Civil: Geotechnical PE

Free Civil: Geotechnical PE equations calculator for PE exam prep. 58 formulas with Excel templates, worked examples, and exam tips.

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All Civil: Geotechnical PE Equations (58)

Frequently Asked Questions

How do I use Active Earth Pressure (Cohesionless) on the PE exam?

This is fundamental for retaining wall design. Remember Ka depends on soil friction angle φ and wall friction δ. For quick estimates, use Ka ≈ 1/3 for typical sands. Always check if the problem gives Ka directly or requires calculation from φ using Rankine or Coulomb theory.

How do I use Active Earth Pressure (Cohesive) on the PE exam?

For cohesive soils, active pressure can be negative near the surface due to the cohesion term. The critical depth where pressure becomes zero is zc = 2c/(γ√Ka). Above this depth, tension cracks may form. Always check if your calculated pressure is physically reasonable.

How do I use Allowable Bearing Capacity on the PE exam?

This is a fundamental equation used in nearly every foundation design problem on the PE exam. Ultimate bearing capacity is typically given or calculated from Terzaghi or other bearing capacity equations. Common factors of safety range from 2.0-4.0 depending on soil conditions and foundation type. Watch for problems where you need to solve backwards for required FS.

How do I use At-Rest Earth Pressure Coefficient on the PE exam?

Jaky's formula applies only to normally consolidated soils. For overconsolidated soils, use K₀(OC) = K₀(NC) × OCR^0.5. Remember that K₀ values typically range from 0.3-0.8 for most soils - values outside this range should be questioned.

How do I use Average End Area Method on the PE exam?

Most common on PE Civil Construction exam. Remember to convert ft³ to CY by dividing by 27 for English units. Cross-sectional areas are typically given or must be calculated from station elevations and ground profiles.