A trench is being excavated in previously disturbed backfill material. What soil classification would this typically fall under, and what implications does it have for sloping or shoring?

Question: A trench is being excavated in previously disturbed backfill material. What soil classification would this typically fall under, and what implications does it have for sloping or shoring?

Answer options:

• A. Type A; requires minimal shoring.
• B. Type B; requires moderate shoring or sloping at 1H:1V. ✅ C. Type C; requires significant shoring or sloping at 1.5H:1V or flatter.
• D. Solid rock; no shoring needed.

Correct answer: C. Type C; requires significant shoring or sloping at 1.5H:1V or flatter.

Explanation: Previously disturbed backfill is generally classified as Type C soil due to its lack of cohesion and unpredictable stability. This classification demands the most conservative approach to trench safety, often requiring extensive shoring or a very shallow slope (1.5H:1V or flatter) to prevent cave-ins.