Topic 3 Flashcards
The fatality rate for excavation work is ___ higher than the rate for geenral construction.
112%
OSHA reports ___ trench deaths in 2022 - more than double 2021 toll
39
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 that 15 ft
Trench Excavation
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
Soil
Soil Types
Stable Rock
Type A
Type B
Type C
Natural solid mineral matters
Stable Rock
Cohesive soil with unconfined compressive strength of 1.5 tons per square foot or greater
Type A
Cohesive soil with strength greater than 0.5 tsf but less than 1.5 tsf
Type B
Cohesive soil strength 0.5 tsf or less
Type C
pose the greatest risk to workers’ lives
Trench collapses, or cave-ins
Trenches 5 feet (1.5 meters) deep or greater require a ______ unless the excavation is made entirely in stable rock
protective system
Trenches 20 feet (6.1 meters) deep or greater require that the protective system be designed by a _________ or be based on tabulated data prepared and/or approved by a _________ in accordance with 1926.652(B) and (C)
registered professional engineer
is an individual who is capable of identifying existing and predictable hazards or working conditions that are hazardous, unsanitary, or dangerous to workers
competent person
Keep heavy equipment away from ______
trench edges
keep excavated soil (spoils) and other materials at least ______ from trench edges
2 feet (0.6 meters)
know where underground utilities are located before ___
digging
test for atmospheric hazards such as low oxygen, hazardous fumes and toxic gases when ___deep
> 4 feet
inspect trenches following a ___ or other water intrusion
rainstorm
do not work under ___ or raised loads and materials
suspended
ensure that personnel wear ______ or other suitable clothing when exposed to vehicular traffic
high visibility
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
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
Shielding
means loosening and taking out materials leaving space above or below ground
Excavation
Advantages of using the Mechanical Plant in Excavation
Work Done Quicker
Avoid the Dangerous Condition of Work by Human Workers
Achieve Greater Depth
Use Fewer Manpower and Work Done at Lower Cost
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
Berms
___ posted to prevent the public from going near the excavation
Signs
Walkways or bridges has minimum clear width of ___
20 in
Walkways or bridges has an extended a minimum of ___ past the surface edges
24 in
Excavation shall be kept free of ___ at all times
water
In muddy areas, workers should be provided with ___ to reduce the hazard of slipping
boots
Determine location of underground ____ and take necessary steps to prevent damage
facilities
2 Major Methods for Controlling Ground Water
Pumping Technique
Exclusion Technique
Oxygen Deficient Atmosphere
less than 19.5% oxygen
___ from decayed matter
methane
Shoring or timbering in excavation over ___ deep shall be designed by a structural engineer and approved by the proper authority
6.6 m
No excavation in an ___ building or structure shall be undertaken unless steps are taken to prevent danger to worker
adjacent
Before shoring or timbering, the walls of an excavation shall be stripped of ______ or other materials that might slide or fall on workers
loose rocks
Keep excavated material from the edge of the excavation to provide a clear berm not less than the _________
third of the depth of excavation
Tools, materials, and machinery keep at least ___ away from the edge of the excavation
1m
The top of the walls of an excavation more than ____ deep shall be barricaded to a height of at least ___
2m, 1m
Every excavation shall have at least one ___ in every ___ of length which shall extend at 0.83 above the top
ladder, 16.6 m
Every part of an excavation over 2m deep where workers work shall be inspected by the person in charge at least ___ everyday
once
use of ______ or other means to free the area of such contaminants
exhaust ventilation
