OSHA 10-Hour Construction ReviewExcavationsHard
During a trenching operation, workers observe water seeping into the excavation and cracks forming on the trench sidewalls. Which type of protective system would be most effective in mitigating these immediate hazards and preventing a collapse?
- ASloping
- BBenching
- CShielding
- DShoring
Show answer & explanationAnswer & explanation
Correct answer: D. Shoring
Shoring is specifically designed to prevent cave-ins by supporting the excavation walls. The presence of water seepage and cracks indicates soil instability requiring active support, which shoring provides. Sloping and benching are less effective in active collapse situations, and shielding protects workers but doesn't prevent the collapse itself.
Why the other options are wrong
- A. Sloping reduces the angle of repose, but it's a preventative measure. Once cracks and water seepage are present, active support is needed.
- B. Benching modifies the excavation sides into a series of steps, but it does not actively support unstable soil or prevent collapse when cracks are already forming.
- C. Shielding (trench boxes) protects workers within the box but does not prevent the trench from collapsing around the box, nor does it stabilize the overall trench walls.
Shoring Systems
Shoring involves installing aluminum or steel hydraulic cylinders, or timber structures, to brace the sides of an excavation and prevent cave-ins.
- Provides active support to excavation walls.
- Prevents soil movement and collapse.
- Can be hydraulic, pneumatic, or timber.
- Used in unstable soil conditions or when space is limited.
Memory trick: Protect Every Trench Carefully