Trench Rescue

Question 1

Trench and trench collapse rescue may be required as a result of

Answer 1

Collapse of trench walls.
Workers suffering injury or illness in the trench.
Workers trapped/ injured by machinery or pipes falling into trench.

Question 2

How is a trench defined

Answer 2

A trench is defined as a long excavated channel, more than 1.5m deep and longer than they are wide or deep. Legal requirements state that any trench deeper than 1.5m must be shored.

Question 3

Is secondary collapse likely

Answer 3

Yes its important to be aware that in 50% of trench collapse incidents secondary collapse is likely to occur.

Question 4

Signs of impending trench collapse

Answer 4

Parallel cracks.
Fretting.
Slumping.
Bulging Walls.
Deflection and creaking of shoring.

Question 5

Types of trench collapse

Answer 5

Single or both sides possible.
Lip collapse. Top section falling.
Sloughs. Undercut trench.
Shearing. Sections of entire wall falling.
Soil piles sliding into trench.

Question 6

Causes of trench collapse

Answer 6

Ground pressure.
Adjacent excavation.
Unstable ground.
Clay.
Loose rocks.
Water.
Loading.
The spoil pile.
Vibration.
Insufficient shoring.
Movement of ground support system.

Question 7

Max depth of use for Verti-shore system

Answer 7

5m

Question 8

Verti-shore installation

Answer 8

Installed at 1200mm centres.
As close to plumb and level as possible.
Install top down and remove bottom up.
Position top piston between 300 - 600mm from the top.
Bottom piston should be max 1200mm from the bottom.
Pressurise to the point of holding, not moving.

Question 9

Ground support system components

Answer 9

Hydraulic rescue shores.
Extension tubes.
Hydraulic hand pump.
Release tools.
Plywood sheeting.

Question 10

Points to remember

Answer 10

All installation and removal of the verti-shores must be done from the top of the excavation.
Rescuers working in a trench must remain inside the rescue shores at all times.
At no stage should a person enter an unshored or inadequately shored trench to perform rescue.
Do not use shoring as a ladder.

Question 11

Describe angle of repose

Answer 11

The natural angle loose soil assumes one piles up.

generally become the battering back angle.

Question 12

Questions to ask on trench rescue arrival.

Answer 12

What has happened?
How many victims are there?
Where in the trench were they last seen?
How deep is the trench?
What is the purpose of the trench?
What has been done so far?

Question 13

How to locate a potential trench rescue casualty

Answer 13

Position of tools or clothing such a jumpers.
Materials are usually laid out on the side of the trench -The point of where materials have been used up until.
Surveyors staff.
Sound of voices coming from large diameter pipe.
Tyre tracks from last point excavator was.

Question 14

How to extricate trench rescue casualty

Answer 14

Treat life-threatening injuries.
Carefully uncover dirt, ensuring not to hit casualty with shovel. Use short handle shovels in scraping motion.
Never attempt to pull the casualty out until they are completely uncovered.
Transfer casualty to stokes litter or spine board.
Once tied in, haul up a ladder with haul line and haul team.

Question 15

How to set up to work around a trench

Answer 15

Set up 100x100 blocks 1m back to transfer load away from the edge.
Position bearers across the blocks.
Position 145x45 planks across bearers to create walking space. Leave a gap between to allow visibility below to check for signs of trench collapse.