OSHA's trench safety materials point out that one cubic yard of soil can weigh as much as a car. Most soils weigh roughly 100 to 130 pounds per cubic foot depending on type and moisture, or about 2,700 to 3,500 pounds per cubic yard. This calculator uses a simple wedge model to estimate how much soil comes down when a section of trench wall fails.
How the estimate works
When a vertical trench wall fails, a wedge of soil usually breaks away along a crack some distance back from the edge. OSHA's Technical Manual notes that tension cracks typically form about 0.5 to 0.75 times the trench depth back from the edge. The calculator treats the failing soil as a triangular wedge:
- Wedge volume = ½ × depth × (crack distance) × length of wall that fails
- Weight = volume × soil unit weight
What this means for the crew
- No one can hold back or outrun that much soil. Protection must be in place before entry.
- Even partial burial can stop breathing and cause crush injuries.
- Water makes soil heavier and weaker, so wet trenches are more dangerous, not less.
This is an awareness tool, not a design method. Protective systems must be designed from OSHA's appendices, tabulated data or a registered professional engineer. Learn why walls fail in trench cave-ins.
Sources and official references
Last reviewed: October 25, 2026 · Free general education based on OSHA 29 CFR 1926 Subpart P. It does not replace the site-specific training and competent person your employer must provide, and it does not issue a certificate. Nothing you enter on this page is saved or sent.