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CE337 Construction safety management > topic 3: excavation safety > Flashcards

topic 3: excavation safety Flashcards

1
Q

Is any man-made cut, cavity or depression
in an earth surface that is formed by earth
removal.

A

EXCAVATION

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2
Q

The fatality rate for excavation work is ()% higher than the rate for general construction.

A

112%

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3
Q

Is a narrow excavation where the depth of a trench is greater than its width, and the width measured at the bottom is not greater than 15 ft.

A

TRENCH EXCAVATION

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4
Q

() require a protective system, unless if the excavation is made entirely of stable rock. If less than 5ft, no protective system required.

A

Trenches 5 ft (1.5m) deep or greater

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5
Q

() required a protective system designed by a registered professional engineer

A

Trenches 20 ft. (6.1m) or deeper

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6
Q

Eliminate hazards and control risks by implementing precautions in excavations and trenches with: (4)

A

Excavation Safety
1. pre-planning
2. protective systems
3. safety measures
4. inspections

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7
Q

Hazards of Excavation Works (5)

A
  1. Soil Collapse
  2. Falling Objects
  3. Underground Utilities
  4. Working Surfaces
  5. Confined Space Conditions
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8
Q
  • A () is a mixture of rock, water, air and a variety of other substances
  • () is made up of rock in the form of small particles and spaced called voids.
  • Normally, some parts of the voids are filled with water.
A

soil

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9
Q

Types of soil collapse: (5)

A
  1. sliding
  2. bulge
  3. toppling
  4. boiling
  5. heave
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10
Q

Types of soil collapse

Soil shifts downwards along a slip plane, often
caused by excessive loading or water saturation weakening the soil structure.

A

Sliding

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11
Q

Types of soil collapse

Soil deforms outward, creating a protruding area, typically due to internal pressure or lateral forces from excavation or nearby construction.

A

Bulge

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12
Q

Types of soil collapse

Soil or rock tips over around a pivot point,
commonly caused by undercutting or destabilizing forces at the base.

A

Toppling

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13
Q

Types of soil collapse

Soil is displaced upward due to water pressure,
often caused by high groundwater pressure or rapid infiltration disrupting soil stability.

A

Boiling

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14
Q

Types of soil collapse

Soil rises and expands, usually due to moisture
changes such as wetting and drying cycles or freezing and thawing, which affect soil volume.

A

Heave

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15
Q

Principal Causes of Soil Collapse (5)

A
  1. Steep cutting angle
  2. Super imposed load
  3. Shock and vibration
  4. Water Pressure
  5. Drying
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16
Q

In General, excavation means loosening and taking out materials, leaving space above or below ground. In Civil Engineering, this is usually performed during the
Earthworks phase.

Each type of soil has a certain level of risk for collapsing, and corresponding safety measures.

A

Principles of Soil Collapse

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17
Q

Soil types (4)

A

Stable rock
Type A
Type B
Type C

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18
Q

Description: Natural solid mineral matters
Examples: Rock, hilly terrain

A

Stable rock

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19
Q

Description: Cohesive soil with unconfined compressive strength of 1.5 tons per square foot or greater
Examples: Clay, slit sandy clay

A

Type A

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20
Q

Description: Cohesive soil with strength greater than 0.5 tsf but less then 1.5 tsf
Examples: Angular gravek (similar to crushed rock)

A

Type B

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21
Q

Description: Cohesive soil strength 0.5 tsf or less
Examples: Granular soil such as grave, sand & loamy sand

A

Type C

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22
Q

Stable rock:
Max Slope (H:V)
degrees

A

vertical
90 degrees

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23
Q

Type A
Max Slope (H:V)
degrees

A

3/4:1
53 degrees

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24
Q

Type B
Max Slope (H:V)
degrees

A

1:1
45 degrees

25
Q

Type C
Max Slope (H:V)
degrees

A

1-1/2:1
34 degrees

26
Q

This involves the use of supports or structures to prevent the collapse of soil and provide stability to excavation sites.

A

Shoring

27
Q

Shoring systems can include: (3)

A
  • Hydraulic Shoring
  • Metal Shoring
  • Adjustable Shoring
28
Q

Uses hydraulic pressure to support the excavation walls. This type can be adjusted as needed and is often used in deeper excavations.

A

Hydraulic Shoring

29
Q

Uses steel plates and beams to provide support. It’s durable and can be used in a variety of soil conditions.

A

Metal Shoring

30
Q

Consists of adjustable props and struts that can be modified to accommodate changes in the excavation depth.

A

Adjustable Shoring:

31
Q

This is an older method where wooden planks and beams are used to support the sides of an excavation.

A

Timbering

32
Q

Timbering involves: (2)

A

Timber Sheeting
Timber Bracing

33
Q

Wooden planks are placed vertically against the excavation walls to prevent soil from collapsing.

A

Timber Sheeting:

34
Q

Wooden beams are used to brace and support the timber
sheeting or excavation walls.

A

Timber Bracing

35
Q

Sheeting - ()cm x ()cm
Wales - ()cm x ()cm
Struts - ()cm x ()cm

A

Sheeting - 5cm x 15cm
Wales - 10cm x 15cm
Struts - 10cm x 15cm

36
Q

Before Shoring or Timbering, the walls of an excavation shall be stripped of loose rocks or other materials that might slide, roll, or fall on workers.

