Struck by Falling Objects - Workplace Safety and Health Council

PREFACE
This compilation of case studies on fatalities in the construction industry
is initiated by the Workplace Safety and Health Council, and put together
by the WSH Construction Committee in collaboration with the Ministry
of Manpower. This booklet depicts how the accidents occurred and
provides valuable learning points on how they may have been prevented.
This is the first in a series of such booklets to be published.
As much as the next few years promise to be exciting for the construction
industry, they also pose a great challenge to the industry to maintain
workplace safety and health. Construction sites have customarily been
viewed as high-risk workplaces, which more often than not have a higher
incidence of workplace fatalities. We must address this perception and
change the reality. While construction workers strive to complete a building
or facility, it is important that they do not risk life and limb. It is crucial
that these workers go home safely after work each day.
This booklet of case studies offers insights to all in the industry on how
these tragic accidents occurred, so that we may glean important, lifesaving
lessons from the experience. In learning from our past mistakes,
we can and must prevent these mishaps from happening again. Together
with your help, we can transform construction sites into safe and healthy
workplaces for our workers.
Mr Lee Tzu Yang
Chairman
Workplace Safety and Health Council

Struck by Falling Objects
Case 1 Pinned by a brick wall 64
Case 2 Pinned by a collapsed roof slab 67
Case 3 Struck by falling beams 70
Case 4 Struck by steel beams 73
Case 5 Struck by falling material in a trench 76
Case 6 Struck by a crane boom 78
Case 7 Hit by a collapsed wall 81
Case 8 Hit by steel rebars 84
Case 9 Buried under collapsed soil 87
Case 10 Crushed by a collapsing boom 90
Case 11 Struck by falling timber 92
Case 12 Struck by a falling crane boom 95
Case 13 Struck by a collapsed wall 97
Electrocution
Case 1 Electrocution by a faulty residual circuit breaker 100
Case 2 Killed by an exposed electrode holder 103
Struck By or Against Objects / Machines
Case 1 Hit by a scissors lift platform 108
Case 2 Hit by a moving vehicle 111
Case 3 Hit by a moving crane 114

STRUCK BY FALLING OBJECTS

CASE 1
PINNED BY A BRICK WALL
Description of Accident
A worker was constructing a new
drain inside an excavation in front
of a building under construction.
While he was leveling the concrete
for the new drain, a brick wall
(left behind from the old drain)
collapsed from the side of the
excavation and pinned him
under it, killing him on the spot.
Causes and Contributing
Factors
• The brick walls were constructed
on both banks of the old drain
to retain the soil.
• Before constructing the new
drain, one bank of the old drain
was removed and the area was
excavated so as to facilitate
the construction process. The
other bank was not removed
as it did not obstruct the
construction of the new drain.
1. A staircase in the worksite
2. The section of brick wall that sank
3. The excavation
4. Formwork for the second section of the
drain was to be constructed here
5. The new retaining wall
6. This side of the brick wall was removed
7. Formwork for the first section of the drain
1. Site of accident
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Struck By Falling Objects

• Investigations revealed that the
collapse of the brick wall was due
to soil movement in the
excavation compounded by
the heavy rain prior to the
accident. The main contractor did
not provide shoring for the
existing brick wall to prevent
it from collapsing into the
excavation when the workers
were working inside the
excavation.
Root Cause Analysis
Evaluation of loss
Type of contact
• One worker killed
• Caught between or under object
Immediate cause(s) • Inadequate guards or barriers
Basic cause(s)
Failure of SMS
• Inadequate assessment of loss exposure
• Inadequate leadership and/or supervision
• Inadequate work standards
• Hazard analysis and risk assessment
• WSH training and competence
• WSH inspections
Follow-up
A Stop Work Order was issued to the main contractor, which required
them to rectify the safety contraventions and to also engage a
professional engineer to carry out detailed soil investigations
and to develop a method statement for the construction of the
new drain as well as shoring for the excavation.
Struck By Falling Objects 65

