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Rankine Passive Earth Pressure & Shear Key Calculator

Compute Rankine passive earth pressure coefficient Kp, passive resisting thrust, shear key depth contribution, and factor of safety against sliding.

Effective internal angle of friction of foundation soil.

Moist bulk unit weight of foundation soil resisting sliding.

Depth of footing base below downstream ground surface.

Vertical depth of shear key projecting below footing base.

Total base width of retaining wall footing.

Total horizontal driving force attempting to slide the wall.

Calculated Result
3.255

Rankine Passive Coeff (Kp)

Total Passive Thrust

123.67 kN/m

Toe Embedment Thrust

44.52 kN/m

Shear Key Increment

79.15 kN/m

Sliding FS Contribution

0.75

Calculation Breakdown

  1. Rankine Passive Earth Pressure CoefficientK_p = tan²(45° + φ/2) = tan²(45° + 16.0°) = 3.255
  2. Passive Earth Pressure Thrust MobilizationP_p(toe) = 0.5 · γ · D_f² · K_p = 44.52 kN/m; P_p(key) = 79.15 kN/m; Total P_p = 123.67 kN/m
  3. Design Passive Contribution to Sliding Factor of SafetyDesign P_p / Driving Load = (123.67 / 1.5) / 110 = 0.75

Passive Soil Thrust Breakdown

Interactive visualization based on your current inputs

kN/m
0.0316293124Kp (x10)Toe Embedment (kN/m)Shear Key (kN/m)Total Passive (kN/m)Thrust ComponentkN/m

What Is the Rankine Passive Earth Pressure & Shear Key Calculator?

Compute Rankine passive earth pressure coefficient Kp, passive resisting thrust, shear key depth contribution, and factor of safety against sliding.

The Rankine Passive Earth Pressure & Shear Key Calculator is an analytical tool in the physics domain designed to evaluate Soil Friction Angle (φ), Soil Unit Weight (γ), Toe Embedment Depth (Df), Shear Key Depth (d_key), Footing Base Width (B), Driving Lateral Force using verified mathematical equations. It provides reproducible, deterministic calculations for academic, professional, and practical applications.

How Does the Rankine Passive Earth Pressure & Shear Key Calculator Work?

This calculator computes results by taking input values for Soil Friction Angle (φ), Soil Unit Weight (γ), Toe Embedment Depth (Df), Shear Key Depth (d_key), Footing Base Width (B), Driving Lateral Force and applying the governing equation: Rankine passive earth pressure coefficient and total triangular passive resistance mobilized across toe and shear key embedment.. Values are checked for dimensional consistency and processed through standard arithmetic routines.

Rankine Passive Earth Pressure & Shear Key Calculator Formula & Variables

The core mathematical equation utilized by this calculator is expressed as:

Kp=tan2(45°+φ/2),Pp=0.5⋅γ⋅(Df+dkey)2⋅KpKp = tan²(45° + φ/2), Pp = 0.5 · γ · (Df + d_key)² · Kp

Rankine passive earth pressure coefficient and total triangular passive resistance mobilized across toe and shear key embedment.

How to Use the Rankine Passive Earth Pressure & Shear Key Calculator

  1. Enter your value for Soil Friction Angle (φ) in °.
  2. Enter your value for Soil Unit Weight (γ) in kN/m³.
  3. Enter your value for Toe Embedment Depth (Df) in m.
  4. Enter your value for Shear Key Depth (d_key) in m.
  5. Enter your value for Footing Base Width (B) in m.
  6. Enter your value for Driving Lateral Force in kN/m.
  7. Verify your input parameters to ensure they match your design or problem specifications.
  8. Review the calculated results, intermediate mathematical steps, and graphical visualization below.

Step-by-Step Example Calculation

Cantilever Wall with Shear Key (φ = 32°, Df = 1.2m, d_key = 0.8m)

Input Values:

internalFrictionAnglePhiDeg:32
soilUnitWeightKNPerM3:19
embedmentDepthDFM:1.2
shearKeyDepthDKeyM:0.8
foundationWidthBM:3.5
lateralDrivingForceKN:110
Worked Steps: Computes Kp = 3.255, toe thrust = 44.5 kN/m, shear key thrust = 79.2 kN/m, total Pp = 123.7 kN/m.

Understanding Your Result

The calculated output gives the primary solution for Rankine Passive Earth Pressure & Shear Key under the specified conditions. Use this value to compare against standard design tolerances, benchmarks, or reference ranges in physics.

Factors That Affect the Result

  • Input precision and measurement accuracy of Soil Friction Angle (φ), Soil Unit Weight (γ), Toe Embedment Depth (Df), Shear Key Depth (d_key), Footing Base Width (B), Driving Lateral Force.
  • Operating conditions, environmental parameters, and specific physics tolerances.
  • Boundary constraints and deviations from nominal theoretical model assumptions.

When Should You Use This Calculator?

  • When performing technical analysis or dimensioning related to Rankine Passive Earth Pressure & Shear Key.
  • To cross-verify manual calculations or theoretical models in physics.
  • For preliminary estimates before conducting detailed field measurements or laboratory testing.

Assumptions & Limitations

  • Mobilizing full passive resistance requires horizontal wall movement of 1% to 5% of embedment depth. In design, passive thrust is typically derated by a factor of 1.5 to 2.0.
  • Soil in front of the toe must be well compacted and protected against future frost or utility trench excavation.

Frequently Asked Questions

Where should a shear key be located along the footing base?+
A shear key is typically placed beneath the wall stem or under the heel, ensuring that the passive failure wedge does not intersect the active failure wedge behind the wall.
Why is passive resistance often neglected in sliding checks?+
Engineers often neglect passive soil at the toe if future utility excavation, landscaping, or scour might temporarily remove downstream overburden.

Calculation Accuracy & Reference Note

This calculator implements verified mathematical formulas for Rankine Passive Earth Pressure & Shear Key Calculator. Always verify critical results against official domain standards and manufacturer documentation.

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