NASCLA Commercial General Building Contractor Exam — All Questions
3 questions
Under OSHA's excavation standard, a protective system (sloping, shoring, or shielding) is generally required for a trench at what depth in soil other than stable rock?
- a.5 feet or deeper✓
- b.3 feet or deeper
- c.8 feet or deeper
- d.12 feet or deeper
OSHA's excavation standard (29 CFR 1926 Subpart P) requires a protective system for trenches 5 feet or deeper unless the excavation is entirely in stable rock. For trenches 20 feet or deeper, the protective system must be designed by a registered professional engineer.29 CFR 1926 Subpart P (excavations)
In OSHA's soil classification for excavation safety, which soil type is the most stable and which is the least stable?
- a.Type C is most stable; stable rock is least stable
- b.Stable rock is most stable; Type C is least stable✓
- c.Type A is least stable; Type C is most stable
- d.All soil types are equally stable
OSHA ranks excavation stability from stable rock (most stable) through Type A, Type B, to Type C (least stable). The flatter sloping and stronger protective systems are required as soils get less stable, so correctly classifying the soil drives the protective design.29 CFR 1926 Subpart P (soil classification)
Before placing a slab-on-grade, an engineer specifies that structural fill be compacted to 95% of maximum dry density. Which test establishes that maximum dry density reference?
- a.A slump test
- b.A concrete cylinder break test
- c.A Proctor compaction test✓
- d.A hydrostatic pressure test
The Proctor test (standard or modified) establishes a soil's maximum dry density and optimum moisture content in the lab. Field density tests then compare the compacted fill to that reference, so specifying '95% compaction' is meaningless without a Proctor value to measure against.Soil compaction / Proctor test