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Instability Mechanism and Control Countermeasure of a Cataclastic Roadway Regenerated Roof in the Extraction of the Remaining Mineral Resources: A Case Study

  • Wenqiang Ma
  • Tongxu Wang
Original Paper
  • 48 Downloads

Abstract

Most accessible mineral deposits are nearly exhausted. Consequently, some resources that were previously abandoned are now being considered for remining. This paper describes a case study that aims at revealing the instability mechanism and selecting the optimal control countermeasures for a cataclastic roadway regenerated roof (CRRR) during the extraction of the remaining mineral resources. Based on the structural model of a cataclastic regenerated roof (CRR) of a remaining lower slice, a modified natural arch mechanical model for a CRRR was established by considering the lateral pressure and stress concentration coefficient of the bearing arch, through which the modified bearing arch curve equation and arch rise expression were deduced. The relationship between the modified arch rise and the lateral stress was obtained through a practical case. Next, a numerical model of a CRRR, which accounted for the cataclastic features, was built in the Universal Distinct Element Code (UDEC). The development of subsidence and fractures in the roadway roof was determined through modeling under various roof support scenarios, namely no support, rock bolt (RB) support, rock bolt and cable (RBC) support and a combined support of the rock bolt, cable and steel beam (RBCS). The theoretical analysis, numerical simulation and monitoring results of the RB and RBC stress all indicated that a bearing arch existed in the CRRR and that the arch rise underwent changes during the roof hanging time and with different support scenarios. The support structure should exceed the bearing arch rise in height and should be leak proof to avoid roof leakage. After a comparative analysis of the numerical and field support effects provided by various supporting scenarios, the RBCS support scenario was shown to be the optimal roof support choice, providing a good controlling effect for a CRRR and meeting the production requirements.

Keywords

Cataclastic roadway regenerated roof Remining Instability mechanism Control countermeasure 

List of Symbols

\({k}_{\rho }\)

Broken expansion coefficient of caved rocks

\({H}_{\rm c}\)

Mining height

\({H}_{\rm m}\)

Roof caving height

\({H}_{\rm a}\)

Irregular caving sub-zone height

\({H}_{\rm b}\)

Regular caving sub-zone height

\(K_{\rho }^{\prime }\)

Residual broken expansion coefficient

\({H}_{\rm r}\)

Caving zone height after compaction

\(H_{{\text{a}}}^{\prime }\)

Irregular caving zone height after compaction

\(H_{{\text{b}}}^{\prime }\)

Regular caving sub-zone height after compaction

\({H}_{\rm s}\)

Sinking height of main roof

\(n\)

Total rock layer number in main roof

\({H}_{\rm f}\)

Water-conductive fissure zone height

L1, L2, L3, L4

Serial number of each rock layer in main roof from bottom to top

\(\sum M={H}_{\rm c}\)

Mining height

\({L}_{0}\)

Initial fracture span of rock layer in main roof

\({\sigma }_{x}\)

Tensile strength

\({M}_{\rm c}\)

Thickness of the follow-up layer

\(\alpha\)

Dip angle of rock layer

Z1, Z2, Z3

Regenerated zone after cementation, weakly cemented compaction zone, fractured zone

γ

Average volume weight of rock strata

H

Depth below surface

λ

Lateral pressure coefficient

q

Uniformly distributed load

2a

Roadway width

P

Lateral stress acting on the arch

T

Horizontal thrust from the right arch

W

Thrust along the arch tangential direction

F

Friction force

N

Reaction force

fj

Rock consolidating coefficient

T1

Horizontal thrust at point A

η

Safety factor

c

Vertical semiaxis length of the ellipse

\(c\sqrt{\mu }\)

Horizontal semiaxis length

b

Arch rise of the modified bearing arch

Notes

Acknowledgements

This research is financially supported by the Science and Technology Project of Henan Province (Grant no. 182102310786), the Nanhu Scholars Program of Xinyang Normal University and the Natural Science Foundation of China (Grant no. 41807240). The author gratefully acknowledges the financial support provided by them.

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Copyright information

© Springer-Verlag GmbH Austria, part of Springer Nature 2019

Authors and Affiliations

  1. 1.College of Architecture and Civil EngineeringXinyang Normal UniversityXinyangChina
  2. 2.State Key Laboratory of Mining Disaster Prevention and Control Co-founded by Shandong Province and the Ministry of Science and TechnologyShandong University of Science and TechnologyQingdaoChina

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