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Impact of mining induced continuous rockmass degradation on seismic wave velocity

rockburst, seismicity, mining, acoustic emission

5^th International Symposium on Mine Safety Science and Engineering

Katowice, Poland – November 21-25, 2021



Impact of mining induced continuous rockmass degradation on seismic wave velocity

Zarina Mukhamedyarova^1,*and Fidelis Suorineni<sup>2

1</sup>School of Mining and Geosciences, Nazarbayev University, Nur-Sultan, Kazakhstan

²School of Mining and Geosciences, Nazarbayev University, Nur-Sultan, Kazakhstan

*corresponding author: Tel +77719059999 email: zarina.mukhamedyarova@nu.edu.kz



ABSTRACT



Seismicity is the phenomenon that occurs naturally by earthquake activity or unnaturally by induced earth vibrations from men–made activity. The study focuses on seismicity in underground mining caused by human activity. Despite technological progress, the estimate of the rockburst is still a controversial and debatable technique in the mining industry. The accuracy and prediction of the microseismic monitoring system depend on the input velocity in the event source location.



To understand changes in wave velocity, laboratory tests with mimic models in a controlled environment were conducted. Mimic models with holes have been filled with various mixtures of sand, cement, and water at changing ratios to represent different backfilling at different extraction stages. Acoustic Emission(AE) tests with eight sensors and known source locations were conducted to measure wave arrival time for P wave velocity calculation.  Uniaxial compression tests were carried out to determine the rock mass quality of mimic models and backfills.



Rock samples from concrete and granite represent scaled underground mine models. Sample material choice is based on rock homogeneity. Sample sizes vary between size 150 mm and 450mm cubes to consider the effect of boundary conditions, and each sample size is with and without hole to represent increasing mine with time.  Each hole is in the center and through the sample, hole diameters vary between 50 mm and 100 mm to represent a mine with an increasing extraction ratio. Mining-induced fractures were simulated by a static cracking agent. The damage extent in the rock sample was determined through RMR system. Fractures in the rock samples represent joints in real mines. Apart from AE tests with intact rock samples and samples with empty holes, each cube size was tested with different backfill types including dry sand, wet sand, 5%, 10%,15%, and 20% cement cured for 8hours-28 days to see the backfill cement ratio and time effect on seismic wave velocity. The highest P wave velocity stands for intact rock samples and the samples with empty holes. The lowest P-wave velocity was measured when the samples were filled with 20% cement backfill cured for 28 days. The test results showed the effect of voids, fracture intensity, and different backfill types on wave velocity.















Acknowledgment

This project is financially supported by the Collaborative Research Project of the Provost Office of Nazarbayev University. The authors are grateful for their support.