Recommendations
Check the integrity and strength of any retaining structure prior
to an excavation.
Remove any brick wall, if present, prior to a reconstruction.
During a downpour, cover and protect all uncompleted concreting
work or brick-laying work with plastic or canvas sheets. The same
practice should apply for excavated trench sides and stockpiles
of excavated soil. No one should be allowed to be in the vicinity.
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Struck By Falling Objects

CASE 2
PINNED BY A COLLAPSED ROOF SLAB
Description of Accident
The accident occurred during the
demolition of an automated teller
machine (ATM) kiosk. After the
supporting walls of the kiosk
had been largely demolished,
the roof slab collapsed under its
own weight and a worker was
pinned underneath it.
Causes and Contributing
Factors
• The roof slab was resting on and
supported by three brick walls
of the ATM kiosk.
1. The collapsed roof slab
2. The remaining rear portion of the
left brick wall
• Demolition of the brick walls
was carried out without providing
any shoring to support the
weight of the roof slab and
prevent it from collapsing.
• After the brick walls were
demolished, the roof slab was
left without any support and it
crashed down under its own
weight.
• The worker was standing under
the roof slab when it collapsed
on him.
1. The roof slab of the ATM kiosk involved
in the accident
2. The deceased was pinned under the
slab here
3. The front end of the roof slab (marble
cladding removed)
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Root Cause Analysis
Evaluation of loss
Type of contact
Immediate cause(s)
Basic cause(s)
Failure of SMS
• One worker killed
• Caught between or under object
• Inadequate guards or barriers
• Inadequate leadership and/or supervision
• Inadequate work standards
• Lack of knowledge
• Hazard analysis and risk assessment
• WSH practices and procedures
Follow-up
The main contractor has to engage a professional engineer to
conduct a hazard analysis and develop a method statement for the
outstanding reinstatement work.
The bank concerned indicated that they will engage a professional
engineer to develop the method statement for all future demolition
of ATM kiosks.
A circular was sent to all banks with ATMs to alert them of the
circumstances leading to this accident and to urge them to play a
more proactive role to provide relevant information to their
contractors before work commencement.
68 Struck By Falling Objects

Recommendations
Shore the roof slab prior to the demolition of brick walls.
Alternatively, demolish or remove the roof slab first before
the walls.
Carry out a thorough inspection by a competent person to determine
the ATM kiosk’s structural arrangement prior to work commencement
especially if there are no construction drawings of the ATM kiosk.
Conduct continuous inspection by a competent person during the
demolition of the ATM kiosk to detect the hazards of any collapsing
structure (roof slab) resulting from weakened supporting brick walls.
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CASE 3
STRUCK BY FALLING BEAMS
Description of Accident
A stack of steel beams were
placed near an excavated area.
The beams toppled and landed
into the excavated area where
two workers were working.
One worker was killed and
another was injured.
Causes and Contributing
Factors
• Steel beams were to be installed
as supporting structures for the
excavation.
1. The injured worker was tasked to clean
mud on the sheet pile
2. The deceased was tasked to weld a
metal plate onto the sheet pile
3. Sheet pile
• The beams were placed about
350mm away from the excavated
area and each beam weighed
about 500kg.
• The steel beams were not placed
in a stable manner and were
very close to the edge of the
excavated area.
1. Excavation started from here
2. The 24 ‘I’ beams that were stored
directly above the place of work
3. Place of accident
4. Toppled beams
5. Excavation ended here
6. Excavator was shifting these metal
plates prior to accident
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• Digging work within the
excavated area might have
destabilised the stack of steel
beams and vibrations from the
excavators further contributed
to the instability.
• The main contractor did not
engage a site safety supervisor
as required by regulation.
Root Cause Analysis
Evaluation of loss
Type of contact
Immediate cause(s)
Basic cause(s)
Failure of SMS
• One worker killed and one injured
• Struck by object
• Improper placement
• Failure to secure
• Inadequate leadership and/or supervision
• Lack of experience
• Inadequate work standards
• Hazard analysis and risk assessment
• WSH practices and procedures
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Follow-up
A Stop Work Order (SWO) was issued to the main contractor which
required them to put in place a safety organisational structure and
management system to better manage the project as well as rectify
the unsafe site condition.
The SWO also required the project management staff of the main
contractor to attend a safety training workshop organised by OSHD.
Workers of the worksite were also required to attend the “Safety
Orientation Course for Construction Workers” conducted by OSHD.
This was to increase their awareness and knowledge about site
safety.
Recommendations
Conduct risk assessment prior to job commencement.
Stack materials properly so as to prevent materials from falling and
practice good housekeeping to prevent accidents.
Do not conduct multiple hazardous activities at the same time or
in the same place. In this case, heavy materials were stored near
a deep excavation.
72 Struck By Falling Objects
• It was also found that the boom
hoist wire rope was not of the type
that the manufacturer had specified.

