Experimental Researches on Long-Term Strength of Granite Gneiss

Liu, Lin; Xu, Weiya

doi:10.1155/2015/187616

Cited by 18 publications

(12 citation statements)

References 28 publications

(25 reference statements)

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“…Granite gneiss is a candidate material for underground oil, CO 2 and shale gas storage and radioactive waste disposal, because of its low permeability (Liu and Xu 2015;Tsang et al 2005).…”

Section: Introductionmentioning

confidence: 99%

Permeability Evolution of Granite Gneiss During Triaxial Creep Tests

Liu

Wang

et al. 2016

Rock Mech Rock Eng

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Permeability is an important factor for seepage analysis of rock material, and a key factor in ensuring the safety of underground works. In this study, the permeability evolution of granite gneiss during triaxial creep tests was investigated. In the context of an underground oil storage cavern in China, a series of hydro-mechanical coupling creep tests were conducted on rock cores of granite gneiss at three different pore pressures to reveal the effect of pore pressure on the permeability evolution and to investigate the correlation between the permeability and volumetric strain during the creep process. During the creep tests, the permeability decreases in the initial loading phase. At all deviatoric stress levels, the permeability remains stable in the steady creep stage and increases rapidly in the accelerated creep stage. Based on the test data, the initial permeability, steady permeability and peak permeability at various stress levels are defined. The effect of pore pressure on the permeability is captured by a linear model. In addition, the relationship between permeability and volumetric strain can be described as a process divided into three phases, with different functions in each phase.

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“…Granite gneiss is a candidate material for underground oil, CO 2 and shale gas storage and radioactive waste disposal, because of its low permeability (Liu and Xu 2015;Tsang et al 2005).…”

Section: Introductionmentioning

confidence: 99%

Permeability Evolution of Granite Gneiss During Triaxial Creep Tests

Liu

Wang

et al. 2016

Rock Mech Rock Eng

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“…Szczepanik et al 44 found that dilatancy occurred when the loading was 70-80% of the uniaxial compressive strength, and this stress point can be regarded as its LTS. Generally, the determining method can be classified as (1) unsteady deformation method 45 ; (2) the stress threshold method (σ cd ) 46,47 ; and (3) the isochronal stress-strain curves method (ISSCM) according to the creep experimental results [48][49][50] . www.nature.com/scientificreports www.nature.com/scientificreports/ To better understand the influence of stress level on the long-term strength, the isochronal stress ratio-strain curves of the intact specimen and fissured rock with various fissure dip angles are plotted in Fig.…”

Section: Lts Of Red Sandstone Containing a Single Fissure Lts Is An mentioning

confidence: 99%

Creep and permeability evolution behavior of red sandstone containing a single fissure under a confining pressure of 30 MPa

Yang

2020

Sci Rep

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The long-term deformation and permeability evolution with time are key issues for geo-engineering applications such as radioactive waste disposal. Rock permeability concurrent with deformation is significantly influenced by cracking. This study investigated the creep-permeability evolution behavior of red sandstone specimens containing a single fissure under a confining pressure of 30 MPa. First, the effects of stress ratio (SR) and fissure dip angle on the creep behavior of rock were investigated. The more loading/unloading cyclic numbers, the larger the irrecoverable axial deformation. The instant elastic strains and visco-elastic strains linearly increased with SR for both the intact and fissured specimens, whereas the instant plastic strains showed different results. The visco-plastic strains nonlinearly increased. For fissured and intact specimens, the creep strains and the steady-state creep rates nonlinearly increased as SR increased. The instantaneous strains, instant elastic strains, and visco-elastic strains slightly varied when the fissure dip angle was less than 45° but notably decreased with increasing fissure dip angle beyond 45°. However, the fissure dip angle had no obvious effects on the plastic and creep strains. Damage (D) was defined using the ratio of non-elastic strains to the total strain. D increased approximately linearly with SR, but the fissure dip angle had no obvious influences. Subsequently, the long-term strength (LTS) of the red sandstone was determined using two different methods. The LTS first decreased when the fissure dip angle increased from 0 to 45° but increased with increasing dip angle. The triaxial and creep failure modes were mainly shear along anti-wing cracks for the fissured specimens but shear failure occurred for the intact specimen. Moreover, the permeability of the fissured red sandstone was governed by SR and deformation or time. During the multi-step loading/unloading creep process, the permeability first decreased and then had a sudden rise when tertiary creep occurred.

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“…To solve the problem mentioned above, Liu and Xu [35] introduced a method named intersection method of steady creep rate based on the steady-state rate method. With this method, the stress value corresponding to the intersection point between the fitted curves of steady-state axial strain rate and steady-state volumetric strain rate under different levels of deviatoric stress is defined as the long-term strength of rocks.…”

Section: Long-term Strengthmentioning

confidence: 99%

Modified Nishihara Rheological Model considering the Effect of Thermal‐Mechanical Coupling and Its Experimental Verification

Wang

Huang

Lian

et al. 2018

Advances in Materials Science and Engineering

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The effect of temperature and pressure, which play important roles in the mechanical properties of rocks during deep energy exploitation, has not been sufficiently studied in the previous rock creep models. In order to investigate thermal effect in creep models, a modified Nishihara rheological model, taking into account the coupled effect of thermal damage and stress, was proposed by combining the theoretical formula for thermal damage of rocks with the modified Nishihara model. The improved model introduces a nonlinear viscous dashpot, which can accurately describe the accelerated rheological phase of rocks. To verify the proposed model, a triaxial rheological experiment was conducted on sandstone subjected to thermal damage (600°C). In addition, the stress-strain curves within whole creep process of the rheological experiment were analyzed. Furthermore, the theoretical curves of the modified Nishihara rheological model were compared with the experimental results. Results showed that the theoretical curves relatively agree well with the experimental data, suggesting that the proposed new model is more preferred to describing the rheological curve of sandstone subjected to thermal damage at different rheological stages, in particular, it is capable of depicting the accelerated rheological stage of the sandstone, providing a good ability to describe the creep behavior of rocks under thermal-mechanical coupling.

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Experimental Researches on Long-Term Strength of Granite Gneiss

Cited by 18 publications

References 28 publications

Permeability Evolution of Granite Gneiss During Triaxial Creep Tests

Permeability Evolution of Granite Gneiss During Triaxial Creep Tests

Creep and permeability evolution behavior of red sandstone containing a single fissure under a confining pressure of 30 MPa

Modified Nishihara Rheological Model considering the Effect of Thermal‐Mechanical Coupling and Its Experimental Verification

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