What is the purpose of 'benching' in excavation, and how does it enhance worker safety?

The purpose of 'benching' in excavation is to create a series of horizontal steps or levels (benches) in the sides of an excavation, primarily to prevent cave-ins and protect workers from the hazard of collapsing soil. Benching is a soil stabilization technique used when the excavation is deeper than a certain depth, which varies depending on the soil type and local regulations. The depth threshold is set because deeper excavations are more prone to collapses due to the increased pressure exerted by the soil. Each bench reduces the overall slope angle of the excavation wall, making it more stable. Instead of a single, steep slope, the excavation wall is divided into a series of smaller, less steep slopes separated by horizontal benches. This reduces the risk of soil sliding or collapsing. The width of each bench and the height of each vertical cut are determined based on the soil type and the angle of repose (the steepest angle at which a material can be piled without slumping). Stable soil types allow for higher vertical cuts and narrower benches, while less stable soil types require lower cuts and wider benches. Benching enhances worker safety by providing a stable and less hazardous working environment. Workers are less likely to be injured or killed by a cave-in when benching is properly implemented. It provides a wider and more level surface for workers to stand and move around, reducing the risk of slips, trips, and falls. It also creates a physical barrier that can help to contain small soil slides or collapses, preventing them from reaching the workers. Benching is often used in conjunction with other soil stabilization techniques, such as shoring (supporting the excavation walls with timber or steel) and sloping (cutting the excavation walls at a gradual angle). These combined techniques provide maximum protection against cave-ins and ensure a safe working environment.