CASE 4
STRUCK BY STEEL BEAMS
Description of Accident
Two workers were standing on the
deck of a lorry to unload steel
beams. The lorry which was
unmanned and parked on a slope,
rolled down the slope.
The steel beams swung off the
moving lorry and hit the workers.
One worker died while the other
suffered some cuts.
Causes and Contributing
Factors
• The lorry loader driver had
switched off the engine and
engaged the hand brake
of the lorry. However, he did
not place stoppers behind
the wheels of the lorry which
would have prevented the
lorry from rolling down
the slope.
1. Crawler crane
2. Lorry involved in the accident
3. Slope
4. Steel beams
5. The deceased
1. Crawler crane
2. Lorry
3. Steel beams
• The slope was cut at a gradient of
one to seven which is considered
steep for a workplace. Despite its
steepness, the occupier did not
impose the necessary safety
precautions before allowing lifting
operations to be carried out.
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Root Cause Analysis
Evaluation of loss
Type of contact
Immediate cause(s)
Basic cause(s)
Failure of SMS
• One worker killed and one injured
• Struck by object
• Failure to secure
• Lack of experience
• Inadequate work standards
• Hazard analysis and risk assessment
• WSH practices and procedures
Follow-up
The occupier reviewed and improved the lifting operations on
the slope area.
The lifting personnel were instructed that no lifting operation is
to be carried out on the slope area.
If lifting operations are to be carried out on the slope area due to
an unavoidable situation, the following precautions are to be taken:
• To reduce the amount of load to be unladed onto the lorry.
• The lorry driver is to place stoppers to prevent the lorry from
sliding down the slope.
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Recommendations
Place stoppers behind the wheels of the lorry before any loading
and unloading.
Provide regular safety briefings to drivers on loading and
unloading procedures.
Take extra care to ensure the safety of personnel working near
crane operations.
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CASE 5
STRUCK BY FALLING MATERIAL IN A TRENCH
Description of Accident
Worker A was supervising the
excavation of a trench. The bank
of the trench collapsed and Worker
A was found inside the trench,
partially covered with the granite
rocks and quarry dust that slid
from the bank. He had suffered
severe head injury and was
pronounced dead at the scene.
Causes and Contributing
Factors
• Prior to the accident, the project
manager checked the excavation
work and saw that the depth
of the trench had not met
requirements.
1. The deceased was found here
2. The “changkol”
3. The crow-bar
4. The collapsed quarry dust and
granite rocks
5. The tarmac
6. The granite rocks
7. The quarry dust
• He told Worker A to install
shoring for the trench before
further excavation.
• Worker A then tasked two other
workers to carry out shoring
work for the trench.
• While the workers went to fetch
the timbers, Worker A was seen
going into the trench to check
for any underground services
that might be located near the
1. The new substation
2. The excavator used for excavating
the trench
3. The timbers to be used for shoring
4. The trench was located here
76 Struck By Falling Objects

