Questions And Correct Answers (Verified
Answers) Plus Rationales 2026 Q&A | Instant
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1. Which soil type typically has the highest risk of collapse in an
excavation?
A. Gravel
B. Sand
C. Clay
D. Silt
B. Sand
Sand is granular, loose, and does not hold its shape well, making it
prone to collapse without proper shoring.
2. What is the primary purpose of a bench in excavation work?
A. Reduce labor costs
B. Improve aesthetics
C. Increase stability of the slope
D. Speed up excavation
C. Increase stability of the slope
Benching helps reduce the risk of soil failure by creating stepped
slopes, distributing the load and improving stability.
3. Which OSHA regulation primarily governs excavation safety?
A. 1926 Subpart P
B. 1910 Subpart D
C. 1926 Subpart L
, D. 1910 Subpart Z
A. 1926 Subpart P
OSHA’s Subpart P sets standards specifically for excavation and
trenching safety.
4. What is the function of a trench box?
A. Provide storage
B. Protect workers from cave-ins
C. Guide machinery
D. Improve soil compaction
B. Protect workers from cave-ins
Trench boxes create a protective barrier that prevents soil from
collapsing onto workers.
5. How often should inspections of active excavations be conducted?
A. Once per week
B. Daily and after any hazard occurrence
C. Monthly
D. Only before work begins
B. Daily and after any hazard occurrence
Inspections ensure safety conditions are maintained and any
changes in soil or site conditions are addressed.
6. What is the maximum allowable slope for Type C soil in a 20-foot
deep excavation without protective systems?
A. 1:1 (45°)
B. 1.5:1 (34°)
C. 0.75:1 (53°)
D. 1:1.5 (33°)
C. 0.75:1 (53°)
, Type C soil is the least stable; OSHA allows steeper slopes only with
protective systems.
7. Which soil classification is considered the most stable for
excavation?
A. Type A
B. Type B
C. Type C
D. Sand
A. Type A
Type A soils are cohesive and have high unconfined compressive
strength, reducing the risk of collapse.
8. What is the primary hazard associated with water accumulation in
an excavation?
A. Soil compaction
B. Reduced productivity
C. Cave-ins
D. Soil discoloration
C. Cave-ins
Water reduces soil strength, increases weight, and can trigger
collapse if not properly drained.
9. When is it necessary to use shoring in an excavation?
A. Only for excavations deeper than 10 feet
B. When sloping is not feasible or soil is unstable
C. Only in sandy soils
D. Shoring is optional
B. When sloping is not feasible or soil is unstable
, Shoring provides structural support to prevent trench collapse
when natural slopes cannot safely hold.
10. What is a key indicator of soil Type B?
A. Cohesive soil with cracks
B. Soft, granular, non-cohesive soil
C. Hard, stable clay
D. Compacted gravel
A. Cohesive soil with cracks
Type B soils are moderately stable but can fail if disturbed or
saturated.
11. Which protective system is suitable for a 15-foot excavation
in Type C soil?
A. Sloping only
B. Shielding (trench box)
C. Shoring
D. Both B and C
D. Both B and C
Trench shields or shoring are required to safely protect workers in
deep excavations with unstable soils.
12. The purpose of compaction in earthwork is to:
A. Increase soil permeability
B. Decrease soil strength
C. Improve soil stability and support structures
D. Reduce soil temperature
C. Improve soil stability and support structures
Proper compaction increases soil density, reduces settling, and
enhances load-bearing capacity.