This article introduces a novel system identification technique for determining the bulk modulus of cohesionless soils in the post-liquefaction dissipation stage following seismic excitation. The proposed method employs a discretization of Biot's theory for porous media using the finite difference method. The technique was validated using synthetic data from finite elements simulations of an excited soil deposit. These numerical simulations were performed using an advanced multi-yield surface elastoplastic model. Additionally, the technique was used to analyze a series of high-quality dynamic centrifuge tests performed on Ottawa F-65 sand as part of the LEAP- 2020 project. A comparative analysis between recorded and identified bulk modulus values highlights the effectiveness of the proposed technique across a wide range of conditions.

Elastic moduli, e.g. shear modulus G and bulk modulus K, are important parameters of geotechnical materials, which are not only the indices for the evaluation of the deformation ability of soils but also the important basic parameters for the development of the constitutive models of geotechnical materials. In this study, a series of triaxial loading-unloading-reloading shear tests and isotropic loading-unloadingreloading tests are conducted to study several typical mechanical properties of coral calcareous sand (CCS), and the void ratio evolution during loading, unloading and reloading. The test results show that the stress-strain curves during multiple unloading processes are almost parallel, and their slopes are much greater than the deformation modulus at the initial stage of loading. The relationship between the confining pressure and the volumetric strain can be defined approximately by a hyperbolic equation under the condition of monotonic loading of confining pressure. Under the condition of confining pressure unloading, the evolution of void ratio is linear in the e-lnp' plane, and these lines are a series of almost parallel lines if there are multiple processes of unloading. Based on the experimental results, it is found that the modified Hardin formulae for the elastic modulus estimation have a significant deviation from the tested values for CCS. Based on the experimental results, it is proposed that the elastic modulus of soils should be determined by the inter line of two spatial surfaces in the G/K-e-p'/pa space (pa: atmosphere pressure). Ye formulation is further proposed for the estimation of the elastic modulus of CCS. This new estimation formulation for soil elastic modulus would provide a new method to accurately describe the mechanical behavior of granular soils. (c) 2024 Institute of Rock and Soil Mechanics, Chinese Academy of Sciences. Production and hosting by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/ licenses/by-nc-nd/4.0/).