During site planning for the MAAS, if the soils fall below a 7 CBR value what else is planned?

During site planning for the MAAS, if the soils fall below a 7 CBR value what else is planned?

• A. Installation of a deadman
• B. Concrete raft foundation
• C. Increased ballast
• D. No change

Answer: (A)

When soil strength is low, you must change how loads from the structure are resisted. A California Bearing Ratio (CBR) below a certain threshold indicates the surface soil isn’t reliable for carrying the required loads, so the design adds an anchor that works with deeper, more stable soil. A deadman is a buried anchor that the structure is tied to with a tension member. By transferring load to deeper formations, it increases pullout resistance and prevents the structure from tilting or pulling out under wind, tension, or other forces. This approach is chosen over others because it directly improves lateral and uplift resistance without relying on weak surface soil. A concrete raft foundation would spread load but still depends on the surface soil’s bearing capacity and involves extensive excavation and concrete, which may be unnecessary or impractical for this situation. Increased ballast adds weight to the structure but doesn’t significantly enhance resistance to overturning or pullout in weak soils. No change would leave the structure vulnerable to movement or failure. Thus, installing a deadman provides the needed anchorage given the weak soil condition.

When soil strength is low, you must change how loads from the structure are resisted. A California Bearing Ratio (CBR) below a certain threshold indicates the surface soil isn’t reliable for carrying the required loads, so the design adds an anchor that works with deeper, more stable soil. A deadman is a buried anchor that the structure is tied to with a tension member. By transferring load to deeper formations, it increases pullout resistance and prevents the structure from tilting or pulling out under wind, tension, or other forces.

This approach is chosen over others because it directly improves lateral and uplift resistance without relying on weak surface soil. A concrete raft foundation would spread load but still depends on the surface soil’s bearing capacity and involves extensive excavation and concrete, which may be unnecessary or impractical for this situation. Increased ballast adds weight to the structure but doesn’t significantly enhance resistance to overturning or pullout in weak soils. No change would leave the structure vulnerable to movement or failure. Thus, installing a deadman provides the needed anchorage given the weak soil condition.