In which case would "benching" be used for excavation safety?

Benching is a method used in excavation safety specifically designed to create a stable and safe work environment in excavations. This technique involves cutting back the trench walls at an angle, forming a series of steps or benches. This method is particularly effective in stable, cohesive soils because these types of soils have the ability to maintain their structure under certain conditions.

In cohesive soils, which are typically more densely packed and have better binding characteristics, the angled cuts can support the weight of the soil above the excavation, significantly reducing the risk of cave-ins. The benches help distribute the load of the soil and allow workers to safely access different levels of the excavation without needing extensive shoring or bracing systems, as long as the soil remains stable.

The other scenarios listed would not be suitable for benching. For instance, loose soils lacking stability could pose a risk of collapse even when cut into benches, making unsupported excavations dangerous. Similarly, in high water table areas, the additional moisture can weaken soil cohesion, undermining the effectiveness of benching. Lastly, rocky soils often require different excavation techniques due to their hardness and may need specialized tools and methods to ensure safe excavation rather than relying on benching.