person must also evaluate ramps made from soil that areused to enter and exit an excavation.


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Hazardous atmospheres

Hazardous atmospheres can occur in excavations near landlls, sitescontaminated by leaking gas lines or storage tanks, in sewers, and inother conned spaces. If these conditions are possible, a competent

person must test for oxygen deciency (oxygen levels less than 19.5percent) and hazardous atmospheres before you can enter.


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Water accumulation

Water makes soil unstable. You cant enter an excavation when waterhas built up unless you are protected from the unstable soil. Protectionincludes specialized support systems and water-removal equipment. A

competent person must inspect the excavation and monitor methodsused to control water accumulation.


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Working with hydraulic

excavators and backhoe loaders

You can dig an excavation with a hand shovel or an excavator. Use ahand shovel improperly and you risk blisters. Use an excavator improp-erly and you risk a life. Too many workers are hurt because they dont

follow safe practices when they use hydraulic excavators and backhoeloaders. Most accidents happen for three reasons:

Entering the excavators swing area

Using quick-coupling devices improperly

Using unsafe rigging methods to drag a trench shield

Entering the excavators swing area

Be aware of the excavators swing area and blind spots. Always maintainat least three feet of unimpaired clearance between the excavators ro-tating superstructure and adjacent objects. Keep others outside the areaby marking it with rope, tape, or a similar barrier, if necessary.

Post warning signs that say DANGER STAY CLEARonall sides of the excavator.

Dont allow anyone to stand under a suspended load or the boom,arm, or bucket.

Keep the bucket as close to the ground as possible whenworkers are attaching loads.

Lower the boom to a safe position with the bucket on the groundand turn off the excavator before getting off.


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Where do I post the warning signs?

Post warning signs that say DANGER STAY CLEARon all sides of the excavator

[from Division 3, Subdivision O, 437-003-0090(1)]

Dont allow anyone to stand under the boom, arm, or bucket!

Photo credit: Robert I. Carr, Ph.D., P.E.


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Using quick-coupling devices improperly

Aftermarket quick-coupling devices make it easy to change bucketsor replace other attachments. However, a number of workers have beenkilled when the coupling devices have not been locked properly and the

buckets have detached. Manufacturers of quick couplers recognized thehazard and newer devices have locks that prevent buckets from detach-ing unintentionally, but not all users may be aware of the problem.Retrot locking pins are available for older equipment.

Follow the manufacturers instructions for using positive locks onquick-disconnect equipment.

Securely latch attachments such as quick-disconnect buckets beforebeginning work.

Make frequent visual inspections of quick-disconnect systems especially after changing attachments.

Using unsafe rigging methods to drag a trench shield

Using an excavator to drag a shield through a trench can put tremen-dous forces on rigging components. For example, the force requiredto drag a 10,000-pound trench shield through a narrow trench willincrease dramatically with resistance from the trench walls or from

plowing of the front of the shield. Know the slings rated capacitiesand never exceed them. The whiplash effect of a broken or improperlyrigged sling can kill anyone in its path.

Follow the instructions in the operators manual when using anexcavator to lift or move an object.

Lift and drag to move a trench shield horizontally in a trench;avoid plowing with the front of the shield. Plowing signicantly

increases the tension on the slings. Some manufacturers of trench shields warn workers to stay out of

the box while it is being moved. Always check the manufacturersrequirements.


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Stability and adjacent structures

Make sure that structures, roadways, and sidewalks adjacent to theexcavation are adequately supported.

Use an appropriate support system such as shoring or bracing if the excavation could affect the stability of nearby buildings, side-walks, and roads.

Dont excavate below the base or footing of any foundation thatmight endanger employees unless you do one of the following:

Use a support system that protects employees and keeps thestructure stable.

Ensure that the excavation is in stable rock.

Have a registered professional engineer determine that thestructure will not be affected by the excavation work.

Have a registered professional engineer determine that theexcavation work will not endanger employees.


