TOPIC 5: Excavation Safety Flashcards
THE FATALITY RATE FOR EXCAVATION WORK IS ____ THAN THE RATE FOR GENERAL CONSTRUCTION.
112% HIGHER
OSHA Reports ____ in 2022 Than Double 2021 Toll - More
39 Trench Deaths
Eliminate hazards and control risks by implementing precautions in excavations and trenches with:
- Pre-planning
- Protective systems
- Safety measures
- Inspections
*IS ANY MAN-MADE CUT, CAVITY OR DEPRESSION IN AN EARTH SURFACE THAT IS FORMED BY EARTH REMOVAL
EXCAVATION
*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 ____
TRENCH EXCAVATION; 15 FT.
HAZARDS OF EXCAVATION WORKS
*SOIL COLLAPSE
*FALLING OBJECTS *UNDERGROUND UTILITIES *WORKING SURFACES
*CONFINED SPACE CONDITIONS
Types of Soil Collapse
- Sliding
- Bulge
- Toppling
- Boiling
- Heave
PRINCIPAL CAUSES OF SOIL COLLAPSE
- STEEP CUTTING ANGLE
- SUPER IMPOSED LOAD
- SHOCK AND VIBRATION
- WATER PRESSURE
- DRYING
IS A MIXTURE OF ROCK, WATER, AIR AND A VARIETY OF OTHER SUBSTANCES
- A SOIL
- SOIL IS MADE UP OF ROCK IN THE FORM OF SMALL PARTICLES AND SPACES CALLED ____. NORMALLY SOME PART OF THESE ARE FILLED WITH WATER
VOIDS
Description: Natural solid mineral matters
Examples: Rock, hilly terrain
Subtle rock
Description: Cohesive soil with unconfined compressive strength of 1.5 tons per square foot or greater
Examples: Clay, silt, sandy clay
Type A
Description: Cohesive soil with strength greater than 0.5 tsf but less than 1.5 tsf
Examples: Angular gravel (similar to crushed rock)
Type B
Description: Cohesive soil strength 0.5 tsf or less
Examples: Granular soil such as grave, sand and loamy sand
Type C
MECHANICS OF A CAVE-IN:
trench collapses, or cave-ins, pose the greatest risk to workers’ lives. when done safely, trenching operations can reduce worker exposure to other potential hazards including falls, falling loads, hazardous atmospheres, and incidents involving mobile equipment.
*TRENCHING AND EXCAVATION SAFETY
TRENCH SAFETY MEASURES
trenches ______ require a protective system unless the excavation is made entirely in stable rock. if less than 5 feet deep, a competent person may determine that a protective system is not required.
5 feet (1.5 meters) deep or greater
TRENCH SAFETY MEASURES
trenches ____ require that the system be designed by a protective registered professional engineer or be based on tabulated data prepared and/or approved by a registered professional engineer in accordance with _____.
20 feet (6.1 meters) deep or greater; 1926.652(b) and (c)
osha standards require, before any worker entry, that employers have a _____ inspect trenches daily and as conditions change to ensure the elimination of excavation hazards.
*COMPETENT PERSON
is an individual who is capable of identifying existing and predictable hazards or working conditions that are hazardous, unsanitary, or dangerous to workers, soil types, and protective systems required, and who is authorized to take prompt corrective measures to eliminate these hazards and conditions.
COMPETENT PERSON
ACCESS AND EGRESS:
* keep heavy equipment away from ____.
trench edges
ACCESS AND EGRESS:
* identify other sources that might affect ___
trench stability.
ACCESS AND EGRESS
* keep ____ and other materials at least ____ from trench edges.
excavated soil (spoils); 2 feet (0.6 meters)
ACCESS AND EGRESS:
* know where ____are located before digging.
underground utilities
ACCESS AND EGRESS:
* test for atmospheric hazards such as low oxygen, hazardous fumes and toxic gases when ____ inspect trenches at the start of each shift.
> 4 feet deep.
ACCESS AND EGRESS:
* inspect trenches following a _____
rainstorm or other water intrusion.
ACCESS AND EGRESS:
* do not work under ____
suspended or raised loads and materials.
ACCESS AND EGRESS:
* inspect ____ after any occurrence that could have changed conditions in the trench.
trenches
ACCESS AND EGRESS:
* ensure that personnel wear _____ when exposed to vehicular traffic.
high visibility or other suitable clothing
PROTECTIVE SYSTEMS THERE ARE DIFFERENT TYPES OF PROTECTIVE SYSTEMS.
