Analysis of floor stability in underground coal mines
This research work presents a rock mass strength criterion for mine floor strata based on the empirical method proposed by Hoek and Brown. This method was modified by the author with the introduction of the concept of the point of critical energy release, the inclusion of tensile strength and the adoption of alithostatic state of stress in rock masses. Its application requires the determination of RMR (rock mass rating) of the Geomechanics Classification. Equivalent values of cohesion and the angle of internal friction are calculated and finally the ultimate stress on the floor layers is determined. An alternative solution employing the limit analysis approach is also presented. A step by step procedure for the design of mine floors is proposed, containing guidelines for the necessary field and laboratory investigations and the establishment of the bearing capacity of floor strata. A practical example, accompanied by a microcomputer program and the code, is also included. Nine case histories have been included for the verification of the developed criterion, both in longwall and room and pillar mining. Numerical modeling was used to analyze the stress distribution and displacements in the headgate entries of two longwall panels, considering both an elastic solution and the time-dependent behavior of the rock. It was concluded that with the current knowledge of rock mechanics the solution of floor stability problems has to rely on empirical methods. Due to the time-dependent nature of floor rocks a long term strength ought to be considered, and thus the point of critical energy release becomes an essential property to be determined during the phase of geotechnical investigations.
- Research Organization:
- Pennsylvania State Univ., University Park, PA (USA)
- OSTI ID:
- 7054296
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
012031* -- Coal
Lignite
& Peat-- Underground Mining-- Strata Mechanics & Control-- (1987-)
CALCULATION METHODS
COAL MINING
COMPUTER CODES
COMPUTER-AIDED DESIGN
DESIGN
FLOORS
FRICTION FACTOR
LONGWALL MINING
MATHEMATICAL MODELS
MECHANICAL PROPERTIES
MECHANICS
MINING
ROCK MECHANICS
ROOM AND PILLAR MINING
STABILITY
STRATA CONTROL
STRESS ANALYSIS
TENSILE PROPERTIES
TIME DEPENDENCE
UNDERGROUND MINING