Trench Collapse

Question 1

What are the 6 features of a trench?

Answer 1

1. Spoil pile
2. Walls
3. Belly
4. Floor
5. Toe
6. Lip

Question 2

What are the factors influencing trench collapse?

Answer 2

BATSWAC

1. Buried obstructions (manholes, tree roots)
2. Angle and height of sides
3. Type of soil
4. Sand or previously disturbed ground
5. Water in ground or on surface
6. Adjacent loads (spoil piles, vehicles)
7. Climatic conditions (rainfall, thawing ground)

Question 3

What are four signs of trench collapse?

Answer 3

1. Tension cracks
2. Sliding
3. Subsidence and bulging
4. Layered soil failure
5. Wedge failure
6. Rotation failure
7. Sloughing
8. Soft pockets
9. Soft zone failure

Question 4

What are the four main incidents involving trenches?

Answer 4

1. Becoming trapped or buried below ground level
2. Being crushed by movement of soil or equipment
3. Falling into open trenches or pits
4. Drowning or being overcome by fumes

Question 5

What are the hazards involved with trench incidents?

Answer 5

1. Restricted access and working area
2. Utilities
3. Plant and machinery
4. Ingress of water and mud
5. Biohazards
6. Poor lighting conditions

Question 6

What distance should vehicles be from a trench?

Answer 6

At least 15m

Question 7

What are the three zones for trench incidents?

Answer 7

1. Hot zone- 15m
2. Warm zone- 45m
3. Cold zone- 90m

Question 8

What are the three USAR safe systems of work for trench collapse incidents?

Answer 8

1. Sloping
2. Shielding
3. Shoring

Question 9

What should be used to spread the load outside a trench?

Answer 9

Ground pads

Question 10

What are other considerations of trench incidents?

Answer 10

1. Ground pads
2. Means of escape
3. Ventilation
4. Shoring
5. Zones