Load Bearing Ratio Calculator

Calculate the Load Bearing Ratio (LBR) and bearing stress of soil to ensure structural stability. Supports metric (kPa, m²) and imperial (psf, ft²) units.

kN
mm
m²
Standard
Step by Step
Chart

Result

Detailed Steps

Bearing Stress Comparison

Formula

Load Bearing Ratio Calculation

Load Bearing Ratio (LBR) is calculated as:

LBR (%) = (Applied Load / Standard Load) × 100

Bearing stress is calculated as:

Stress = Applied Load / Foundation Area

Safety check:

Bearing Stress ≤ Allowable Bearing Capacity

Notes:

  • Standard Load: 6.9 MPa (1000 psi) at 2.5 mm (0.1 in) penetration for LBR = 100%.
  • Metric units: kN for load, m² for area, kPa for stress, mm for penetration.
  • Imperial units: kip for load, ft² for area, psf for stress, in for penetration.
  • Allowable bearing capacities:
    • Clay: 50–150 kPa (1044–3132 psf)
    • Sand: 150–400 kPa (3132–8352 psf)
    • Gravel: 400–600 kPa (8352–12528 psf)

How to Use the Load Bearing Ratio Calculator

  1. Select the unit system (Metric or Imperial).
  2. Enter the applied load, penetration depth, and foundation area.
  3. Choose the soil type (Clay, Sand, or Gravel).
  4. Select your preferred display mode (Standard, Step by Step, or Chart).
  5. Click the “Calculate” button.
  6. View the results, including LBR, bearing stress, safety status, and a bar chart comparing stresses.

Frequently Asked Questions (FAQs)

What is the Load Bearing Ratio (LBR)?

The LBR measures a soil’s ability to withstand pressure without significant deformation, expressed as a percentage of the applied load to a standard load (e.g., 6.9 MPa at 2.5 mm penetration).

How is LBR different from CBR?

LBR is similar to the California Bearing Ratio (CBR) but may be adapted for local standards. Both compare soil strength to a standard, with CBR being more common in pavement design.

What is allowable bearing capacity?

It’s the maximum stress a soil can safely support without failure, varying by soil type (e.g., 50–150 kPa for clay, 150–400 kPa for sand).

Why is penetration depth important?

Penetration depth (e.g., 2.5 mm) standardizes the load measurement, ensuring consistent LBR comparisons across soils.

How do I determine soil type?

Soil type is determined through geotechnical testing (e.g., sieve analysis, Atterberg limits). Consult a geotechnical engineer for accurate classification.