Parameters of constitutive models are generally obtained by comparing results of numerical forward simulations with measurement data. Often the parameter values are varied by trial-and error in order to reach an improved fi t and to obtain plausible results. However, the description of complex soil behavior requires advanced constitutive models (e.g. ). The rising complexity of these models mainly increases the number of unknown constitutive parameters. Thus an effi cient “by hand” identification becomes quite difficult for most practical problems.