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The deformation modulus E_v

The deformation modulus E_v is a parameter for the deformability of the soil. Decisive – for the assessment of compression – is both the ratio of the values E_v2: E_v1, and the value E_v2. According to DIN 18134 E_v is determined by a polynomial of 2nd degree and the method of least squares. The physical unit is NM/m².
E_v = 0,75 * (plate diameter D [mm]) * (Difference of the normal stress between the loads of 0,3*σ_max and 0,7*σ_max [MN/m²]) / (Difference of the settlement of the load plate at these load steps [mm]).

The deformation modulus M_E
The deformation modulus M_E is a parameter for the deformability of the soil. (Switzerland, Slovenia)
M_E = (plate diameter D [mm]) * (Difference of the normal stress between two loads [MN/m²}) / (Difference of the settlement of the load plate at these load steps [mm])

The deformation modulus M_D
The deformation modulus M_E is a parameter for the deformability of the soil. (Italy)
M_D = (plate diameter D [mm]) * (Difference of the normal stress between two loads [MN/m²}) / (Difference of the settlement of the load plate at these load steps [mm])

The deformation modulus E_v1, E_v2, E_v3
E_v1 is the modulus of the first load cycle of the plate load test. Physical unit is MN/m².
E_v2 is the modulus of the second load cycle of the plate load test. Physical unit is MN/m².
E_v3 is the modulus of the third load cycle of the plate load test. Physical unit is MN/m². (rare)

Subgrade reaction k_s
The Westergaard’s modulus of subgrade reaction k_s is a parameter of the resilience of the soil surface under a distributed load. The average normal stress at a settlement of the load plate of 1.25 mm is measured. (according to DIN18134). The diameter of the load plate is typically 762mm.