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Rock Mechanics and Rock Engineering

, Volume 52, Issue 1, pp 229–245 | Cite as

Energy Dissipation and Storage in Underground Mining Operations

  • Xiangjian Dong
  • Ali KarrechEmail author
  • Hakan Basarir
  • Mohamed Elchalakani
  • Abdennour Seibi
Original Paper
  • 352 Downloads

Abstract

In this paper, we focus on the energy alteration during longwall mining in an attempt to mimic the conditions of a coal mine in Western Turkey. We verify the proposed model using existing analytical and numerical solutions in terms of stress components. Based on the verified numerical model, the energy balance during longwall retreat is studied rigorously. It is found that excavation-induced increment of external work increases linearly with time, while the stored strain energy increment is quadratic. Meanwhile, the strain energy increment rate gradually decreases with longwall progress because of excavation-induced higher stored energy within the adjacent coal block. The energy dissipation process during lonwall mining, corresponding to crack propagation, is divided into four stages, namely initiation stage, steady growth stage, sharp increment stage, and stabilisation stage. Our results provide new insights into energy evolution during longwall mining both from the reversible and irreversible points of view. The current paper shows, for the first time, that the extended finite element method is suitable to describe the crack propagation during longwall mining. The excavation induced crack propagation in the roof strata predicted by the model is in agreement with the “arch-shaped” patterns obtained using laboratory tests and Discrete Element numerical simulations.

Keywords

Longwall mining Energy dissipation XFEM approach Crack propagation 

List of symbols

\(\sigma ^p_y\)

Vertical stress at the plastic zone

\(\sigma ^e_y\)

Vertical stress at the elastic zone

M

Height of the coal seam

\(\varphi\)

Friction angle

\(\widehat{\sigma }\)

Peak value of concentration stress

\(\sigma _{\text {cm}}\)

Uniaxial compressive strength of coal seam

H

Depth of coal seam

W

Width of extraction

\(\varvec{u}\)

Displacement field

\(\varvec{e}\)

Strain field

\(\varvec{t^*}\)

Boundary traction field

\(\varvec{b^*}\)

Body force field

\(\Omega _{\text {I}}\)

Excavated block region

\(\Omega _{\text {II}}\)

Remaining rock mass region

\(U_{[{\text {e}}]}\)

Stored strain energy

\(W_{[{\text {u}}]}\)

External work

\(\widetilde{W}\)

Extra external work after excavation

\(\widetilde{U}\)

Increased strain energy after excavation

\(W_{\text {r}}\)

Released energy due to excavation

\(N_{\text {I}}(x)\)

Conventional nodal shape function

H(x)

Discontinuous jump function across the crack surfaces

\(F_{\alpha }(x)\)

Elastic asymptotic crack-tip function \(N_{\text {I}}(x)\)

\(\varvec{u_{\text {I}}}\)

Usual nodal displacement vector of function

\(\varvec{a_{\text {I}}}\)

Nodal enriched degree of freedom vector of function H(x)

\(\varvec{b_{\text {I}}^{\alpha }}\)

Nodal enriched degree of freedom vector of function \(F_{\alpha }(x)\)

\(G_{\text {C}}\)

Quasi-static fracture energy

\(K_{\text {IC}}\)

Fracture toughness

\(Y_I(S/R)\)

The mode-I geometry factor

\(P_{\text {max}}\)

The peak applied load

B

The thickness of the specimen

R

The specimen radius

E

Elastic modulus

\(\nu\)

Poisson’s ratio

\(h_{\text {f}}\)

Height of fracture zone

\(\gamma\)

Unit weight of roof strata

\(A_{\text {m}}\)

Cross section of excavated panel

\(\sigma _{\text {v}}\)

Initial vertical stress

\(\sigma _{\text {c}}\)

Uniaxial compressive strength of roof strata

\(A_{\text {d}}\)

Unit surface of destressed zone

k

Bulking factor of caved materials

MPS

Maximum principal stress

Notes

Acknowledgements

The first author would like to acknowledge the financial support provided by the China Scholarship Council (CSC) under Grant Number 201606420056. The authors would like to thank the anonymous reviewers for their considerable effort in improving the paper.

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Copyright information

© Springer-Verlag GmbH Austria, part of Springer Nature 2018

Authors and Affiliations

  • Xiangjian Dong
    • 1
  • Ali Karrech
    • 1
    Email author
  • Hakan Basarir
    • 1
  • Mohamed Elchalakani
    • 1
  • Abdennour Seibi
    • 2
  1. 1.School of Civil, Environmental and Mining EngineeringThe University of Western AustraliaCrawleyAustralia
  2. 2.Petroleum Engineering DepartmentUniversity of Louisiana at LafayetteLafayetteUSA

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