excavation · b. mechanical excavation: the excavation work using any electrical or mechanical what...

EXCAVATION What is excavation ? Marking a hole or tunnel by digging the ground by man or machine is called excavation

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Excavation hazard 1. Striking buried services / Underground

utilities.

2. Collapse / cave-ins.

3. Hazardous substances/Flammable & / or toxic gas release.

4. Lack of Oxygen or asphyxiation.

5. Flooding.

6. People or objects falling in.

7. Collapse of adjacent structures.

such as pipelines and electrical cables, are a potential hazard during excavations.

Before any excavation can begin, you must call concern department .Utility operators will mark underground utilities to verify their location before you begin to excavate the worksite to prevent accidental damage.

Underground utilities,

Many excavation fatalities are because of cave-ins.

Cave-ins pose the greatest risk and are much more likely to result in worker fatalities than other excavation-related accidents.

cave-ins

Workers die when they cannot breathe because the weight of collapsed materials prevents their chest from expanding.

Chest constriction prevents your body from taking in oxygen and releasing carbon dioxide.

Hazardous substances

Airways

Lungs

Diaphragm

When oxygen deficiency or a hazardous atmosphere exists or could exist in an excavation greater that 4 ft. in depth, the atmosphere must be tested before workers enter.

Oxygen deficient atmospheres are atmospheres that contain less than 19.5% oxygen.

oxygen deficiency

Take precautions to prevent water from collecting in an excavation. This is done by designing:

Diversion ditches

Dikes

Pumps

Other ways to stop water from building up within an excavation

Flooding

Precautions

• Battering • Shoring • benching • Prevention of striking buried services • Excavation area should be suitable barricade • Good lighting • Avoid heavy vehicle coming near the sides • Issue permit before start the work • Ladders shall be provided every 7.5 meters (25 feet) of

lateral travel in the trench • Ladders shall be securely supported at the bottom as well

as at the top • Gas test by the competent person.

Requirement

Daily and before the start of each shift.

As dictated by the work

being done in the trench.

After every rain storm and

other events that could

increase hazards, e.g.,

snowstorm, windstorm,

thaw, earthquake, etc.

Inspections – Competent Person

Frequency of testing should be increased if equipment is operating in trench as well as if welding, cutting, or burning is done in trench.

Inspections

Walkways provided when crossing over excavation.

Standard guardrail

installed when more

than 6 feet above

a lower level.

Fall Protection

What is shoring?

A structure that supports the sides of an excavation and protects against cave-ins.

What is Battering ?

The sides of the excavation can be sloped back (battered) at an angle that is sufficiently shallow that the soil will not slip.

What is Benching

Benching system means a method of protecting employees from cave-ins by excavating The sides of an excavation to form one or a series of horizontal levels or steps, usually With vertical or near-vertical surfaces between levels.

Timber Shoring

Aluminum Hydraulic

Trench Boxes

Pneumatic Systems

Type of excavation A. Manual Excavation: The excavation without using any powered

equipment.

B. Mechanical Excavation: The excavation work using any electrical or mechanical

What is the maximum distance between two adjacent accesses in a long excavation?

answer: A ladder must be present within 25feet, of employees working in excavation.

In open excavation – At least every 30m on the perimeter, if less than 1.2m deep.

At every 7.5m on the perimeter, if more than 1.2m deep.

Stable rock Type A

Classify the soil type:

Type B Type C

Cohesive soil

Clay, or soil with a high clay content, which has cohesive strength

Does not crumble

Can be excavated with vertical side slopes

Plastic when moist

Hard to break up when dry

Definitions

Granular soil

Gravel, sand, or silt, with little or no clay content

No cohesive strength

Cannot be molded when moist

Crumbles easily when dry

Note: Some moist granular soils exhibit

apparent cohesion

Definitions

Unconfined compressive strength

Load per unit area at which a soil will fail in compression

Note: Estimated in the field by use of a pocket penetrometer, thumb penetration test, and other methods

Definitions

Soil slope

• Roll into thread

• At least 2 inches in length

• Longer unbroken thread means more cohesive

Thread Test

• Roll soil into a cigar shape

• Pinch between thumb and finger

• Longer ribbon means more cohesive

Ribbon Test

Thumb Penetration Test

Pocket Penetrometer

Access and egress

Excavation

Ramp, ladder or stairs required at 4 feet or deeper.

25 feet 25 feet

Test at 4 feet if suspected

Hazardous Atmospheres

• LEL

• Oxygen

• CO

• H2S

• Petroleum

• Other toxics

Personal protective equipment (PPE) that may be required depending on the type of work includes:

Hard hats

Protective footwear

Gloves

Safety glasses with sideshields

Hearing protection

Fall protection

PPE

Emergency rescue equipment must be readily available where hazardous atmospheric conditions exist or expected to develop during work.

• Breathing apparatus

• Safety harness and line

• Basket stretcher

Emergency Rescue Equipment

Emergency Rescue Equipment

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Badshah

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