Abstract
In sand constitutive models, it is of cardinal importance to consider a state parameter to distinguish the real dilatancy for cohesionless soils (sand), which is different from cohesive soils (clay). Thus, one of the key issues in simulating the sand behaviour is the better representation and parameter calibration of critical state line (CSL) for estimating contraction in loose state and dilatancy in dense state, respectively. For this purpose, a new exponential form for CSL with two model constants a and b has been presented in the literature. This paper provides a valuable insight into the two model constants, controlling the shape of the critical state line by simulating a uniform quartz reference sand (Hostun RF) in loose and dense states under undrained triaxial conditions. It can be concluded that the liquefaction behaviour in loose state is fundamentally affected by even a minor variation in model constant a , but insensitive to model constant b . Moreover, the linear fitting calibration of CSL recommended in the literature is complicated in consideration of the non-unified critical state line. Thus, the maximum void ratio in the natural state could be considered as a comparison basis on which to evaluate the liquefaction potential as an alternative. The numerical results showed good agreement with real experimental data. However, in dense state, the dilatant behaviour of sand was found to be mainly controlled by model parameter b . In addition, the influence of a non-unified critical state under various confining pressures on the determination of b should not be neglected. With the correction of b , the numerical results were found to be consistent with the experimental data concerning Hostun RF sand.
Highlights
Unlike metal materials, the shear strength of natural silica sand is controlled by internal frictions.Subjected to a relatively low loading, the destruction of sand specimens is caused by relative sand particle movements, instead of particle crushing
During an earthquake, much of the severe damage of geotechnical structures can be attributed to sand liquefaction, which results in large land deformations due to positive excess pore water pressure
The present work presents a parameter evaluation of two model constants based on the exponential form ofThe critical state line
Summary
The shear strength of natural silica sand is controlled by internal frictions. A state parameter containing both the effect of void ratio and confining pressure should be carefully taken into account in the dilatancy law d = d(η, ψ, M) for sand. The simplification of the former leads to multiple sets of model parameters because the same sands in loose and dense states are treated as totally different materials. One of the fundamental issues in sand constitutive modelling is the precise representation of critical state line in terms of the effective confining pressure ec = ec (p0 ) Plotting these lines of cohesionless sand in e − log p0 plan makes the expression algebraically more difficult. The description of the model [9] used in this paper is briefly given followed by a detailed synthesis of the effect of the models parameters on critical state
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