Excavation & Grading
Excavation and grading shape the ground and build the foundation the pavement sits on.
The pavement structure
A pavement is a stack of layers, each spreading load to the one below:
Top → bottom: surface (asphalt/concrete) · base course (compacted aggregate base) · subbase (optional select layer) · subgrade (native soil or compacted fill). Loads spread out as they go down, so stronger material goes on top and the subgrade sees the least stress.
Grading and fill
Grade control keeps the work at the correct elevation and slope. When placing fill against an existing slope, the slope is cut into level steps — benching (keying) — so the new fill locks in and won’t slide. Fill and trench backfill go in compacted lifts, not one loose dump.
Before any digging, the contractor must determine the estimated location of underground utilities (OSHA 29 CFR 1926.651 and California’s USA/811 dig law) — see the excavation safety topic for the trench-protection rules that follow.
Practice: Excavation & Grading
Frequently asked
What are the layers of a pavement structure?
Why is fill benched into an existing slope?
What must you do before opening an excavation?
More C-12 Earthwork & Paving topics
Planning & Estimating Earthwork
C-12 study guide on planning and estimating earthwork: reading plans, cut and fill, balancing a site, shrink and swell factors, percent grade, and project layout.
Read & practice →Soils & Compaction
C-12 study guide on soils and compaction: the Proctor test, maximum dry density, optimum moisture content, relative compaction, standard vs modified Proctor, and lifts.
Read & practice →Paving & ADA
C-12 study guide on paving: asphalt vs concrete pavement, prime and tack coats, base failure causes, concrete joints, and ADA slope limits for ramps, parking, and cross slope.
Read & practice →Excavation Safety (OSHA)
C-12 study guide on OSHA trench and excavation safety: when a protective system is required, soil types and slopes, the competent person, access and egress, spoil placement, water, and atmospheres.
Read & practice →Stormwater & Environmental
C-12 study guide on construction stormwater: when a site needs Construction General Permit coverage, the SWPPP and QSD/QSP roles, and erosion control vs sediment control BMPs.
Read & practice →Work-Zone Traffic Control
C-12 study guide on work-zone traffic control for paving and roadway jobs: orange signs, taper length, the flagger's STOP/SLOW paddle, and channelizing device spacing.
Read & practice →