Mining Contract: Design of Underground Mine Seals Under Explosive Events

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Contract #	200-2007-22541
Start Date	8/31/2007
End Date	10/31/2009
Research Concept	The objective of this contract is to establish guidelines for mine seal design under static and dynamic loading conditions from gas and/or dust explosions within sealed areas. Research to establish these guidelines will focus on three main tasks: Parametric studies using three-dimensional numerical models: These engineering studies will consider all factors that enter into seal design, including design pressure-time curves, construction materials and methods, seal dimensions, foundation conditions, and convergence loading. Calibrating engineering models to NIOSH Lake Lynn Experimental Mine test data: Structural data collected from tests at NIOSH will be analyzed to define the failure criteria for various seal structures and to calibrate the computer models. Inspection and monitoring of underground mine seals for model validation: Project researchers will make selected mine tours to inspect various seal types, observe failure modes, examine foundation conditions, and assess leakage through seals. Researchers will install instrumentation at select seals to measure roof-to-floor convergence and the corresponding load increase on seals.
Topic Areas	Explosion Prevention

Contract Status & Impact

This contract is complete. To receive a copy of the final report, send a request to mining@cdc.gov.

Project work focused on design of the reinforced concrete (RC) seal. Finite element modeling was used to simulate the RC seal subjected to dynamic loading. Abaqus/Explicit® (version 6.6) was selected to conduct this simulation because of its capability to simulate cracking and failure of RC structures. Three concrete material models representing a wide spectrum of concrete behavior in the tensile and compressive post-peak range were investigated. The post-peak behavior of concrete material in tension and compression proved to be the dominating factor in the response of RC seal subjected to explosion pressure.

A constitutive model for concrete developed by Barth and Wu was used to simulate the RC seal under an instantaneous explosion of 120 psi. This model was chosen because it has been verified and has a complete input dataset for use with Abaqus® models. The effect of the following parameters on the stability of the RC seal subjected to explosion loading was studied:

vertical rebar size,
vertical rebar spacing,
horizontal rebar spacing, and
seal thickness and height.

This parametric study was used to optimize important parameters for seal design. Rebar size, rebar spacing, and seal thickness have varying degrees of influence on seal stability. Seal thickness is most important followed by rebar spacing. Rebar size has limited influence because the axial force developed in the rebar is well below the rebar yield limit.

Research under this project has resulted in the following publications:

Effect of Roof Convergence on Stability of Underground Mine Seal Subjected to Explosion loading - Numerical Approach
R. Kallu, S.S. Peng, D. Turner, K. Morsy, Proceedings of the 26th ICGCM, Morgantown, WV, August 2006, 370-378.
Numerical Simulation of Reinforced Concrete Mine Seal Subjected to Explosion Loading
K. Morsy, A. Yassien, R. Kallu, and S. S. Peng, Proceedings of the 27th ICGCM, Morgantown, WV, July 2008, 180-188.
Design of Mine Seals to Meet New MSHA Standards - progress report
S.S. Peng, K. Morsy, A. Yassien, and R. Kallu. Presentation at the MINExpo 2008, Las Vegas, NV, September 23, 2008.
Cementitious Seal/Rock Interface Under Hydrostatic and Dynamic Loadings
Khaled M. Mohamed, Asmaa Yassien, R. Reddy Kallu, and Syd S. Peng. Proceedings of the 28th ICGCM, Morgantown, WV, July 2009.
Design of Reinforced Concrete Seals for Underground Coal Mines
R. Reddy Kallu, Ph.D. Dissertation submitted to West Virginia University, Morgantown, WV, 2009.
Analysis and Design of Reinforced Concrete and Cementitious Seals
Syd S. Peng, Asmaa Yassien, Khaled M. Mohamed and R. Reddy Kallu. Final Report submitted to NIOSH on Contract Number 200-2007-22541, November 2009.