trench. This was to ensure the
services would not be damaged
when the timbers (shoring
support) were inserted into
the ground.
• The trench collapsed and
granite rocks and quarry dust
landed on Worker A.
Root Cause Analysis
Evaluation of loss
Type of contact
Immediate cause(s)
Basic cause(s)
Failure of SMS
• One worker killed
• Struck by object
• Inadequate guards or barriers
• Inadequate work standards
• Lack of experience
• Hazard analysis and risk assessment
• WSH practices and procedures
Follow-up
A Stop Work Order was issued.
Recommendations
Provide shoring prior to allowing entry into an excavation.
Conduct risk assessment of hazards prior to work commencement.
Conduct regular safety briefings/tool box meetings before entry
into an excavation.
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CASE 6
STRUCK BY A CRANE BOOM
Description of Accident
A crane operator was operating
a crawler crane to install a pre-cast
staircase. He hoisted the pre-cast
staircase from the ground to a
height just above the building
that was still under construction.
As his view of the unloading
was partially obstructed by the
building column, he inched the
crane forward causing the crane
to tilt forward and collapse.
1. The pre-cast staircase
The crane operator was trapped in
the cabin but subsequently freed
himself with the help of other
workers.
A worker who was working at
about 33m away from the crane,
was hit by the boom when the
crane collapsed.
Causes and Contributing
Factors
1. Location where the deceased was hit
by the falling boom
2. The second piece of the pre-cast staircase
• When the crane operator’s vision
was partially obstructed, he did
not wait for the signalman to
get to the top of the building
to give him further instructions
78 Struck By Falling Objects

and proceeded to move the
crane forward with the
suspended load in order to
obtain an unobstructed view
of the unloading position.
This was not a safe practice.
• Investigations concluded that
the collapse of the crane was
due to the crane moving
beyond the steel plates which
caused the crane’s crawler
“track” to dip into the ground
and tilt to an extent that the
crane was unstable.
• Investigations also revealed
that the maximum safe working
load of the collapsed crane
(i.e. 5880kg) as certified by
the approved person was
exceeded. The pre-cast
staircase weighed 7200kg.
Root Cause Analysis
Evaluation of loss
Type of contact
Immediate cause(s)
Basic cause(s)
Failure of SMS
• One worker killed
• Caught between or under object (crushed)
• Improper lifting
• Improper attempt to save time
• WSH practices and procedures
Follow-up
The occupier was instructed not to exceed the maximum safe
working load as verified by the approved person (authorised
examiner) when operating the lifting machines (cranes).
The occupier was also instructed to review and enhance the Safety
Management System (SMS).
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Recommendations
Check the crane base/foundation prior to lifting.
Conduct proper risk assessment to ensure that the risk exposure is
reduced to as low as reasonably practicable.
Crane operators should not take ad-hoc decisions without
assessing the overall situation.
Ensure continuous supervision for all lifting operations.
80 Struck By Falling Objects

CASE 7
HIT BY A COLLAPSED WALL
Description of Accident
A worker was demolishing a
partition brick wall inside a toilet
at the third floor of a building.
He was hit by a wall that collapsed
on him. He was subsequently
sent to hospital where he passed
away on the same day.
Causes and Contributing
Factors
1. The 10-pound hammer that was used
for the hacking operation
• Investigations revealed that the
worker had hacked the partition
wall from the bottom section
using a 10-pound hammer.
The collapsed wall weighed
about 300kg.
• The partition wall was simply
resting on the ground and
abutted against the adjacent
main wall. There was no
interlocking joint between
the partition wall and the
main wall.
• Hacking of walls should start
from the top section and should
be extended down progressively
so as to maintain its stability.
1. Partition wall that had collapsed and
hit the deceased on the head
2. The concrete breaker that was used
for removing the wall tiles
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In this case, a wrong sequence of
demolishing the partition wall
was employed (i.e. from bottom
section first).
• Coupled with the weak design
of the partition wall, it resulted
in the structural collapse of
the wall.
Root Cause Analysis
Evaluation of loss
Type of contact
Immediate cause(s)
Basic cause(s)
Failure of SMS
• One worker killed
• Caught between or under object (crushed)
• Improper position for task
• Lack of knowledge
• WSH practices and procedures
Follow-up
The occupier was instructed to undertake the following
improvements to the work practices/conditions at the site:
• Prior to demolition work, the supervisor should check the
site and brief the workers properly to ensure that they fully
understand the safe work procedures and sequencing of work.
Interpretation from native workers should be employed
when necessary.
• Workers should be grouped into teams of two or more when
carrying out demolition work.
82 Struck By Falling Objects

