Page 151 - RoadCem Manual - PCT BV
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 Figure 5.38 Deformation in unbound foundation.
Cracking of upper edge for bound foundation
When using an emulsion layer on the foundation material the stress from the traffic load above can become so high that cracking occurs and ruts can develop. The formula 5.3 is a method of calculating the lifespan relative to this condition with approx. 10 mm rutting on the upper edge of the foundation.
∑log(NCA)i =0,5⋅log(NCA)full +0,5⋅log(NCA)empty NCA =i
σv2( full) log(NCA)full =(0,894−0,55⋅z)⋅(1−(1,31−0,085⋅z)⋅σd )))
σv2(empty) log(NCA)empty =(0,894−0,55⋅z)⋅(1−(1,31−0,085⋅z)⋅σd )))
Formula 5.3 Crushing upper edge bounded foundation.
NCA = Permissible number of load repetitions until continued cracking
σv2full = Maximum vertical stress in the upper edge of the foundation and bearing strength of the sub-base.
σv2empty = Maximum vertical stress in the upper edge of the foundation with an empty truck, this value depends on the thickness and bearing strength of the foundation and bearing strength of the sub-base.
  σd z =
= Pressure strength of the foundation material; it is assumed that the minimum pressure strength is 2 MPa.
A reliability level for the z-score is 70%.
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