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Excavation requirements

Oregon OSHAs Division 3, Subdivision P, Excavationrequirements applyto all open excavations.

1926.650 Scope, application, and denitions

1926.651 Specic excavation requirements

437-003-0096 Underground installations

1926.652 Requirements for protective systems

Appendix A Soil classication

Appendix B Sloping and benching

Appendix C Timber shoring for trenches

Appendix D Aluminum hydraulic shoring for trenches

Appendix E Alternatives to timber shoring

Appendix F Selection of protective systems


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1. A designated competent person at the excavation site

understands visual and manual test methods, use ofprotective systems, the hazards of excavation work, andthe requirements of Oregon OSHAs excavation standards.

2. A designated competent person inspects the excavation,adjacent areas, and protective systems daily before workbegins, as necessary throughout the shift, and after rain orother conditions that could increase the risk of a hazard.

3. A designated competent person has authority toimmediately correct hazards and to order employeesto leave the excavation until the hazards have beencorrected.

4. Sewer, telephone, fuel, electric, or water lines near thesite have been located and clearly marked. Contact the

Oregon Utility Notication Center for help in locatingunderground utility lines call 811 from anywhere inOregon.

5. Hard hats are required whenever there are overheadhazards.

6. Debris and other unnecessary material have been cleared

from the site.

Safe practices checklist

All your answers should be Yes! Yes No


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7. Employees who are exposed to vehicle trafc are providedwith and wear high-visibility garments.

8. Excavations at remote sites have appropriate warningbarriers.

9. Employees are protected from loose rock or soil that couldfall into the excavation.

10. Employees are prohibited from working or standing undersuspended loads.

11. Employees are required to stand away from vehicles thatare being loaded or unloaded.

12. Employees are prohibited from working on the faces ofsloped or benched excavations when other employees arebelow them.

13. Mobile equipment operators have an effective wayof knowing when they are too close to the edge ofan excavation. Examples include barricades, hand ormechanical signals, stop logs, or grading away from theexcavation.

14. Spoils, equipment, and tools are at least two feet from the

edge of the excavation.

15. Walkways that cross over excavations more that six feetdeep have standard guard rails and toe boards.

Yes No


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16. Underground installations are protected, supported, orremoved when the excavation is open.

17. Excavations that have a depth of four feet or more haveladders or other means of safe access within 25 feet ofemployees.

18. Ladders are secured and extend three feet above edge ofthe excavation.

19. A designated competent person designs the structural

ramps that employees use to enter and exit the excavation.

20. Structural ramps have nonslip surfaces.

21. Employees are prohibited from entering an excavationthat shows signs of water accumulation unless they areprotected from the risk of a cave-in.

22. A competent person monitors the methods used to controlwater from accumulating in an excavation.

23.

Surface water or runoff is diverted away from the excavation.

24. The atmosphere in an excavation is tested when thepossibility of a hazardous atmosphere exists.

25. Employees are protected from hazardous atmospheres oratmospheres containing less than 19.5 percent oxygen.

Yes No


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26. Emergency rescue equipment is available when hazardousatmospheres could exist in an excavation.

27. Employees who work in excavations are trained to useappropriate personal protective equipment.

28. A designated competent person has classied soil at theexcavation site with at least one manual test and onevisual test.

29. Materials and equipment used for protective systems atthe excavation site are chosen based upon soil analysis,excavation depth, and expected loads.

30. Materials and equipment used for protective systems areinspected regularly and in good condition.

31. Damaged equipment is removed from service immediately.

32. Protective systems are installed without exposingemployees to the risk of cave-ins.

33. Structures, roadways, and sidewalks adjacent to theexcavation are adequately supported.

34. Excavations are backlled when protective systems areremoved.

Yes No


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35. Appropriate sloping, shoring, or shielding protectsemployees who work in excavations ve or more feet deep.