Recommendations
Provide proper design and shoring of the wall.
Follow proper sequence of demolition.
Provide supervision during demolition to ensure that the worker
works safely.
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83

CASE 8
HIT BY STEEL REBARS
Description of Accident
A lorry driver had delivered two
bundles of rebars to a worksite.
Two other workers assisted him in
the unloading of rebars.
While the lorry driver and other
workers were unloading a bundle
of steel rebars from the lorry using
the lorry crane, the bundle of
rebars fell onto the lorry driver.
1. Rebars bundles
Causes and Contributing
Factors
• The rebars measured 12m long
and 10mm in diameter.
• One end of the bundle of rebars
was lifted from the lorry and
placed on the ground.
• The other end of the same
bundle, which was placed on
the top of a bracket above the
front of the lorry, slid down
from the lorry and hit the lorry
driver who was operating the
lorry crane at the time of
accident.
1. The deceased was operating the
lorry crane in this position
84 Struck By Falling Objects

• Site investigations indicated
that the boom length of the
crane was about 7.5m in which
the recommended safe
working load was about
1730kg. However, the weight
of the bundle of rebars was
more than 2000kg. Hence
the workers had to lift the
bundle of rebars at one end
as the lorry crane could not
withstand the full load of
the bundle.
• The lorry driver and the two
workers had not undergone
any training course in rigging
operations. The lifting
supervisor was also not
informed of the lifting activity.
Root Cause Analysis
Evaluation of loss
Type of contact
Immediate cause(s)
Basic cause(s)
Failure of SMS
• One worker killed
• Struck by moving object
• Improper lifting
• Lack of knowledge
• Lack of skill
• Inadequate supervision
• WSH training and competence
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Follow-up
The occupier was instructed to undertake the following
improvements to the work practices/conditions at the site:
• To review their lifting procedures and improve the communication
channels between the lifting supervisor and the trade foremen.
• To increase the manpower stationed at the entrance of the
worksite to ensure that the cranes coming into their worksites
are properly attended to.
Recommendations
Ensure that the capacity of crane is greater than the load to
be lifted.
Closely supervise a lifting operation.
Improve lifting procedures and ensure that it is communicated to
all lifting personnel.
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CASE 9
BURIED UNDER COLLAPSED SOIL
Description of Accident
Worker A and his co-workers
were working inside an excavation
in a multistorey carpark. Worker A
was trimming the side of the
excavation when the soil suddenly
collapsed and pinned him down
up to his chest level.
Worker A was rescued from
the collapsed soil and sent to
the hospital where he
subsequently passed away.
1. Collapsed soil
2. Timber planks
3. Ladder
Causes and Contributing
Factors
• The depth of the excavation
measured 2.9m.
• The sides of the excavation
were almost 90°. They were
not shored. The adjacent
excavations were also not even
partially shored.
1. Shovel
2. Timber planks
3. The deceased was found underneath
this chunk of soil
4. Pile heads
5. Lean concrete
• The senior resident engineer of
the worksite confirmed that
hacking and placing of lean
concrete work were carried out
inside the excavation before it
was shored.
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• The operator of the excavator
confirmed that hacking work to
the pile-caps was carried out by
a breaker deployed at the edge
of the excavation before it
was shored.
• The accident occurred because
the factory occupier did not
provide shoring to the
excavation before allowing
the workers to work there.
Root Cause Analysis
Evaluation of loss
Type of contact
Immediate cause(s)
Basic cause(s)
Failure of SMS
• One worker killed
• Caught between or under (crushed)
• Inadequate guards or barriers
• Inadequate work standards
• WSH practices and procedures
Follow-up
The occupier was instructed to submit safe work procedures for
all excavation work on site and ensure that all workers follow the
safe practices.
88 Struck By Falling Objects

