What soils can be easily and safely excavated?

• A. Calcareous sand
• B. Wet silts
• C. Firm clays and tills with low moisture content
• D. Sand with high moisture content

Answer: (C)

The ability to excavate safely depends on the soil’s stability, which is greatly improved when the soil is cohesive and has low moisture content. Firm clays and tills resist slipping and cave-ins when they’re dry because their internal bonding and friction are higher, so trenches can be dug with less risk and without extensive shoring.

Wet or loose soils are much more prone to failure. Wet silts have reduced shear strength and can slump or flow into the trench, while sand with high moisture can behave like quicksand, losing support for trench walls. Calcareous sand, if it’s dry, may be workable but when wet it becomes unstable and harder to excavate safely.

So, the best choice for easy and safe excavation is soils that are firm and cohesive with low moisture content, like firm clays and tills.