36. A designated competent person determines the typeof shield used at a site by considering factors such asthe nature of the work, excavation dimensions, soilcharacteristics, and equipment used to lower or positionthe shield.

37. Employees in excavations more than 20 feet deepare protected by a system designed by a registered

professional engineer.

38. Shields are installed so that they do not move laterally.

39. Employees are not allowed in shields that are movedvertically.

Yes No


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Important terms

Adjacent The area within a horizontal distance from the edge of a vertical-sidedexcavation equal to the depth of the excavation.

Aluminum hydraulic shoring

A pre-engineered system of aluminum hydraulic cylinders (cross braces)and vertical rails (uprights) or horizontal rails (walers). Designed to supportthe faces of an excavation.

Benching A method of sloping the sides of an excavation by forming a series of steps.

Cave-in The separation of a mass of soil or rock from the face of an excavation intoan excavation.

Competent person

A person capable of identifying existing and predictable hazards in thesurroundings or working conditions and who has authorization to takeprompt corrective measures to eliminate the hazards.

Cross brace Horizontal member of a shoring system installed perpendicular to the sidesof an excavation, the end of which bears against uprights or wales.

Excavation A man-made cut, cavity, or depression in the earths surface.

Face The side of an excavation.

Hazardous atmosphereAn atmosphere that could cause an injury or illness. Examples: explosive,ammable, poisonous, corrosive, oxidizing, irritating, oxygen decient, ortoxic.

Previously disturbed soilSoil that has been disturbed from excavation work or other digging. Soilcannot be classied type A if it has been previously disturbed. Use visualtests to identify previously disturbed soil.

Protective systemA system designed to protect workers in excavations. Sloping andbenching, shores, and shields are examples of protective systems.

Ramp An inclined walking or working surface constructed from earth or fromstructural materials such as steel or wood.


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Registered professional engineerA professional engineer registered in the state where the work isperformed. A professional engineer registered in any state can approvedesigns for manufactured protective systems or tabulated data used ininterstate commerce.

Sheeting Component of a shoring system that prevents soil from sliding into anexcavation.

Shield A structure able to withstand forces caused by a cave-in. Shields can bemanufactured or custom-built in accordance with 1926.652(c)(2)-(c)(4).Shields are also called trench boxes and trench shields.

Shore A structure that supports the sides of an excavation and prevents cave-ins.

Sloping A method of inclining the face of an excavation to minimize the risk of a

cave-in. The maximum allowable slope varies with soil type, environment,and work done at the excavation site.

Soil Weathered rock, gravel, sand, or combinations of clay, silt, and loam.

Stable rock Natural solid mineral material that can be excavated with vertical sides andwill remain intact while exposed.

Structural ramp A ramp made of steel or wood, usually for vehicle access. Ramps madefrom soil or rocks are not considered structural ramps.

Support system A system that supports an adjacent structure, underground installation, orthe face of an excavation.

Surcharge A load exerted on ground adjacent to an excavation.

Tabulated data Tables and charts, approved by a registered professional engineer, used todesign and construct a protective system. At least one copy of the data andthe name of the engineer who approved it must be kept at the site whilethe system is constructed.

Trench An excavation that is longer than wide. In general, the depth is greaterthan the width but the width measured at the bottom of the trench is notgreater than 15 feet.

Upright The vertical member of a shoring system.


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Notes


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ServicesOregon OSHA offers a wide variety of safety and health services to employers and employees:

Portland

1750 NW Naito Parkway,Ste. 112Portland, OR 97209-2533503-229-5910Consultation: 503-229-6193

Salem1340 Tandem Ave. NE,Ste. 160Salem, OR 97303503-378-3274Consultation: 503-373-7819

Eugene1140 Willagillespie, Ste. 42Eugene, OR 97401-2101541-686-7562Consultation: 541-686-7913

Bend

Red Oaks Square1230 NE Third St.,Ste. A-115Bend, OR 97701-4374541-388-6066Consultation: 541-388-6068

Medford1840 Barnett Road, Ste. DMedford, OR 97504-8250541-776-6030Consultation: 541-776-6016

Pendleton721 SE Third St., Ste. 306Pendleton, OR 97801-3056541-276-9175Consultation: 541-276-2353

For more information, call the Oregon OSHAofce nearest you.

