Page 150 - RoadCem Manual - PCT BV

Determination due to shock in the sub-base
Permanent deformation can occur in the sub-base as a result of compaction that leads too deformation. These processes can happen independently or in combination. The criteria is developed to predict when the longitudinal plane (smooth or rough) has increased to IRI=3,5. The fatigue relation for a subsoil is modelled as follows:
Where:
∑log( Ni)=0,5⋅log( Nv)+0,5⋅log( Nl) N=i
log( Nf )=(−6,211 −0,482 ⋅z−4⋅log(εf ))+ log( Ne)=(−6,211 −0,482 ⋅z−4⋅log(εe))
Formula 5.1 Determining shock in the sub-base
Z = For the z-score a reliability level of 70 % is accepted.
εf = Vertical shock above sub-base with fully loaded truck (50% of the total amount of trucks).
εl= Vertical shock above sub-base with empty loaded truck (50% of the total amount of trucks). Nv= Permitted amount load repetitions based on sub-base shock.
RoadCem can prevent deformation from happening depending on the composition of the sub-base.
Deformation in unbound foundation
With unbound foundations permanent deformations must be prevented. The calculation of resistance against moldable deformation is shown in the formula 5.2. When the pressure ratio is smaller than 0,6 then the construction suffices compared to the permanent deformation of the unbound foundation.
R= σ1 −σ3 σ1f −σ3
Formula 5.2 Determining deformation in unbounded foundation.
R = Pressure ratio
σ1= highest (mainly vertical) main pressure with fully loaded truck (kPa);
σ3= least (mainly horizontal) main pressure, with fully loaded truck (kPa);
σ1f= Maximum permitted main pressure for the foundation material is accepted at 1.700 kPa, this is the same as cement granulate.
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