| Abstrakt: |
Natural coal is one of the main energy sources in common use. The development of coal resources is easy to produce a large number of waste water and other wastes, and then cause environmental pollution. The characteristics of coal seam porosity and permeability are directly related to the effect of coal mining and environmental protection. Acoustic technology has been gradually applied to reservoir evaluation of oil, gas and coal resources. To explore the correlations between the acoustic velocity of coal and its mechanical-physical properties, we designed a core holder to conduct wave velocity and seepage parameter measurements with effective stress variation. These measurements, combined with computed tomography (CT) scanning results, were analyzed to identify the influence of native coal bedding structure, sample density, and loading stress. The results show that the acoustic velocity of coal has a strong relationship with the test direction (coal bedding structure), sample density and sample strength; both the longitudinal wave (P-wave) and transverse wave (S-wave) velocities increased with the sample density and strength. The P-wave and S-wave velocities are much higher parallel to the bedding planes than they are perpendicular to the bedding planes; parallel to the bedding planes, the velocity along the strike direction is more significant than that in the inclination direction. The S-wave is much more easily influenced by the bedding structure than the P-wave is. Additionally, the P-wave velocity increases significantly with increasing confining pressure, while the permeability and porosity decrease with increasing confining pressure exponentially. The acoustic velocity and porosity are negatively linearly correlated, while velocity and permeability have a negative nonlinear correlation. Visualization of the coal structure indicated that the observations of the dynamic closing of internal cracks and pores in the coal agrees well with the acoustic and seepage test results. [ABSTRACT FROM AUTHOR] |
