OSHA 10-Hour Construction ReviewExcavationsMedium
During an excavation inspection, a competent person observes signs of distress in the trench walls, including tension cracks several feet back from the edge and bulging at the bottom of the trench. Which type of protective system would be most appropriate to address these specific indicators of instability?
- ASloping the trench walls to a gentler angle.
- BUtilizing a shoring system with uprights, wales, and cross braces.
- CImplementing a benching system for the excavation.
- DInstalling a trench shield (trench box).
Show answer & explanationAnswer & explanation
Correct answer: B. Utilizing a shoring system with uprights, wales, and cross braces.
Tension cracks and bulging indicate an imminent or active cave-in. A shoring system, which provides active support to the trench walls, is designed to prevent such collapses by resisting the lateral pressure of the soil. Sloping or benching might be initial approaches but are insufficient once distress is evident, and a trench shield only protects workers inside, not the trench itself.
Why the other options are wrong
- A. Sloping is a preventative measure, but once distress is visible, active support is needed.
- C. Benching is a form of sloping and would not provide the active support needed to prevent an already distressed trench from collapsing.
- D. A trench shield protects workers from collapse but does not prevent the trench from collapsing. The question asks to address the instability of the trench walls.
Distress Indicators & Shoring
Visible signs of trench wall instability, such as tension cracks or bulging, necessitate immediate intervention, typically through the installation of an engineered shoring system.
- Tension cracks indicate potential failure at the top of the trench.
- Bulging indicates failure at the bottom due to soil pressure.
- Shoring provides active support to prevent collapse.
Memory trick: Cracks and Bulges? Time to SHORE up the problem!