Recommendations
Provide shoring prior to any work in an excavation exceeding 1.5m.
Provide close supervision for any work in an excavation.
Conduct regular checks on excavation side stability.
Struck By Falling Objects
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CASE 10
CRUSHED BY A COLLAPSING BOOM
Description of Accident
A crawler crane mounted on a
crane barge was lifting two crates
of acetylene and oxygen cylinders
over to a jetty mooring dolphin.
After the crane boom had swung
over to the dolphin, the crane
suddenly vibrated violently.
The next moment, the crane
boom came crashing down.
A worker was crushed by the
collapsing boom and died on
the spot. Another worker
suffered leg injury caused by
the falling crates of acetylene
and oxygen cylinders.
1. View of the dolphin and the Emergency
Safety Access
Overview of collapsed crane
Causes and Contributing
Factors
• Investigations revealed that
the boom hoist wire that was
supporting the boom had
snapped, thus causing the
crane boom to collapse on
the workers.
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• The cause of the accident was
most probably due to the poor
maintenance of the boom
hoist wire rope. Excessive
wear/abrasion on the wire
rope surfaces might have
resulted in the sudden fracture
of the boom hoist wire.
• The boom wire rope used on
the crane involved in the
accident was of inadequate
strength. The wire rope used
had a breaking strength of
37 tons but according to the
manufacturer’s specification,
it should be 41.9 tons.
Root Cause Analysis
Evaluation of loss
Type of contact
Immediate cause(s)
Basic cause(s)
Failure of SMS
• One worker killed
• Struck by falling object
• Defective tools, equipment or materials
• Inadequate maintenance
• WSH practices and procedures
• WSH inspection
Recommendations
Ensure planned maintenance.
Ensure regular inspection.
Ensure the hoist wire of the crane is sufficiently strong with
an appropriate factor of safety.
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CASE 11
STRUCK BY FALLING TIMBER
Description of Accident
Worker A and his co-worker were
to dismantle formwork for the wet
joint at a lift lobby of a lift shaft,
from the seventh to 12th storey.
Worker A had loosened a
horizontal prop that was used to
secure two timber formwork
pieces on both sides of the wall
of the nineth storey lift lobby.
The timber piece on one side fell
into the lift shaft opening and
struck Worker A who was clearing
debris at the bottom of the lift
shaft. Worker A suffered serious
head injuries and succumbed to
his injuries on the same day.
1. The new lift shaft under construction
Causes and Contributing
Factors
• The timber formwork for the wet
joint at the nineth storey‘s lift
shaft lobby was supported and
held in position by two horizontal
and two vertical metal props.
1. This timber fell into the lift shaft
opening
2. The lift shaft opening
3. The timber formwork for the
wet joint
4. The plywood fencing was put up
after the accident
5. The position of the lower
horizontal prop
6. Deceased was squatting here when
loosening the horizontal metal prop
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• Prior to the accident, one worker
had removed the two vertical
props and the higher of the
two horizontal props. The
timber piece on one side fell
into the lift shaft opening after
he had loosened the lower
horizontal prop, which was
the last prop holding the timber
formwork in position.
• At the time of the accident
the lift shaft opening was not
fenced or covered with any
plywood or other material.
The falling timber fell into
the lift shaft opening and
struck Worker A who was
clearing debris at the bottom
of the lift shaft.
Root Cause Analysis
Evaluation of loss
Type of contact
Immediate cause(s)
Basic cause(s)
Failure of SMS
• One worker killed
• Struck by falling object
• Inadequate guards or barriers
• Inadequate work standards
• Inadequate leadership and/or supervision
• Hazard analysis and risk management
• WSH practices and procedures
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Follow-up
The occupier was instructed to implement the following safety
measures:
• The foreman-in-charge is to check and ensure that lift shaft
openings are securely fenced with timber prior to assigning
workers to dismantle formwork at the lift lobby.
• No worker is to be assigned to work in the lift pit if any work is
carried out above.
• Workers assigned to dismantle formwork are to be instructed to
check for the presence of the fencing of the lift shaft openings
prior to the commencement of work. They should stop work
and report to their supervisor if the lift shaft opening is not
securely barricaded.
Recommendations
Ensure proper supervision.
Ensure that incompatible work is not carried out simultaneously
at a particular location.
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CASE 12
STRUCK BY A FALLING CRANE BOOM
Description of Accident
A crawler crane operated by a
worker was lifting a bundle of
rebars from the ground floor to the
second storey of an uncompleted
building.
When the bundle of rebars was
about to be unloaded, the crane
boom suddenly collapsed.
Two workers were killed and
another injured as a result of the
collapsed boom.
1. Rebars bundle
2. Main hook block
3. One of the deceased was hit and pinned
under the fly jib here
4. Auxiliary hook block
Causes and Contributing
Factors
• Investigations revealed that the
boom hoist wire rope that was
supporting the boom had
snapped, causing the crane boom
to collapse onto the workers.
• Laboratory findings indicated
that the wire rope had failed
as a result of accelerated fatigue.
This means that the failure had
occurred in the internal areas of
the wire rope which are hard
to detect during a routine
visual inspection.
1. Gantry bridle
2. Boom hoist wire rope
3. A completely broken portion (about
2.5m) of the boom hoist wire rope
found on the ground
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• It was also found that the boom
hoist wire rope was not of
the type that the manufacturer
had specified. The breaking
strength of the wire rope was
also lower than what the
manufacturer had specified.
• The crane operator did not
know how to read and interpret
the load capacity chart.
Root Cause Analysis
Evaluation of loss
Type of contact
Immediate cause(s)
Basic cause(s)
Failure of SMS
• Two workers killed
• Struck by crane boom
• Defective tools, equipment or materials
• Inadequate removal and replacement of
unsuitable items
• Inadequate maintenance
• Maintenance regime
Recommendations
Ensure that the wire rope used is the type specified by manufacturer.
Conduct regular checks before lifting operations.
Continually train the crane operator on how to read and interpret
the load capacity chart.
Ensure that the lifting supervisor is present for all lifting operations.
96 Struck By Falling Objects

