Mechanical behaviour of gas-charged fine sediments: model formulation and calibration

Abstract

Multi-phase fluid conditions encountered in geotechnical and geo-environmental problems have led to the development of models that account for the influence of gas solubility and compressibility on the behaviour of soils of various grain sizes. Yet, no consideration has been given to damages related to the nucleation and growth of gas bubbles in fine-grained soils. The purpose of this paper is to present a Cam Clay based constitutive model extended to incorporate such detrimental effects on gassy soils. This is achieved by deriving an analytical expression relating the preconsolidation pressure to a damage parameter dependent on the gas content. That expression is coupled to a deviatoric yield surface accounting for inherent and stress-induced anisotropy. Comparisons of simulations and experimental results attest that introducing a single additional parameter to a conventional Cam Clay type model allows key behavioural features of gas-charged fine sediments to be reproduced.

Strain Rate‐Dependent Hardening‐Softening Characteristics of Gas Hydrate‐Bearing Sediments

“…Numerical GH reservoir simulators have been used to study the behavior of GHBS during gas production (Gupta et al, ; Rutqvist et al, ; Rutqvist et al, ) or in marine slope destabilization (Jiang, Sun, et al, ; Sultan & Garziglia, ; Zander et al, ), and there is strong effort to improve soil mechanical constitutive models and model couplings. A number of nonlinear elastic (Miyazaki, Aoki, et al, ; Yu et al, ) and elasto‐plastic (Klar et al, ; Lin et al, ; Sun et al, ; Uchida et al, ) constitutive models have been proposed.…”

Constitutive modelling of fine‐grained gassy soil: A composite approach

“…The model may be further improved in the following aspects: (a) The model needs to be improved to capture the response of gassy clay under unloading. There gas bubble can expand when the gassy soil is subjected to unloading (eg, decrease of total mean stress during sampling of the gassy soil sample from the sea), which causes damage to the soil structure and affects the soil response during subsequent loading . But the model cannot describe such soil response, because it gives purely elastic response in unloading.…”

“…But the model cannot describe such soil response, because it gives purely elastic response in unloading. Future work will be done to improve the model in this regard based on the work by Sultan and Garziglia and the bounding surface concept; (b) the gas solubility is ignored in this model. When the u w changes during loading, the undissolved gas could get dissolved in the pore water.…”

“…Pietruszczak and Pande have realized that the gas bubbles are larger than the particle size for gassy clays, but their method still cannot capture the detrimental effect of gas bubbles on the undrained shear strength. Sultan and Garziglia proposed a constitutive model that specifically describes the structural damage caused by gas exsolution and expansion because of reduction of total stress (ie, sampling from deep waters). This is achieved by relating the preconsolidation pressure to a damage parameter dependent on the gas content.…”

Model Prediction of Static Liquefaction in Unsaturated Sands

“…Grozic et al [9] proposed a constitutive model for gassy sand based on an existing model. Sultan and Garziglia [13] presented a constitutive model for gassy soil based on Cam-Clay model. This paper studied the onset of static liquefaction in unsaturated sand by proposing a material state-dependent elastoplasticity model.…”