Salem Central Ofce350 Winter St. NE, Rm. 430Salem, OR 97301-3882Phone:503-378-3272

Consultative Services Offers no-cost on-site safety and health assistance to help

Oregon employers recognize and correct workplace safety

and health problems. Provides consultations in the areas of safety, industrial

hygiene, ergonomics, occupational safety and healthprograms, assistance to new businesses, the Safety andHealth Achievement Recognition Program (SHARP), andthe Voluntary Protection Program (VPP).

Enforcement

Offers pre-job conferences for mobile employers inindustries such as logging and construction.

Provides abatement assistance to employers who havereceived citations and provides compliance and technicalassistance by phone.

Inspects places of employment for occupational safety andhealth hazards and investigates workplace complaints andaccidents.

Appeals, Informal Conferences Provides the opportunity for employers to hold informal

meetings with Oregon OSHA on concerns about workplacesafety and health.

Discusses Oregon OSHAs requirements and clariesworkplace safety or health violations. Discusses abatement dates and negotiates settlement

agreements to resolve disputed citations.

Standards & Technical Resources

Develops, interprets, and provides technical advice onsafety and health standards.

Provides copies of all Oregon OSHA occupational safetyand health standards.

Publishes booklets, pamphlets, and other materials to assist

in the implementation of safety and health standards andprograms.

Operates a Resource Center with video lending library,books, technical periodicals, and consensus standards.

Public Education & Conferences Conducts conferences, seminars, workshops, and rule

forums. Coordinates and provides technical training on topics

such as conned space, ergonomics, lockout/tagout, andexcavations.

Provides workshops covering management of basicsafety and health programs, safety committees, accidentinvestigation, and job safety analysis.

Manages the Safety and Health Education and Training GrantProgram, which awards grants to industrial and labor groupsto develop training materials in occupational safety andhealth for Oregon workers.

Toll-free:800-922-2689Fax:503-947-7461en Espaol:800-843-8086Web site:www.orosha.org


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Youtubes links for Trenches and Exacavation

http://www.youtube.com/watch?v=UHuyMZIhukI

http://www.youtube.com/watch?v=ovNJIkJgp4Q

http://www.youtube.com/watch?v=kFOPDH5NTWY

http://www.youtube.com/watch?v=aNSEg6ToE1g

http://www youtube com/watch?v=OFc7Fy8awbs
http://www.youtube.com/watch?v=UHuyMZIhukIhttp://www.youtube.com/watch?v=UHuyMZIhukIhttp://www.youtube.com/watch?v=ovNJIkJgp4Qhttp://www.youtube.com/watch?v=ovNJIkJgp4Qhttp://www.youtube.com/watch?v=kFOPDH5NTWYhttp://www.youtube.com/watch?v=kFOPDH5NTWYhttp://www.youtube.com/watch?v=aNSEg6ToE1ghttp://www.youtube.com/watch?v=aNSEg6ToE1ghttp://www.youtube.com/watch?v=OFc7Fy8awbshttp://www.youtube.com/watch?v=OFc7Fy8awbshttp://www.youtube.com/watch?v=OFc7Fy8awbshttp://www.youtube.com/watch?v=aNSEg6ToE1ghttp://www.youtube.com/watch?v=kFOPDH5NTWYhttp://www.youtube.com/watch?v=ovNJIkJgp4Qhttp://www.youtube.com/watch?v=UHuyMZIhukI

Techniques for Protection and Supporting Systems for Trenches

Documents

Transcript of Techniques for Protection and Supporting Systems for Trenches