- Benching
- Sloping
- Shoring
- Shielding
means a method of protecting workers 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. benching cannot be done in type c soil.
- benching
involves cutting back the trench wall at an angle inclined away from the excavation.
- sloping
requires installing aluminum hydraulic or other types of supports to prevent soil movement and cave-ins.
- shoring
protects workers by using trench boxes or other types of supports to prevent soil cave-ins. designing a protective system can
- shielding
Trenching Protection Methods
- Sloping
- Benching
- Shielding
- Shoring
be complex because you must consider many factors:
- soil classification,
- depth of cut,
- water content of soil, changes caused by weather or climate,
- surcharge loads (e.g., spoil, other materials to be used in the trench)
- and other operations in the vicinity.
mechanics of soil collapse in general, ____ means loosening and taking out materials leaving space above or below ground. sometimes in civil engineering term, ___is used which include backfilling with new or original materials to voids, spreading, and leveling over an area.
excavation; earthwork
EXCAVATION AND EARTHMOVING PLANTS ADVANTAGES OF USING THE MECHANICAL PLANT IN EXCAVATION:
a) work done quicker,
b) avoid the dangerous condition of work by human workers, say, the existence of groundwater or collapse of soil,
c) achieve greater depth,
d) use fewer manpower and work done at lower cost (for larger scale work only)
Stable Rock Vertical: Max slope and Slope Angle
90,-
Type A: Max slope and Slope Angle
3/4 : 1 ; 53
Type B: Max slope and Slope Angle
1:1 ; 45
Type C: Max slope and Slope Angle
1-1/2:1 ; 34
Prevention of Soil Collapse: Protective Sytem
- Provision of Shoring and Timbering
- Shoring for stable soil
- Shoring for loose soil
- Shoring for long trench
PREVENTION OF SOIL COLLAPSE: this involves digging the trench walls at an angle from the opening so that soil weight is away from the workers. the trench will have a funnel shape when its finished. its also important to make sure that the extra soil is placed 2m from the trench wall. this help prevent a trench collapse.
sloping
PREVENTION OF SOIL COLLAPSE: when metal plates are placed on either side of the trench. walls are kept in place with spacers matching the trench width or using a hydraulic system. hydraulics can provide constant even pressure on the walls to prevent trench collapse.
shoring
PREVENTION OF SOIL COLLAPSE even with the safety precautions of today’s modern construction firms, trench work has the potential to be extremely hazardous.
SHIELDING-BOXING
shielding uses all __ sides of the trench and that’s why a ___ is an excellent way to stabilize the trench and keep workers safe. depending on location and main purpose, these may also be known as ____ they can be permanent or portable as the trench work expands. they are made of steel or aluminium providing a strong framework to prevent trench collapse.
4 ; trench box ; sewer boxes, manhole boxes, trench shields, or tap boxes.
PREVENTION OF SOIL COLLAPSE * PROVIDE SAFE DISTANCE FROM 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 runoff.
BERM
PREVENTION FROM FALLING MATERIALS
- barricades should be provided
- signs posted to prevent the public from going near the excavation
PREVENTION OF FALL: SURFACE CROSSING OF TRENCHES
- 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
WORKING SURFACE Requirements
- excavation shall be kept free of water at all times
- in muddy areas, workers should be provided with boots to reduce the hazard of slipping
UNDERGROUND FACILITIES requirements
- determine location of underground facilities and take necessary steps to prevent damage to these facilities
GROUNDWATER CONTROL
_____ causes extreme geotechnical problems in excavations such as ____ for most of construction projects such as ____ . so, issues caused by ground water would increase construction budget and extend construction time unless the ground water is properly controlled which is the root cause of the problems. there are two major methods for controlling ground water including ____
groundwater ; sand running ; tunneling ; pumping technique and exclusion technique
CAN AN EXCAVATION BE A CONFINED SPACE…..?
