Which of the following poses a significant risk of trench collapse?

Excavating without proper protective systems poses a significant risk of trench collapse because it ignores essential safety protocols designed to prevent such incidents. Trench excavation is inherently hazardous due to the potential for soil instability. If workers do not implement protective measures such as shoring, shielding, or proper sloping, the walls of the trench can fail, leading to a collapse. The lack of structural support means that even minor disturbances, such as vibrations from nearby equipment or changes in moisture content, can trigger a catastrophic failure.

Using safety barriers, properly sloping the trench walls, and regular monitoring of soil conditions are all practices that enhance safety during trenching operations. Each of these measures is intended to prevent collapse by either supporting the soil structure, reducing the angle at which the soil can fail, or by keeping track of changing conditions that could compromise trench stability. Therefore, these practices are crucial for creating a safe work environment, while the absence of appropriate protective systems significantly increases the likelihood of a collapse.