Date post: | 16-Dec-2015 |
Category: |
Documents |
Upload: | shreya-tyrell |
View: | 217 times |
Download: | 0 times |
2
Excavation Safety
Introduction
In order to prevent injuries and improve work productivity, APS has developed this training to provide you the knowledge to stay safe when working in and around excavations.
3
Excavation Safety
Introduction About 400 U.S. workers die in trench-related
accidents each year
About 6,400 are seriously injured
For this reason it is important to understand how to stay safe in and around excavations
4
Excavation Safety
Introduction
In this training we will cover:
What is a trench? Soil characteristics Collapse types Shoring techniques Safety requirements
5
Excavation Safety
What is a Trench?
A narrow excavationthat is deeper than it is wide
No more than 15 feet wide at bottom
Walls will eventually fail
6
Excavation Safety
What is a Trench?
Failure of trench walls results in cave-in:
Soil or rock that suddenly falls or slides into an excavation
Sufficient quantity to entrap, bury, injure, or immobilize Soil gravitates downward, pressure pushes soil inward
toward the trench Bottom third of wall typically fails first Soil above the collapsed lower wall follows
7
Excavation Safety
What is a Trench?
Cave-ins are dangerous to workers:
Soil weighs 125 lbs. per cubic foot A worker can be crushed by soil, rock, or an object Suffocation—even if worker’s head is not buried, soil
prevents chest expansion Worker becomes immobilized by soil’s suction effect
8
Excavation Safety
Soil Characteristics
Type A (most stable) — dense and heavy clay
Type B — silt, sandy loam, medium clay
Type C (least stable) — gravel, loamy sand, soft clay
9
Excavation Safety
Soil Characteristics
Factors affecting soil strength: Water Vibrations Erosion and Weathering Excavation Depth Slope Steepness Degree of Soil Compaction
10
Excavation Safety
Soil Characteristics
Signs of impending collapse:
Fissures or cracks on excavation face Slumping of material from excavation face Bulging or heaving of material at the bottom of
excavation wall Sinking of excavation’s edge Ravelling, or small amounts of material (e.g.,
pebbles) trickling into excavation
11
Excavation Safety
Collapse Types
There are four types of trench collapses:
Spoil Pile Slide
Side Wall Shear
Slough–in
Rotation
12
Excavation Safety
Collapse Types
Spoil Pile Slide -Collapse of material that hasbeen removed from the trench back into the trench
15
Excavation Safety
Collapse Types
Rotation -Collapse of bottom thirdof trench wall causingsecondary wall collapse
16
Excavation Safety
Shoring Techniques
Engineers are often required to design shoring, which is a construction procedure used specifically to maintain the stability of the walls of an excavation and provide protection to workers who may enter the excavation
17
Excavation Safety
Shoring Techniques
To mitigate the danger of cave-ins, there are 4 main techniquesto shore trench walls:
Wood Support
Screw Jacks
Hydraulic Shores
Trench Cages
22
Excavation Safety
Safety Requirements
At least one worker in each work crew must be experienced in the type of work being performed in excavations
At least one worker should be trained in first aid
23
Excavation Safety
Safety Requirements
Protecting the area around the excavation:
All work areas must be adequately guarded or barricaded by fences, guardrails or a covering sufficient to prevent persons from falling into the excavation
Excavations might endanger stability of buildings, walls, other structures
Sidewalks, pavement not undermined unless supported to prevent collapse on excavation workers
24
Excavation Safety
Safety Requirements
Protecting workers in excavations:
Protect workers from loose rock/soil that may fall from an excavation face
• Use scaling to remove loose soil• Use protective barricades, such as shoring or shields
Protect workers from material or equipment that could fall into the excavation
• Keep material/equipment at least 3 feet from edge
• Use retaining devices
25
Excavation Safety
Safety Requirements
Protecting workers in excavations:
Excavation sites cannot be covered with anything such as piles of excavated material or excavation equipment which might accidentally fall into the excavation
26
Excavation Safety
Safety Requirements
Protecting workers in excavations:
Trenches 4 feet deep or more must have exit means within 25 feet of every worker
Use fall protection Do not work on sides of sloped or benched
excavation above other workers For parallel construction have a worker on top to
watch excavation walls to warn trench workers of potential hazards
27
Excavation Safety
You are finished!
You have finished the Excavation Safety training.
Download the quiz from the Risk Management website’s training page.
Print the form and be sure to write your name, location and employee number in the spaces provided.
Complete the ten questions and have your supervisor send it to the Risk Management office