Skip to main content
SpringerLink
Log in

Influence of Liquid Nitrogen Cooling State on Mechanical Properties and Fracture Characteristics of Coal

  • Original Paper
  • Published:
Rock Mechanics and Rock Engineering Aims and scope Submit manuscript

Abstract

To determine the role of LN2-cooling in the fracturing process of the coal, the LN2-cooling process of the coal samples is divided into three states: initial state, frozen state, and freeze–thaw state. Changes in the mechanical properties and fracture behaviors of the coal samples under three states are systematically evaluated by a series of laboratory experiments. The thermal cracking behavior of the coal during LN2 freeze–thaw is revealed through a crack phase-field model. The results indicate that the compressive strength, elastic modulus, and fracture toughness of the frozen coal significantly increase, while they decrease for the freeze–thaw coal. The tensile strength of the coal under the freeze and freeze–thaw states has an obvious reduction, where a greater decrease for the freeze–thaw coal is induced. The fracture propagation process and induced fracture morphology of the coal under both the freeze and freeze–thaw states become complex, in which a greater change for the freeze–thaw coal is presented. The micro-fracture in the coal during LN2-cooling mainly comes from the temperature gradient and mismatch of thermal stress between adjacent mineral particles. Both fracture growth rate and fracture area in the LN2 thaw process are larger than that in the LN2 freeze process. The variations in the fracturing behaviors of the coal with different LN2 treatment states in the mechanical experiments are well explained by the numerical simulation results.

Highlights

  • The mechanical properties of the coal with different LN2 cooling states are studied systematically through laboratory experiments.

  • Effects of the LN2 cooling state on the crack propagation and fracture morphology of the coal in the mechanical tests are analyzed.

  • The micro-crack evolution process of the coal during the LN2 freeze–thaw is revealed through a crack phase-field model.

  • Both the crack propagation rate and induced crack area inside the coal during the LN2 thaw process are greater than that during the LN2 freeze process.

This is a preview of subscription content, log in via an institution to check access.

Access this article

Log in via an institution

Price excludes VAT (USA)
Tax calculation will be finalised during checkout.

Instant access to the full article PDF.

Institutional subscriptions

Fig. 1
Fig. 2
Fig. 3
Fig. 4
Fig. 5
Fig. 6
Fig. 7
Fig. 8
Fig. 9
Fig. 10
Fig. 11
Fig. 12
Fig. 13
Fig. 14
Fig. 15
Fig. 16

Similar content being viewed by others

Abbreviations

CBM:

Coalbed methane

QSGS:

Quartet structure generation set

RA:

Rise time/amplitude

\({\sigma }_{\mathrm{t}}\) :

Tensile strength

\({K}_{\mathrm{I}}\) :

Mode I fracture toughness

\({P}_{\mathrm{max}}\) :

Maximum loading

\(D\) :

Diameter of the disk

\({Y}_{I}\) :

Geometry factor

\(t\) :

Time

\(T\) :

Temperature

\(\overline{T }\) :

Specified boundary temperature

\(\overline{Q }\) :

Specified boundary heat source

\(h\) :

Convective parameter of heat exchange

\(Q\) :

Heat source

\({c}_{\mathrm{p}}\) :

Heat capacity

\(\rho\) :

Density of the coal

\(k\) :

Heat conductivity

\({\mathbf{n}}^{\mathrm{T}}\) :

Normal unit vector

\({\varvec{\upsigma}}\) :

Stress tensor

\({\mathbf{F}}_{\mathrm{V}}\) :

Volumetric force tensor

\(\mathbf{D}\) :

Elasticity modulus tensor

\(\mathbf{u}\) :

Displacement tensor

SEM:

Scanning electron microscope

AE:

Acoustic emission

ISRM:

International Society for Rock Mechanics

AF:

AE counts/duration

\({{\varvec{\upvarepsilon}}}^{\mathrm{e}}\) :

Elastic strain

\({{\varvec{\upvarepsilon}}}^{\mathrm{th}}\) :

Thermal strain

\({T}_{0}\) :

Reference temperature

\({{\varvec{\upalpha}}}_{\mathrm{T}}\) :

Thermal expansion tensor.

