Pore Water Pressure Degradation Parameters

Matasovic (1993) represents the degradation of the shear strength and shear stiffness of the soil within the MKZ model by inclusion of two degradation indices. These degradation parameters have also been implemented (and have similar effects) within the GQ/H model. The degradation parameters are defined as:

	Eq. 1
	Eq. 2

Where 𝛿_𝐺 is the shear modulus degradation function, 𝛿_𝜏 is the shear stress degradation function, 𝑢^∗ is the excess pore water pressure normalized by initial effective overburden stress, and 𝑣 is a curve-fitting parameter to better model the degradation of shear strength with excess pore pressure generation.

These degradation parameter formulations are implemented for all soil models except the Matasovic and Vucetic model for clays. The degradation parameters for the Matasovic and Vucetic model for clays are defined by Matasovic (1995) as:

𝛿𝐺 = 𝛿𝜏 = 𝑁−1

Eq. 3

Where 𝛿_𝐺 is the shear modulus degradation function, 𝛿_𝜏 is the shear stress degradation function, and 𝑁 is the number of equivalent cycles.