Experimental study of the soil structure variable z used in constitutive models such as Neohypoplasticity or Sanisand

The tensorial state variable z stores the current soil structure or fabric in constitutive models. This study presents macroscopic monotonic undrained triaxial tests on sand samples subjected to different cyclic preloading. The data demonstrates that a pronounced drained cyclic preloading practically erases z and effects the fabric induced by the preparation method. In contrast, a less pronounced undrained cyclic preloading do not impact the fabric induced by the preparation method. Using the results, evolution equations of corresponding state variables in constitutive models can be adapted.