A bounding surface mechanical model for unsaturated cemented soils under isotropic stresses

This paper presents a model that describes the gradual yielding of unsaturated cemented soils subjected to isotropic loading. The model relies on the definition of a “cementation bonding function” which accounts for the progressive breakage of inter-granular cementation caused by loading. The combination of this cementing bonding function with the unsaturated model of Gallipoli and Bruno (2017) leads to the formulation of a “cemented unified normal compression line” (CUNCL), which describes the virgin behaviour of both cemented and uncemented soils under saturated and unsaturated conditions. Gradual yielding is described by assuming that, as the soil state moves towards the CUNCL, the slope of the loading curve tends towards the slope of the CUNCL. The model describes the hysteretic variation of void ratio for both cemented and uncemented soils under saturated and unsaturated conditions by using only seven parameters, i.e. five parameters for the uncemented behaviour plus two extra parameters accounting for the effect of cementation. The model has been calibrated and validated against the experimental data of Arroyo et al. (2013) demonstrating a good performance to describe the uncemented and cemented behaviour of soils under saturated and unsaturated conditions.