Abstract
ABSTRACT In this study, discrete physical models using different blocks and hole sizes, and backfill characteristics are used to simulate changing underground mine conditions due to mining activities. In addition to voids and various backfills, this study includes fractures to investigate their effect on seismic wave propagation. The fracture systems in concrete blocks with sizes of 150 mm, 225 mm, 300 mm, 375 mm, and 450 mm were created by filling holes of various diameters in the concrete cubes with a static cracking agent (SCA). This process mimicked blast and stress-induced fracturing in the underground mine environment. AE measurements indicate that AE signal attenuation from fractures is more severe than due to backfill and in presence of fractures, backfill did not create a favorable environment for AE wave propagation toward receivers. AE signal arrival time to receivers mainly depends on the direction of AE wave propagation rather than the geometrical arrangement of the sensors in the presence of the voids, backfills, and fractures. AE signal arrivals to receivers are governed by the subsurface variability, Snell's law, and AE wave propagation direction. These factors should be considered to enhance the current source location approaches in microseismic monitoring systems. INTRODUCTION A major concern in deep underground mines is seismicity and rockburst of which frequency increases with mining depth. These phenomena significantly influence mine safety, productivity, and operating costs. Considering the undesirable impacts and consequences of seismic activities and rockbursts, their forecasting and control play a critical role in deep underground mines. Seismically active mines rely on microseismic monitoring systems to predict microseismic events and to minimize the exposure of personnel and equipment to seismic hazards. The microseismic monitoring system is able to identify, locate and quantify the mine seismicity enabling a better understanding of the rockburst mechanism.