Heaving or boiling at the bottom of an excavation is an indication of imminent _______.

Heaving or boiling at the bottom of an excavation is an indication of imminent _______.

• A. failure
• B. stability
• C. settlement
• D. drainage

Answer: (A)

Heaving or boiling at the bottom of an excavation shows the soil mass is losing its ability to support the loads, meaning the shear strength has been exceeded and a cave-in is imminent. It’s a direct indicator of instability in the trench, not a gradual process like settlement, nor primarily a drainage issue. So the best fit is failure.

Heaving or boiling at the bottom of an excavation shows the soil mass is losing its ability to support the loads, meaning the shear strength has been exceeded and a cave-in is imminent. It’s a direct indicator of instability in the trench, not a gradual process like settlement, nor primarily a drainage issue. So the best fit is failure.