Dear Hockley,
The Winkler modulus can be estimated by the following expression:
K = E*(1/B+1/L+1/h)
where,
K : Winkler modulus [kN/m3]
E : average Young modulus of the soil [kN/m2]
B : width of the strip [m]
L : length of the strip [m]
h : limit depth of the soil [m]
The expression may be used...