Creep-based permeability evolution in deep coal under unloading confining pressure

Zhou, Hongwei; Wang, L.J.; Rong, Tenglong; Zhang, L.; Ren, W.G.; Su, Teng

doi:10.1016/j.jngse.2019.03.010

Cited by 46 publications

(14 citation statements)

References 25 publications

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“…At present, with the reduction of shallow resources, many mines have begun to turn to the exploitation of deep resources. The mining depth has approached or exceeded 1000 m, and there is a trend toward deeper mining 12,13 . Deep rock masses are in a more complex environment, and there exist many engineering instability problems.…”

Section: Introductionmentioning

confidence: 99%

A state‐of‐the‐art review on creep damage mechanics of rocks

Zhou

Pan

Berto

2022

Fatigue Fract Eng Mat Struct

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In many major rock projects, services have spanned decades or even hundreds of years. For engineering design, it is necessary not only to ensure the safety of personnel during construction but also to ensure the safety of long‐term use and operation in the future. Therefore, it is indispensable to study the creep damage mechanical properties of rocks before the construction of the project. For a long time, rock creep has been an important reason for large deformation and even instability in building foundations, underground tunnels, and slopes. Moreover, the surrounding rock generally exhibits obvious creep damage characteristics under an environment of high stress, high temperature, and high water‐pressure. Under certain geological conditions, this creep damage behavior is extremely prominent. Therefore, the study of rock creep damage mechanics is very important. This paper reviews the advancement of rock creep damage mechanics from the aspects of mechanisms, research methods, constitutive models, and so forth. Rock creep is a process of interaction between structural damage and the hardening effect. The structural damage and hardening effect are opposite to each other, but they exist in the same physical process. The creep research method introduces mainly the research objects, influencing factors, monitoring methods, and experimental methods. Creep constitutive models introduce mainly empirical models, linear element combination models, nonlinear combination models, and other nonlinear models based on new theory. Finally, based on the current research progress, several important research directions in rock creep damage mechanics are pointed out.

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Section: Introductionmentioning

confidence: 99%

A state‐of‐the‐art review on creep damage mechanics of rocks

Zhou

Pan

Berto

2022

Fatigue Fract Eng Mat Struct

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“…In deep underground engineering, the creep deformations of rocks become more common due to the high stress (He et al 2005). The time-dependent deformations of rocks negatively affect the mining safety (Li et al 2017;Mishra and Verrna 2015;Sainoki and Mitri 2017;Zhou et al 2019), backfill mining (Guo et al 2019;Sun et al 2013), coalbed methane production (Danesh et al 2016(Danesh et al , 2017Guo et al 2018;Kang et al 2015), and geo-sequestration (Liu et al 2015;Sone and Zoback 2014). Consequently, to enhance the understanding of this phenomenon is of importance to guarantee the stability of underground engineering.…”

Section: Introductionmentioning

confidence: 99%

Experimental investigation on the nanoindentation viscoelastic constitutive model of quartz and kaolinite in mudstone

Sun

Gomah

et al. 2021

Int J Coal Sci Technol

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The creep behaviors in deep underground engineering structures, especially in soft rocks, have a remarkable impact on the long-term stability of the excavations, which finally leads to the high risk and failure of it. Accordingly, it is essential to recognize the time-dependent deformation through the investigation of this phenomenon. In this study, the creep behaviors of soft rocks were examined to help understand the underlying mechanism of the extended time-dependent deformation. Due to the limited results about the time-dependent properties of the constituents of the rock that reveal their heterogeneity, the targeting nanoindentation technique (TNIT), was adopted to investigate the viscoelastic characteristics of kaolinite and quartz in a two-constituent mudstone sample. The TNIT consists of identifications of mineralogical ingredients in mudstone and nanoindentation experiments on each identified constituent. After conducting experiments, the unloading stages of the typical indentation curves were analyzed to calculate the hardness and elastic modulus of both elements in mudstone. Additionally, the 180 s load-holding stages with the peak load of 50 mN were transformed into the typical creep strain–time curves for fitting analysis by using the Kelvin model, the standard viscoelastic model, and the extended viscoelastic model. Fitting results show that the standard viscoelastic model not only can perfectly express the nanoindentation creep behaviors of both kaolinite and quartz but also can produce suitable constants used to measure their creep parameters. The creep parameters of kaolinite are much smaller than that of quartz, which causes the considerable time-dependent deformation of the soft mudstone. Eventually, the standard viscoelastic model was also verified on the quartz in a sandstone sample.

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“…In recent years, creep behaviour has been studied in many rocks, such as shale, 12–16 salt, 17–19 sandstone, 11,20–23 granite, 24–26 basalt, 27 tuff, 28–30 limestone, 31,32 claystone 33,34 and coal‐rock 35–37 . Although the strength parameters of different rocks are different, the characteristics of their creep curves are essentially identical for all these major types of rocks 21,38 .…”

Section: Introductionmentioning

confidence: 99%

“…[7][8][9][10][11] In recent years, creep behaviour has been studied in many rocks, such as shale, [12][13][14][15][16] salt, [17][18][19] sandstone, 11,[20][21][22][23] granite, [24][25][26] basalt, 27 tuff, [28][29][30] limestone, 31,32 claystone 33,34 and coal-rock. [35][36][37] Although the strength parameters of different rocks are different, the characteristics of their creep curves are essentially identical for all these major types of rocks. 21,38 Sandstone is a type of sedimentary rock, which is mainly composed of various sand grains, and is widely used in various rock engineering.…”

Section: Introductionmentioning

confidence: 99%

Damage analysis of sandstone during the creep stage under the different levels of uniaxial stress using NMR measurements

Cheng

Zhou

Pan

et al. 2020

Fatigue Fract Eng Mat Struct

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In this paper, the nuclear magnetic resonance (NMR) measurements are carried out to evaluate the micro‐cracking characteristics of sandstones during the creep stage under the different levels of creep stresses. The variations in the parameters, including transverse relaxation time (T2) spectra distribution, percentage of the pore distribution, incremental value of porosity and ultrasonic P wave velocity are analysed. The results show that, during the creep stage, small pores in the rocks gradually evolve into large pores, resulting in an increase in damage of rocks. With the increase of the loading ratio, the increasing rate of porosity increases sharply, implying that the damage degree becomes more serious under the high loading ratio. When the loading ratio is larger than 0.7, the increasing rate of porosity and the decreasing rate of the P wave velocity both increases rapidly. During the creep stage, the relationship between micro‐crack and macro‐creep characteristics of rocks is established based on the analysis of the deformation and the porosity evolution during creep. It is found that, as the loading ratio increases, the increasing rate of porosity is linear with the creep strain. The NMR method offers a feasible option to identify micro‐cracking process of rocks during the creep stage, which can directly reflect the damage mechanism of rock caused by creep. The porosity of rocks is an effective parameter to evaluate the damage of rocks. The damage evolution of the specimen is highly anisotropic and is heavily related to the loading ratio during the creep stage. The relationship between the damage parameter and the loading ratio is exponential.

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Creep-based permeability evolution in deep coal under unloading confining pressure

Cited by 46 publications

References 25 publications

A state‐of‐the‐art review on creep damage mechanics of rocks

A state‐of‐the‐art review on creep damage mechanics of rocks

Experimental investigation on the nanoindentation viscoelastic constitutive model of quartz and kaolinite in mudstone

Damage analysis of sandstone during the creep stage under the different levels of uniaxial stress using NMR measurements

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