CASE 13
STRUCK BY A COLLAPSED WALL
Description of Accident
Worker A and his co-worker were
working in a trench at the worksite.
They were laying and tightening
reinforced steel wires at the
bottom of the trench.
The boundary wall of the adjacent
house that was standing at the
edge of the trench toppled into
the trench. Worker A was pinned
under the collapsed wall.
1. The boundary wall was here before
it toppled
2. The deceased was pinned here under
the wall
3. The trench
Causes and Contributing
Factors
• The boundary wall that toppled
measured about 15.5cm in
thickness, 160cm in height and
1680cm in length. It was a brick
wall with plaster on its surface.
• The trench where Worker A and
his co-worker worked was dug
parallel to this boundary wall.
• No support such as sheet piling,
bracing, shoring, underpinning
or other means to ensure the
stability of the boundary wall
beside the trench had been put
up to prevent injury to workers
working in the trench.
1. The deceased was pinned here under
the wall
Struck By Falling Objects
97

• Excavation of the trench had
weakened the foundation of the
boundary wall. As some of the
earth below the cement slab on
which the boundary wall was
erected had fallen off into the
trench, the cement slab’s
strength to support the
boundary wall was reduced.
• The cement slab gave way and
resulted in the wall toppling into
the trench.
Root Cause Analysis
Evaluation of loss
Type of contact
Immediate cause(s)
Basic cause(s)
Failure of SMS
• One worker killed
• Struck by object
• Failure to secure
• Inadequate work standards
• Hazard analysis and risk assessment
Follow-up
The occupier was instructed to erect supports according to the
design of a professional engineer for structures adjoining any
trench to prevent injury to any person working in the trench.
Recommendations
Provide supports such as sheet piling, bracing, shoring, underpinning
or other means to ensure the stability of a boundary wall beside a
trench to prevent injury to workers working in the trench.
Ensure that the integrity of the wall is checked regularly by a
competent person.
98 Struck By Falling Objects

Published in June 2008 by the
Workplace Safety and Health
Council in collaboration with
the Ministry of Manpower.
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