A study on ultrasonic wave propagation across fractures in jointed rocks

The effect of joints on wave propagation in rocks has always been a matter of concern with regard to their transmission and attenuation characteristics. Experimental studies are conducted to analyze the wave attenuation characteristics in single and parallel fractures at varying angles considering non welded interfaces in rocks. After validation with the ultrasonic pulse velocity tests, numerical models using UDEC were developed to simulate the wave propagation in jointed rocks. The numerical study was extended for multiple fractures over a range of ultra sonic frequencies. The effect of the fracture angle and number of cracks on the transmitted P wave velocity and corresponding travel time ratio were investigated. This study was conducted on blocks of artificially prepared rock specimens casted with gypsum plaster, introducing artificial joints at various angles. The variation in P wave velocity and travel time ratio for different joint angles and multiple joints have been studied.