Ultrasonic Velocities, Acoustic Emission Characteristics and Crack Damage of Basalt and Granite

Abstract

Acoustic emissions (AE), compressional (P), shear (S) wave velocities, and volumetric strain of Etna basalt and Aue granite were measured simultaneously during triaxial compression tests. Deformation-induced AE activity and velocity changes were monitored using twelve P-wave sensors and eight orthogonally polarized S-wave piezoelectric sensors; volumetric strain was measured using two pairs of orthogonal strain gages glued directly to the rock surface. P-wave velocity in basalt is about 3 km/s at atmospheric pressure, but increases by > 50% when the hydrostatic pressure is increased to 120 MPa. In granite samples initial P-wave velocity is 5 km/s and increases with pressure by < 20%. The pressure-induced changes of elastic wave speed indicate dominantly compliant low-aspect ratio pores in both materials, in addition Etna basalt also contains high-aspect ratio voids. In triaxial loading, stress-induced anisotropy of Pwave velocities was significantly higher for basalt than for granite, with vertical velocity components being faster than horizontal velocities. However, with increasing axial load, horizontal velocities show a small increase for basalt but a significant decrease for granite. Using first motion polarity we determined AE source types generated during triaxial loading of the samples. With increasing differential stress AE activity in granite and basalt increased with a significant contribution of tensile events. Close to failure the relative contribution of tensile events and horizontal wave velocities decreased significantly. A concomitant increase of doublecouple events indicating shear, suggests shear cracks linking previously formed tensile cracks.

Acoustic Emission Analysis of Cement Mortar Specimens During Three Point Bending Tests

“…The released elastic wave travels as a spherical wave within the bulk of the material. The detection of AE events is used for damage localization and damage level assessment in brittle materials such as concrete and rocks (Lockner, 1993;Stanchits et al, 2006;Aggelis et al, 2013;Stergiopoulos et al, 2013). The AE events, due to crack growth in brittle materials, are usually observed in the high frequency range, typically between 50 kHz and 800 kHz.…”

Triggering Processes in Rock Fracture

“…We analyzed AE data during loading at a constant displacement rate before peak strength [37][38][39]. We performed a full moment tensor (FMT) inversion of AE data using first-motion P-wave amplitudes [40,41].…”

Ki̇reçtaşlarinin Aşinma Di̇rençleri̇ni̇n Endeks Özelli̇kleri̇ Yardimiyla Beli̇rlenmesi̇

“…1929 yılından itibaren malzemelerin tahribatsız muayeneleri için de kullanılmaktadır. Kayaç içerisinden geçirilen P ve S dalgalarının yayılma hızlarından faydalanılarak çeşitli kaya türlerinin dokusal özellikleri [10], mineral yönlenmesi [11], kırık ve çatlaklar [12], porozite [13], geçirgenlik [14], anizotropi [15], yüzey sertliği [16], yoğunluk, tek eksenli basınç dayanımı ve Young modülü [17] konuları hakkında bir çok çalışma yapılmıştır. Bu çalışmada ultrasonik hız deneyi hava kurusu numuneler üzerinde gerçekleştirilmiştir.…”