29 CFR 1926 Subpart P (Excavations & Shoring)
OSHA Trenching & Soil Mechanics Calculator
Engineered for competent persons, excavation foremen, and utility contractors. Calculate allowable slope angles, top-of-trench cuts, Rankine lateral earth pressure on shoring shields, and generate verified daily inspection sign-off logs.
Protective System Status
Required (≥5 ft)
29 CFR 1926.652(a)(1)
Max Allowable Slope
1 : 1 (45°)
Type B Soil
Lateral Pressure (Base)
480 psf
At Trench Invert
Required Egress Ladders
3 Ladders
≤ 25 ft Lateral Travel
1. OSHA Soil Classification
Type B: Cohesive soil with unconfined compressive strength 0.5–1.5 tsf, angular gravel, silt, silt loam, or previously disturbed soil (except Type C).
Moist Soil Unit Weight (γ)
120 pcf
Internal Friction Angle (φ)
30°
2. Trench Dimensions & Geometry
Trench Depth (H)
8.0 ft
≥5 ft mandates protective systems (sloping/benching/shielding)
Trench Bottom Width (B)
4.0 ft
Trench Linear Length (L)
100 ft
Surcharge Load (Spoil pile / Equipment)
100 psf
OSHA mandates spoils ≥2 ft setback; heavy excavators add 100–300 psf
3. Trench Box / Shield Rating Verification
Manufacturer Shield Rating
1,200 psf
Shield Capacity Check
PASSED
Trench box rating (1,200 psf) exceeds maximum calculated lateral earth pressure (480 psf).
Excavation Engineering Results
Required Top Width
20.0 ft
8.0 ft cut per side
Excavation Volume
356 CY
~480 tons of spoil
Rankine Ka Coeff
0.333
EFP: 40.0 psf/ft
Max Lateral Pressure
353 psf
Thrust: 1,413 lbs/lf
Min Spoil Setback
2.0 ft
29 CFR 1926.651(j)(2)
Egress Ladder Count
3 Units
Extends 3 ft above rim
Excavation Cross-Section & Sloping Diagram Slope 1:1 (45°)
Ground Level: Top Width = 20.0'
Bottom Width = 4.0'
Depth = 8.0'
OSHA Competent Person Daily Trench Inspection Checklist
Soil classified by visual/manual tests (Appendix A)
Spoil piles & equipment placed ≥2 ft from edge
Ladders located within 25 ft of lateral travel
No evidence of fissure cracks, sloughing, or boiling
Water accumulation checked / pump operational
Underground utilities located & marked (811)
Competent Person: _________________________
Date: 2026-09-16
Status: SAFE FOR ENTRY