SettingsSettings for this calculationUS
The total (moist) unit weight of the retained soil — γ, not its dry density.
Common soils typically fall between 17 and 20 kN/m³, which is roughly 108 to 127 pcf. Use a project-specific geotechnical report for the actual value — this is not a value the calculator should assume for a real design.
The soil's internal friction angle, in degrees, used in the Rankine active pressure coefficient.
This formula assumes cohesionless (granular) soil. Sand typically ranges 28-40°. This value must come from a geotechnical report — it cannot be reliably assumed from visual soil classification alone.
The vertical height of the excavation face or shoring wall being checked.
Measured from the base of the cut to the ground surface (or top of the shoring), assuming a horizontal ground surface with no surcharge.
Total active lateral force per unit length of wall
1,900 lbf/ft
This is a preliminary Rankine active-pressure estimate for COHESIONLESS soil under simplified conditions (no water table, no surcharge, vertical smooth wall) — a screening/educational estimate, NOT a stamped design. Cohesive soils, groundwater, surcharge loads (equipment, spoil piles, adjacent structures), sloped ground, braced/strutted multi-level systems (which use Peck's empirical apparent-pressure diagrams instead), and seismic loading all require different methods not captured here. Per OSHA 29 CFR 1926 Subpart P, the actual excavation protective system must be selected by a competent person using the Subpart P tables or designed by a registered professional engineer using site-specific geotechnical data — this calculator is not a substitute for that process.
- Peak lateral pressure at base of cut
- 381.95 psf
- Active pressure coefficient Ka
- 0.33 (dimensionless)
They open the calculator with your figures already in it
Excavation Shoring Lateral Active Soil Pressure Calculator (Rankine): 1,910 lbf/ft — shown in imperial, US market. The link sets both, so the result they see is the one on your screen.
Show calculation logicHide calculation logic
How this was calculated
Formula source(s)
- Rankine active earth pressure theory for a cohesionless soil, vertical smooth wall, horizontal ground surface, no surcharge, no water table: Ka = tan²(45° − φ/2); peak pressure at base p_max = γ×H×Ka; total active force per unit length of wall Pa = 0.5×γ×H²×Ka. This is the standard textbook formula (used in the Caltrans Trenching and Shoring Manual and standard geotechnical references). OSHA 29 CFR 1926 Subpart P classifies soil by Type A/B/C using field tests (unconfined compressive strength), NOT by friction angle or Ka — the actual protective system must be selected per Subpart P's prescriptive tables or designed by a registered professional engineer (1926.652(b)/(c)); this formula is not itself an OSHA-published method.
Inputs used
- Soil Unit Weight γ
- 114.59 pcf
- Soil Internal Friction Angle φ (°, Typical Range 28-40° for Sand — Requires a Geotechnical Report)
- 30
- Excavation/Retained Height
- 10 ft
Intermediate steps
- Peak lateral pressure at base of cut
- 381.95 psf
- Active pressure coefficient Ka
- 0.33 (dimensionless)
Confidence note: This is a preliminary Rankine active-pressure estimate for COHESIONLESS soil under simplified conditions (no water table, no surcharge, vertical smooth wall) — a screening/educational estimate, NOT a stamped design. Cohesive soils, groundwater, surcharge loads (equipment, spoil piles, adjacent structures), sloped ground, braced/strutted multi-level systems (which use Peck's empirical apparent-pressure diagrams instead), and seismic loading all require different methods not captured here. Per OSHA 29 CFR 1926 Subpart P, the actual excavation protective system must be selected by a competent person using the Subpart P tables or designed by a registered professional engineer using site-specific geotechnical data — this calculator is not a substitute for that process.
What this calculation does not cover
- There is no water in this model. Below a water table the soil pushes with its buoyant weight, but the water adds its own full hydrostatic pressure on top, and Ka does not reduce that part — the load on a saturated face is much higher than the figure here. Perched water, seepage through a granular lens, and a table that rises after rain are not checked at all.
- No surcharge is included. Spoil heaped along the crest, an excavator or crane tracking beside the cut, stacked pipe, site traffic, and the footings of any adjacent structure all add lateral load this ignores. On a tight site the surcharge can be the larger part of the total.
- Active pressure only develops if the wall moves enough to let the soil behind it relax. A stiff or tightly propped wall that cannot yield attracts at-rest pressure, which is substantially higher, and a multi-level braced excavation is designed to an apparent-pressure envelope of a different shape entirely. Size a strut off this triangular distribution and it comes out light.
- The formula is for cohesionless granular soil against a vertical smooth wall with level ground. It carries no cohesion term, no wall friction, no allowance for sloped or benched ground above the cut, and no layering — clay, silt and mixed fill do not behave this way, and a cohesive face standing unsupported for a shift is not evidence the pressure is low.
- This is a pressure figure, not a shoring design. It does not size sheets, soldier piles, wales, struts or anchors, does not set embedment depth below formation, applies no factor of safety, and checks nothing for toe stability, base heave or overall slope failure. Under OSHA 29 CFR 1926 Subpart P the protective system must come from the Subpart P tables, a trench shield manufacturer's tabulated data, or a registered professional engineer's design.
Add the equipment this sizes
This result is a specification — 1,900 lbf/ft — not a quantity. Put the thing it sizes into your project: how many, what you call it, and your supplier’s price.
Computed in your browser — nothing you enter is uploaded. Presented in US customary units and US trade terminology. Where a formula follows a published standard, that standard and its edition are cited beside it on this page; where none governs, the page says so. Local amendments override model codes — verify against the code in force where you build.
Sources checked 2026-09-02 · in the site-wide review of 2026-09-06 · v1.0.1
Regulatory standards & verification citations1
- Rankine active earth pressure theory for a cohesionless soil, vertical smooth wall, horizontal ground surface, no surcharge, no water table: Ka = tan²(45° − φ/2); peak pressure at base p_max = γ×H×Ka; total active force per unit length of wall Pa = 0.5×γ×H²×Ka. This is the standard textbook formula (used in the Caltrans Trenching and Shoring Manual and standard geotechnical references). OSHA 29 CFR 1926 Subpart P classifies soil by Type A/B/C using field tests (unconfined compressive strength), NOT by friction angle or Ka — the actual protective system must be selected per Subpart P's prescriptive tables or designed by a registered professional engineer (1926.652(b)/(c)); this formula is not itself an OSHA-published method.
Cite this page
Your workspace
Most jobs need more than one number. Add the calculators you need next and they open right here, underneath this one — your figures stay on screen and nothing is lost to a page change.