Metric and Imperial Units

The above formulas may be used with both imperial and metric units. As with all calculations care must be taken to keep consistent units throughout with examples of units which should be adopted listed below:

Notation

• I_W = Westergaard stress co-efficient
• P = total concentrated load, kip or kN
• r = horizontal distance to point of interest from load, ft or m
• z = vertical distance from load to point of interest, ft or m
• µ_s = Poisson’s ratio of the soil between the reinforcements
• ∆σ = stress increase at point of interest, kip/ft² or kPa