Every excavation over 1m shall be kept free of water at all times.

A

OSHS RULE 1413: EXCAVATION

37
Q

Excavation over 1m deep shall be supported by
adequate shoring and timbering. This shall not apply
to such excavation if:
* A worker is not required to enter for any purpose
* Cut in solid rock
* Walls are sloped to 45 deg. from the vertical or cut to the angle of repose.

Shoring or timbering in excavation over 6.1m deep
shall be designed by a structural engineer and
approved by the proper authority.

A

Provision of Shoring and Timbering (OSH Rule 1413: Excavation)

38
Q

refers to the use of protective systems designed to safeguard workers and equipment from the risks associated with soil collapse during excavation activities. Unlike shoring and timbering, which actively support and
stabilize the excavation walls, () involves creating a protective barrier to prevent soil from falling into the excavation area.

A

Shielding/Boxing:

39
Q

A safe distance from the edge of excavation.
() are constructed in order to prevent erosion and
sedimentation, and in some cases as a means to
provide for a safe working environment during
excavation by controlling surface runnoff

Minimum (): Not less than 1/3 of depth of
excavation.

A

Berms

40
Q

A berm of reduced width of not less than 1m may be allowed if:

A
  • Materials being excavated are stable
  • Shoring to carry the additional load
  • Barriers are provided to prevent roll back of excavated material
41
Q

Prevention of falling materials
* () should be provided
* () must be posted to prevent the public from going near the excavation

A

Barricades
Signs

42
Q

Provision for Barricades
The top of the walls of an excavation more than () shall be barricaded to a height of at least ()

A

2m deep
1m

43
Q

Prevention of fall: Surface Crossing of Trenches

A
  • Walkways or bridges must be provided
  • Minimum clear width of 20 in.
  • With standard rails
  • Extended a minimum of 24 in. past the surface edge.
44
Q

Working Surface
* Excavation shall be kept () at all times
* In muddy areas, workers should be provided with () to reduce the hazard of slipping.

A

free of water
boots

45
Q

Underground Facilities
Determine the () of underground facilities and take
necessary steps to prevent damage to these facilities

A

location

46
Q

() causes extreme geotechnical problems in
excavations such as sand running for most of construction projects such as tunneling.

A

Groundwater

47
Q

Two Major Methods for Controlling Groundwater: (2)

A

Pumping Technique
Exclusion Technique

48
Q

() involves digging a sump where groundwater collects, which is then simply drawn out using a pump

A

Pumping Technique

49
Q

() - achieved by constructing an impermeable or low permeability cut-off wall to keep the groundwater out of the excavation

A

Exclusion Technique

50
Q

CAN EXCAVATION BE A CONFINED SPACE?
Oxygen-deficient atmosphere: less than () oxygen

A

19.5%

51
Q

CAN EXCAVATION BE A CONFINED SPACE?

Potential for other gases to be present include but not limited to
* () from potential leaks or cut lines
* () from decayed matter

A

natural gases
methane

52
Q

CAN EXCAVATION BE A CONFINED SPACE?

Test for atmospheric hazards like low oxygen levels and presence of hazardous fumes and toxic gases is required when the excavation is ()

A

4 feet deep or greater

53
Q

Working in Excavation

  • check excavation permit
  • protect all underground installations
  • remove trees, boulders, stump and other surface emcumbrances and hazards before starting excavation.
A

Prior to Opening

54
Q

Working in Excavation

  • wear goggles and hard hats
  • store excavated materials at least 1m from edge
  • remove boulders or other materials that may roll
  • do not stockpiles materials or store equipment near edge or excavation
  • give special attention to side slops, adversely affected by weather, moisture content or vibration
  • in case of undercut, safely support overhanging materials
  • safe working distance between workers
  • control groundwater
  • provide walkways, bridges, guardrails, barricades, warning
  • flags/lights for pedestrian and vehicular traffic
A

During Operations

55
Q

Working in Excavation

  • shore and brace sides of excavation to resist superimposed loads if
  • necessary to operate equipment above or near excavation
  • use stop logs, warning signs, or barricades if mobile equipment is utilized adjacent to excavations.
  • use horn or give signals to ensure safety
A

Equipment Operations

56
Q

Working in Excavation

  • check the atmosphere condition before entry
  • do not wok alone in a confined space
  • provide life line
  • provide ventilation or blower before entering
  • provide emergency rescue equipment such as breathing apparatus, safety harness line, and basket stretcher
A

Excavation in Confined Space

57
Q

Working in Excavation

  • during break time, workmen should never stand or take rest on high banks of soft material
  • maintain guardrails, fences, or other barricades and warning lights from sunset to sundown.
  • do not leave tools, materials, or debris in walkway ramps or near the edge of excavation
  • do not use guardrails as resting place
A
58
Q
  • Daily, before start of each shift
  • Every part of an excavation over 2m deep where workers work
  • shall be inspected by the person in charge at least once a day.
  • This must be performed by a competent person
  • After heavy rain
  • When fissures, tension cracks, undercutting, water seepage, occur at the bottom
  • when there is a change in size, location, or placement of spoil pile
  • when there is any indication of change or movement in adjacent structures.
A

Inspection

59
Q

an individual who is capable of identifying existing predictable hazards or working conditions that are unsanitary or dangerous. (e.g. safety officers)

A

Competent person

CE337 Construction safety management (8 decks)

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