* oxygen deficient atmosphere: less than ____
* potential for other gasses to be present include but not be limited to:
* ____ from potential leaks or cut lines
* ____ from decayed matter
19.5% oxygen ; natural gas; methane
- PROVISION OF SHORING AND TIMBERING
- excavation over 1m deep shall be supported by adequate _____ this shall not apply to such excavation
- a worker is not required to enter for any purpose cut in solid rock walls are sloped to ____ from the vertical or cut to the angle of repose
- shoring or timbering in excavation over ____deep shall be designed by a structural engineer and approved by the proper authority oshs rule ____: excavation
shoring and timbering. ; 45’; 6.6m ; 1413
OSHS RULE 1413: EXCAVATION
* no excavation in an ____ building or structure shall be undertaken unless steps are taken to prevent danger to worker
* before shoring or timbering, the walls of an excavation shall be _____ or other materials that might slide, roll or fall on workers
* every excavation over ___ shall be kept free of water at all times
adjacent ; stripped of loose rocks ; 1m
MINIMUM BERM
* keep excavated material from the edge of the excavation to provide a clear berm not less than ____ of excavation
* a berm of reduced width of not less than ___ may be allowed:
- materials being excavated are __
- shoring to carry the additional load barriers are provided to prevent ___ of the excavated material
- ___ are provided to prevent roll back of the excavated material
one third of the depth; 1m; stable ; roll back; Barriers
TOOLS, MATERIALS AND MACHINERY
* keep at least __ away from the edge of the excavation
* no vehicle or other machinery be driven, operated or located near the edge of an excavation at least __of its depth
1m; 1/3
PROVISION FOR BARRICADES
* the top of the walls of an excavation more than ___ deep shall be barricaded to a height of at least __
2m ; 1m
MEANS OF ACCESS AND ESCAPE
* every excavation over __ deep shall be provided with means of access and escape
* every excavation shall have at least one ladder in every __ of length which shall extend at __ above the top
1m; 16.6m; 0.83m
INSPECTION AND EXAMINATION OF EXCAVATION
* every part of an excavation over __ deep where workers work shall be inspected by the person in charge at least once everyday
2m
SUPERVISION AND EXECUTION OF TIMBERING AND OTHER WORK
* ___ only under direct supervision of project supervisor
* of good construction ___ and of adequate strength
* ___ be properly secured
* do not use timber giving off ___ or substance soluble in water
erected, added, altered or dismantled; sound materials; struts and bracings; toxic saps
HARMFUL DUST, GASSES AND FUMES
* Use ___ or other means to free the area of such contaminants
* operate ___ only of there is provision to discharge fumes from excavation
exhaust ventilation; internal combustion engine
SIZES AND SPACING OF MEMBERS
*-5CM X 15CM
SHEETING
SIZES AND SPACING OF MEMBERS
*10CM X 15CM
WALES
SIZES AND SPACING OF MEMBERS
* 10CM X 15CM
STRUTS
WORKING IN EXCAVATION
* PRIOR TO OPENING
* check ____
* protect all ___ installations
* remove _____ and hazards before starting excavation
excavation permit ; underground ; trees, boulders, stumps, other surface encumbrances
WORKING IN EXCAVATION
* DURING OPERATIONS
- wear ___
- store excavated materials at least ___ from edge
- remove boulders or other materials that may ___
- do not ___ materials or store equipment near edge or excavation
- give special attention to ___, adversely affected by weather, moisture content or vibration
goggles and hard hats ; 1m; roll ; stockpile ; side slops
WORKING IN EXCAVATION
* DURING OPERATIONS
✓ in case of ____, safely support overhanging materials
✓ ___ distance between workers ✓control ground water
✓ provide _______ for pedestrian/vehicular traffic
undercut; safe working; walkways, bridges, guardrails, barricades, warning flags or lights
EQUIPMENT OPERATIONS
* _____ sides of excavation to resist superimposed loads if necessary to operate equipment above or near excavation
* use _____ if mobile equipment is utilized adjacent to excavations
* do not work too close to the ____ of the excavation
* ____ to ensure safety working excavation
shore and brace ; stop logs, warning signs or barricades ; cliff or edge; use horn or give signals
WORKING IN EXCAVATION
* during break time, workmen should never stand or take rest on _____
* maintain guardrails, fences or other barricades and warning lights from____
* do not leave _____ in walkways, ramps or near the edge of excavation
* do not use ___ as resting place
high banks of soft material; sunset to sundown ; tools, materials or debris; guardrails
WORKING IN EXCAVATION
EXCAVATION IN CONFINED SPACE
* check the ____ before entry
* do not work ____in a confined space
* provide ____
* provide ___ before entering
* provide emergency rescue equipment such as _____
atmosphere condition; alone; life line; ventilation or blower ; breathing apparatus, safety harness and line and basket stretcher
INSPECTION
* ____ start of each shift
* after heavy rain
* when _____ at the bottom
* when there is a _____ of spoil pile
* when there is any ______ in adjacent structures
daily before; fissures, tension cracks, undercutting, water seepage, bulging; change in size, location, or placement ;indication of change or movement