\(\phi\) :

Phase field

\(d\left(\phi \right)\) :

Damage function

\({l}_{\mathrm{int}}\) :

Internal length scale

\({H}_{\mathrm{d}}\) :

State variable function

\({G}_{\mathrm{c}}\) :

Critical energy release rate

\({G}_{\mathrm{c}0}\) :

Strain energy threshold

\({W}_{\mathrm{s}0}^{+}\) :

Tensile part of the undamaged elastic strain energy density

\({{\varvec{\upvarepsilon}}}_{\mathrm{el}}^{+}\) :

Tensile part of the elastic strain tensor

\({{\varvec{\upvarepsilon}}}_{\mathrm{el},\mathrm{pi}}\) :

Principal value of the elastic strain tensor

\({\mathbf{n}}_{i}\) :

Direction vector

\(\mathbf{C}\) :

4th order elasticity tensor

\({k}_{0}\) :

Initial thermal conductivity

\(g\left(\phi \right)\) :

Stiffness weakening function

\({\mathbf{D}}_{0}\) :

Initial elasticity modulus tensor

\(\nu\) :

Poisson’s ratio

\(E\) :

Elastic modulus

References

Download references

Acknowledgements

This work had been financially supported by the National Natural Science Foundation of China (51604263, U1762105, and 51904270), the China Postdoctoral Science Foundation (2020M673451), the China University of Mining and Technology [3021802, The Fluidization Mining for Deep Coal Resources], and the Natural Science Foundation of Jiangsu Province (BK20160252).

Author information

Authors and Affiliations

  1. School of Civil Engineering, Xuzhou University of Technology, Xuzhou, 221018, Jiangsu, China

    Shanjie Su & Shengcheng Wang

  2. IPPH, Purdue University, West Lafayette, IN, 47907, USA

    Peng Hou

  3. State Key Laboratory for Geomechanics and Deep Underground Engineering, China University of Mining and Technology, Xuzhou, 221116, Jiangsu, China

    Shanjie Su, Feng Gao, Yanan Gao & Chengzheng Cai

  4. School of Civil Engineering and Architecture, Xi’an University of Technology, Xi’an, 710048, Shaanxi, China

    Xin Liang

Authors
  1. Peng Hou
    View author publications

    You can also search for this author in PubMed Google Scholar

  2. Shanjie Su
    View author publications

    You can also search for this author in PubMed Google Scholar

  3. Feng Gao
    View author publications

    You can also search for this author in PubMed Google Scholar

  4. Xin Liang
    View author publications

    You can also search for this author in PubMed Google Scholar

  5. Shengcheng Wang
    View author publications

    You can also search for this author in PubMed Google Scholar

  6. Yanan Gao
    View author publications

    You can also search for this author in PubMed Google Scholar

  7. Chengzheng Cai
    View author publications

    You can also search for this author in PubMed Google Scholar

Contributions

PH, SS and FG conceived and designed the study. PH performed the numerical simulations and wrote the manuscript. SS, XL and SW carried out the experiment. SS and YG analyzed the experimental results. FG and CC edited this manuscript.

Corresponding author

Correspondence to Shanjie Su.

Ethics declarations

Conflict of Interest

The authors declare that they have no conflict of interest.

Additional information

Publisher's Note

Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Rights and permissions

Reprints and permissions

About this article

Check for updates. Verify currency and authenticity via CrossMark

Cite this article

Hou, P., Su, S., Gao, F. et al. Influence of Liquid Nitrogen Cooling State on Mechanical Properties and Fracture Characteristics of Coal. Rock Mech Rock Eng 55, 3817–3836 (2022). https://doi.org/10.1007/s00603-022-02851-6

Download citation

  • Received:

  • Accepted:

  • Published:

  • Issue Date:

  • DOI: https://doi.org/10.1007/s00603-022-02851-6

Keywords

Search

Navigation