OSHA 10-Hour Construction ReviewExcavationsMedium
A trench shield (trench box) is being used in an excavation. What is the primary purpose of a trench shield?
- ATo prevent the trench walls from collapsing.
- BTo allow for steeper trench slopes than otherwise permitted.
- CTo protect workers inside the shield from a cave-in.
- DTo stabilize the surrounding ground and adjacent structures.
Show answer & explanationAnswer & explanation
Correct answer: C. To protect workers inside the shield from a cave-in.
The primary purpose of a trench shield is to protect workers who are inside it from the forces of a cave-in. Unlike shoring, a shield does not prevent the trench walls themselves from collapsing; instead, it provides a safe working space within a collapsing trench.
Why the other options are wrong
- A. This describes the primary function of shoring, not a trench shield. A shield protects workers from collapse, it doesn't prevent the collapse.
- B. Trench shields do not inherently allow for steeper slopes; the overall excavation design (including soil type and other factors) dictates the slope, and the shield protects inside it regardless.
- D. Stabilizing the surrounding ground is typically achieved through sloping or shoring, not primarily by a trench shield.
Trench Shield (Shielding)
A trench shield, or trench box, is a protective system that protects workers within the shield from cave-ins by creating a safe working space. It does not prevent the trench walls from collapsing.
- Protects workers from cave-ins.
- Does not prevent trench wall collapse.
- Provides a safe zone for workers.
- Must extend at least 18 inches above the excavation floor.
Memory trick: Shiels Save, Shores Support