Secondary collapses are most closely linked to which process during a structural collapse?

• A. Winds and weather
• B. Normal settlement and shifting debris
• C. Groundwater intrusion
• D. Fire progression

Answer: (B)

Secondary collapses are driven by the ongoing movement of the debris after the initial failure. As the rubble settles under its own weight and blocks shift, loads are redistributed and new voids collapse, causing previously stable portions to lose support and fail. This continual settling and shifting is the primary mechanism that leads to additional collapses within the collapse zone. While other factors like wind, groundwater, or fire can influence conditions, they do not as directly drive secondary collapse as the system continues to settle and rearrange debris.