Site Work, Excavation, and Foundations
Site work questions test soil behavior, excavation safety, and foundation basics. Understand soil classification (granular vs. cohesive), bearing capacity, and why expansive or organic soils require special handling. Know compaction concepts: optimum moisture content, Proctor tests, and lift thickness (commonly 6–8 inches per lift for most equipment).
Master excavation safety: OSHA-style rules require sloping, benching, shoring, or a trench box for trenches 5 feet or deeper, and a competent person must inspect daily. Spoil piles must be kept back (typically at least 2 feet from the edge). Know the difference between cut and fill and how to compute shrinkage and swell - excavated soil expands (swell) when disturbed and later compacts (shrinkage), so bank, loose, and compacted volumes differ.
Understand foundation types: spread footings, mat foundations, pile/deep foundations, and when each is used. Know frost depth requirements and drainage (footing drains, waterproofing, grading away from the structure). Understand the purpose of vapor barriers and capillary breaks under slabs.
Worked rule of thumb: If bank volume is 100 cubic yards and soil swells 25% when excavated, loose volume = 125 cubic yards - important for trucking and haul-off cost. If it shrinks 15% when compacted, compacted volume ≈ 85 cubic yards from the same bank volume.
Traps: ignoring swell/shrink; assuming trenches under 5 feet need no protection; forgetting frost depth; misjudging bearing capacity.