A homogenization‐based state‐dependent model for gap‐graded granular materials with fine‐dominated structure

Abstract

Gap‐graded granular soils are common natural soils composed of cohesionless granular matrix and rock aggregates. Since they are widely used as construction materials worldwide, their deformation behavior is crucial for the design of civil infrastructures. There have been rare constitutive models reported for gap‐graded granular soils in the literature. This study presents a homogenization‐based state‐dependent model within the elastoplastic framework. The model features a homogenization equation with a structure parameter and a novel state‐dependent dilatancy function to describe the behavior of granular matrix. Simulations of the model reveals that the initial stiffness and peak shear strength of gap‐graded soils rely on both the coarse fraction and the initial density of granular matrix. The structure parameter is related to the internal structure of gap‐graded soils, and it varies with the particle shape, and particle size distribution of rock aggregates. A higher value of the structure parameter indicates a more distinct coarse fraction effect of rock aggregates, that is, higher initial stiffness, higher peak shear strength, and higher residual shear strength. For a given coarse fraction, the critical states can be well fitted by a straight line through the origin, and the critical state strength parameter Mm increases with the rising rock fraction. A practical method is further proposed for the critical state line of gap‐graded granular soils in e‐p′ compression plane. The proposed model is validated by using experimental data from the literature, including the soils with various densities of sand matrix, different particle size, and particle size distribution of rock aggregates. Comparison between measured data and model predictions indicates that the proposed model can well reproduce the stress‐strain relationship and volumetric deformation behavior of sand‐gravel mixtures and soil‐rock mixtures.

Modeling the Compression Behavior of Dredged Sandy Clays Considering the Effect of Initial Water Contents and Sand Fractions

“…Effect of Sand Fraction. The coarse aggregates (e.g., sand and gravel) usually disperse in soft clay matrix of dredged sandy clays with a fine-dominated structure, leading to a decrease of void space and compressibility [4,19,[32][33][34].…”

Review on Stress-Fractional Plasticity Models

“…It can be found from Equation ( 34 ) that also has two chances to reach zero: one is at the phase transformation state with a typical value of the fractional, the other is at the critical state with and . However, unlike the FP-n based on past stress history and other classic state-dependent models [ 8 , 53 , 54 ], Equation ( 34 ) does not require an additional empirical state parameter, e.g., , to capture the state dependence stress-dilatancy of soil, which is the main advantage of the FP-sn approach.…”

“…It was found that the constitutive responses of geomaterials were state-dependent and non-associated, due to the frictional nature [ 3 , 4 , 5 , 6 ]. The associated plasticity developed for metals could not be simply employed for modelling the stress and strain behaviour of geomaterials [ 7 , 8 ]. Instead, the non-associated plasticity within the framework of critical state soil mechanics was often suggested [ 9 ].…”

How meso shear chains bridge multiscale shear behaviors in granular materials: A preliminary study

“…Contacts between particles give rise to forces with or without the consideration of friction or cohesion, and the statistical characterization of forces and contact network finally result in the stress of the overall assembly. Microscopic features, such as particle size [30,31,32], particle shape [33,34,35] and particle breakage [36,37,38,39], are also recognized to influence the macroscopic mechanical responses. For frictional granular materials, each contact is commonly assumed as elastoplastic, and the sliding is limited by the micro Coulomb friction at the contact scale.…”