OSHA 10-Hour Construction ReviewExcavationsMedium
A trench is being excavated in soil that is mostly granular, with little to no clay content, and is easily crumbled. A competent person would most likely classify this soil as:
- AType A
- BStable Rock
- CType B
- DType C
Show answer & explanationAnswer & explanation
Correct answer: D. Type C
The description 'mostly granular, with little to no clay content, and is easily crumbled' aligns with the characteristics of Type C soil. Type C soils are granular soils like sand and gravel, or submerged soil, that are the least cohesive and most prone to collapse.
Why the other options are wrong
- A. Type A soil is cohesive, like clay, and has high compressive strength, unlike the described soil.
- B. Stable rock is solid mineral matter, not crumbly granular soil.
- C. Type B soil has some cohesive properties but is less stable than Type A; the description points to even less cohesion.
Type C Soil Characteristics
Type C soil is the least stable soil type, characterized by granular soils (sand, gravel), submerged soil, or cohesive soil with very low unconfined compressive strength (<0.5 tsf). It crumbles easily and lacks cohesion.
- Granular soils (sand, gravel).
- Low or no clay content.
- Easily crumbled, lacks cohesion.
- Least stable soil type.
- Requires steepest slopes or most robust protective systems.
Memory trick: Rocks and A, B, C's of Soil Safety