Mechanical Behavior of Coal Specimen under Pore Gas Pressure

Abstract

To investigate the mechanical behavior of coal specimens with the pore gas pressure, the following laboratory experiments on coal collected from Ashibestu and Akabira Coal Mine were conducted; the triaxial compression tests and those with the pore gas pressure by useing the triaxial testing machine under the condition of the strain rate of 1.3×10^-4/sec and confining pressure and pore gas pressure extending up to 40MPa, the gas permeability tests under the hydrostatic pressure by means of the transient pulse method.
The experiments showed that coal strength increased and brittle behavior became predominant with the increase of the effective confining pressure. The law of effective stress for the fracture criterion was valid for coal specimens whose pore were fully saturated with gas pressure.
As the experimental results, the coal specimens were more permeable under the low hydrostatic pressure than under the high hydrostatic pressure, and these phenomena and deformation were largely concerned with the collapse processes of cracks in a coal specimen under the hydrostatic pressure.