Final answer:
Trench excavation safety guidelines commonly recommend keeping excavated material at least 2 feet from the trench edge, but specific distances can vary based on soil conditions, trench depth, and regulations.
Step-by-step explanation:
The distance for which excavated material should be kept back from the edge of any trench excavation is not directly addressed in the provided references, as they pertain to historical earthwork in a different context. However, in modern engineering and construction safety practices, it is commonly recommended that excavated soil or materials (often called "spoils") be kept at least 2 feet (0.6 meters) away from the edge of an excavation. This distance can vary depending on the soil type, depth of the trench, and local regulations or engineering practices. It is essential to consult with contemporary safety guidelines, such as those established by the Occupational Safety and Health Administration (OSHA) or equivalent authority in one's country or region, for specific requirements.
Trench safety is critical to prevent collapses or cave-ins, and factors like soil stability, presence of water, and weight of the spoil piles should be considered when determining the safe setback distance. Sufficient space from the trench edge can also provide safe access for workers and help prevent accidents related to material roll-back into the trench.