Time variations of the K0 coefficient in overconsolidated clays due to morphological evolution of slopes

The incision of a natural or an artificial slope in a clay deposit initiates a morphological evolution and determines variations of the internal state of stress in the deposit. This evolution can be analyzed considering the variations over time of the lateral stress at rest coefficient K0. This paper is focused on the evolution of the K0 in overconsolidated clay deposits submitted to the incision of natural slopes. The proposed idea is that, under specific morphological and evolutionary conditions, a value of K0 < 1 could be considered reliable even for medium–high OC clay deposits. This idea is here discussed with the support of in-situ and laboratory data from: i) pressuremeter tests performed in overconsolidated clay deposits in Central Italy and ii) a scaled physical modeling experiment reproducing a normally consolidated clay deposit. This study suggests that when dealing with clay deposits subjected to a simultaneous vertical and horizontal unloading due to slope incision, the K0 coefficient should be considered a parameter variable as a function of the different stress–strain evolutions experienced by each portion of the deposit. The portions involved in the slope incision had different evolutions and are represented by different K0 values. As a consequence, diverse amounts of decrease distinguish the evolution of the K0 for natural rather than artificial slopes.