For linear strain-softening geomaterials at post-peak
the total shear strain in the shear band(localized shear zone) is composed of the elastic strain(described by the classical elastic theory) and the local plastic shear strain due to the microstructural effect(described by the nonlocal theory or gradient-dependent plasticity).If the shear softening modulus(the absolute value of the slope of the shear stress-plastic shear strain curve) is less than two times of the shear elastic modulus
then two constant shear strain points exist in any section of a shear band.At the two points
the total shear strain is independent of the shear stress;the decrease of the elastic shear strain and the increase of the local plastic shear strain reach an equilibrium state;and the total shear velocity reaches its maximum or minimum value.With a decrease of the shear stress rate
the total shear velocity increases between the two constant shear strain points.In the shear band
the velocity distribution is nonlinear
as it is different from the traditional assumption of linear velocity distribution(neglecting the microstructural effect).
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