Abstract
This paper presents a bounding surface model predicting the combined effects of cementation and partial saturation on the mechanical behaviour of soils subjected to isotropic loading. The loss of cementation caused by loading, wetting or drying of a normally consolidated soil is described by a “cementation bonding function”. This states that, under virgin conditions, the ratio between cemented and uncemented void ratios monotonically decreases with increasing levels of scaled stress. The scaled stress is the variable governing the intrinsic behaviour of the soil under both saturated and unsaturated conditions. Combination of the cementation bounding function with a previously proposed model for unsaturated soil behaviour leads to the formulation of a “cemented unified normal compression line” (CUNCL). This describes the virgin behaviour of both cemented and uncemented soils under saturated and unsaturated conditions. Progressive yielding is modelled by assuming that the slope of the generic loading curve tends towards the slope of the CUNCL as the soil state moves from overconsolidated to virgin conditions. The model has been calibrated and validated against existing experimental data demonstrating a good ability to predict the void ratio of cemented soils during isotropic loading, unloading and wetting under both saturated and unsaturated conditions.
Highlights
Soils are often found in nature in a cemented state and under partially saturated conditions
This paper has presented a bounding surface model capable of predicting the combined effect of cementation and partial saturation on the mechanical behaviour of soils subjected to isotropic stress states
The model is based on the definition of a cementation bonding function that relates cemented and uncemented void ratios under virgin conditions
Summary
Soils are often found in nature in a cemented state and under partially saturated conditions. Over the last three decades, researchers have developed constitutive laws that predict the gradual loss of soil cementation under increasing loads [1,2,3,4,5,6,7,8,9,10,11] These models neglect the effect of partial saturation on the mechanical behaviour of cemented soils. The complete model requires seven parameters, which have a clear physical meaning and are relatively easy to calibrate Three of these parameters govern the mechanical behaviour of the unsaturated uncemented soil under virgin conditions, which is here referred to as the “intrinsic behaviour” [28]. Further work is needed to couple the present mechanical law with a water retention law (similar to [30]) and incorporate non-isotropic stress states so that a complete hydromechanical framework for cemented unsaturated soils can be developed
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