Bonding Structured UH Model

Bonding in structured soil limits the relative motion between soil particles as deformation develops with loading. This makes the structured soil behave differently from the reconstituted soil. Based on the unified hardening (UH) model for overconsolidated soils, a new model is proposed to describe the stress-strain relations of structured soil. The new model is developed from the following aspects: (a) a moving normal compression line (MNCL) paralleling to the traditional normal compression line (NCL) in e-lnp plane is proposed by introducing a structure potential parameter to describe soil structure collapse in isotropic compression; (b) a moving critical state line (MCSL) paralleling to the traditional critical state line (CSL) in p−q plane is proposed by introducing a bonding parameter to describe stress ratio evolution influenced by bonding in shear. This parameter is adopted in the dilatancy equation to consider the bonding-dependent dilatancy of structured soil. Both of the above 2 structure parameters have clear physical meanings and can be determined or estimated by conventional tests. It has been analyzed that the proposed model is able to smoothly and continuously reflect the positive/negative dilatancy and strain hardening/softening of structured soil influenced by bonding and its decay.