Creep of shale and sandy-shale

Nishihara, Masao

doi:10.5575/geosoc.58.373

Cited by 50 publications

(20 citation statements)

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“…is the directional visco-elastic strain and is derived from Nishihara model (Nishihara, 1952(Nishihara, , 1957, which can be written as follows:…”

Section: Non-linear Stress-strain Relation For Anisotropic Coalmentioning

confidence: 99%

“…Permeability measurements were performed before and after the change in the effective stress. Creep is normally modelled through exponential (Bai et al, 2012;Brantut et al, 2013;Li et al, 2011;Li et al, 2013;Nishihara, 1952Nishihara, , 1957Yin et al, 2009;Yin et al, 2008) and power functions (Cruden et al, 1987;Singh, 1975;Wang et al, 2011). Classical Nishihara model, as shown in Fig.…”

Section: Introductionmentioning

confidence: 99%

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Characterisation of creep in coal and its impact on permeability: An experimental study

Danesh

Chen

Connell

et al. 2017

International Journal of Coal Geology

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ABSTRACT:Creep is a time-dependent deformation that affects coal permeability and should be considered in the prediction of Coalbed Methane (CBM) production. This study experimentally characterises and quantifies the impact of creep on coal permeability. The experiments were conducted on a bituminous coal sample, excavated from Bowen Basin, Australia, using a triaxial gas rig equipped with strain and displacement transducers. Two different types of gasses (helium and methane) were injected into the sample under various stress and pore pressure conditions. It was found that for the experiments with helium, creep caused permanent partial closure of cleats and pathways under constant effective stress, and hence a reduction in permeability. Under hydrostatic stress only, a Residual Deformation Ratio (RDR) of 14.1% and a Permeability Loss Ratio (PLR) of 71% were found following the removal of the axial load. This can be due to the damage to coal microstructure along with closure of cleats. For the experiments with methane, coal experienced an instantaneous elastic deformation, at the onset of pore pressure depletion, followed by consolidation and matrix shrinkage. Then, creep occurred when gas desorption ceased. A total permeability loss of 26% was achieved due to an increase of 1.91 MPa in effective stress caused by gas desorption. In addition, the model previously developed by authors was validated against the experimental permeability data. A good agreement was found between the model-predicted permeability data and the experimental permeability data, particularly for higher pore pressure ranges.Keywords: Coal permeability; creep; consolidation; triaxial test; gas desorption

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“…is the directional visco-elastic strain and is derived from Nishihara model (Nishihara, 1952(Nishihara, , 1957, which can be written as follows:…”

Section: Non-linear Stress-strain Relation For Anisotropic Coalmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Characterisation of creep in coal and its impact on permeability: An experimental study

Danesh

Chen

Connell

et al. 2017

International Journal of Coal Geology

View full text Add to dashboard Cite

show abstract

“…Widely used models include the Kelvin, Burgers, Nishihara, Sterpi and Gioda models [9,10]. Among these models, significant attention has been given to the Nishihara model [1] (Fig. 1) due to its simplicity and ability to provide a clear, comprehensive reflection of the elastic-viscoelastic-viscoplastic features of rock rheology.…”

Section: Introductionmentioning

confidence: 99%

“…Rock rheology refers to the time-dependent properties of flow, deformation and failure with respect to varying temperature and/or external loading conditions within geological formations; as such, it comprises examination of phenomena such as creep, relaxation, residual elasticity and aging strength, among which creep [1] is defined as 'continuously increasing strain with respect to time under constant external stresses'. Due to the direct engineering implications of rock creep, it now represents a significant research area within rock rheology [2,3].…”

Section: Introductionmentioning

confidence: 99%

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A New Accelerating Creep Constitutive Model and its Parameters Sensitivity Analysis

Shen¹,

Wang²,

Zhang³

2014

Proceedings of the 2014 International Conference on Mechanics and Civil Engineering

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Abstract. In this study, Perzyna visco-plasticity theory and Nishihara component model were combined to establish a universal creep constitutive model for describing the entire process of creep, including transient creep, steady-state creep and accelerating creep. Based on the internal energy theory, the constitutive model defined the critical internal energy density value of accelerating creep to describe the mutation characteristics of materials' creep behavior and predict the time of accelerating creep effectively. Overall, the numerical simulation results agreed with the experimental data. Furthermore, according to the sensitivity analysis of parameters, such as flow rule, cohesive force, internal friction angel and Poisson's ratio, and study the constitutive equation change rule with the change of major parameters to further verify the rationality of model. Research shows that, the flow rule and internal friction angle have influence on the time of accelerating creep, and the influence law is close to a parabola form. But the influence law shows a straight line form for the cohesive force and Poisson's ratio. The flow rule, cohesive force and internal friction angle affect steady-state creep strain rate, and the influence law is close to a straight line form. However, Poisson's ratio has no effect on it. The parameters sensitivity of steady-state creep strain rate from small to large in the order is Poisson's ratio, flow rule, cohesive force and internal friction angle. But the sequence turns into Poisson's ratio, cohesive force, flow rule and internal friction angle for the time of accelerating creep.

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Study of the 1‐D consolidation behavior of two‐layered soft soils: Parametric studies using a rheological model with viscoplastic body

Zou

Xie

et al. 2018

Num Anal Meth Geomechanics

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Summary The governing equations for the coupled processes of consolidation and creep of two‐layered soft soils are established. The Nishihara rheological model is adopted to simulate the elasto‐viscoplastic characteristics of soft soils, disregarding the effects of the soil self‐gravity. A semi‐analytical theory combined with numerical and analytical methods is introduced to solve the governing equations of the one‐dimensional rheological model. The computational procedure and the approximate solutions for two‐layered soft soils subjected to surface loading are obtained for two drainage conditions. The solutions and the computational procedure are used to study the effects of the two layers and constitutive parameters on rheological consolidation behavior of soft soils. It can be concluded that two layers affect the rate of excess pore water pressure dissipation and settlement development. The parametric studies show that when the parameters of the upper layer remain constant, increases in the permeability and elastic modulus in the lower layer accelerate the dissipation of the excess pore water pressure, and meanwhile increases in the viscosity coefficient and viscoplastic limit slows down the dissipation of the excess water pressure.

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Creep of shale and sandy-shale

Cited by 50 publications

References 0 publications

Characterisation of creep in coal and its impact on permeability: An experimental study

Characterisation of creep in coal and its impact on permeability: An experimental study

A New Accelerating Creep Constitutive Model and its Parameters Sensitivity Analysis

Study of the 1‐D consolidation behavior of two‐layered soft soils: Parametric studies using a rheological model with viscoplastic body

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