Defense
Student: Paula Rayane Lopes de Andrade
Program: Geophysics
Title: "Characterization of ornamental rock blocks by waveforms: ultrasonic, seismic and numerical modeling"
Advisor: Prof. Dr. Carlos Alberto Mendonça
Judging Comitee:
- Prof. Dr. Carlos Alberto Mendonça - Presidente e Orientador - IAG/USP
- Prof. Dr. Carlos Alberto Moreno Chaves - IAG/USP
- Prof. Dr. José Agnelo Soares - UFCG (por videoconferência)
- Profa. Dra. Graça Fátima Moreira Vasconcelos - UMinho, Portugal (por videoconferência)
- Prof. Dr. Giorgio Francesco Cesare de Tomi - EP/USP (por videoconferência)
Other Members:
- Profa. Dra. Liliana Alcazar Diogo - IAG/USP
- Profa. Dra. Elissandra Nascimento de Moura Lima - UFCG
- Dr. André Luis Ferreira da Silva - EP/USP
- Dr. Alberto Barontini - Unich, Itália
- Prof. Dr. Francisco Pinheiro Lima Filho - UFRN
Abstract:
Rock extraction for construction and ornamental purposes requires evaluation methods capable of predicting block quality, minimizing waste generation, and promoting greater sustainability in mining activities. The prior identification of internal structures, altered zones, and discontinuities is essential for estimating the value of a block before processing or export. Methods widely used at the quarry-face scale, such as seismic refraction, are not directly applicable to blocks of variable dimensions, since the existence of a refracting horizon is not guaranteed. In addition, tomographic approaches and analyses based exclusively on travel times may present limited resolution for small-scale features, partly due to finite-frequency effects such as wavefront healing. In this work, non-destructive evaluation methodologies based on waveform analysis were developed as a complement to traditional ultrasonic pulse velocity tests, integrating the Wavefront Transmission Test (WTT), the Wavefront Symmetry Test (WST), and numerical modeling with Full Waveform Inversion (FWI). Numerical simulations and experimental tests in quarries showed that waveform-based evaluations, such as the WTT, are sensitive to subtle internal changes that may remain undetected in visual inspections or in analyses restricted to the travel time of transmitted waves. The WST, in turn, assigns spatial meaning, at the bench scale, to properties measured at discrete points, delimiting regions where wavefield symmetry is preserved and highlighting zones with probable structural degradation. FWI simulations proved promising for the identification and characterization of internal structures, even with a reduced source–receiver configuration, reinforcing the potential of combining numerical and experimental methods as an interpretation tool. In block tests using the WTT, waveform analysis showed greater sensitivity than Ultrasonic Pulse Volocity UPV in discriminating internal heterogeneities. A correlation index ranging was proposed to quantify the invariance of the transmitted pulse waveform. Higher-quality blocks presented correlation values between 0.86 and 0.88, whereas lower-quality blocks showed values between 0.17 and 0.32, highlighting the potential of the proposed parameter for the classification of representative blocks from quarries in Northeastern Brazil. The results obtained with the WST indicate that the method can be implemented with simple instrumentation, such as a single-channel seismometer and a Schmidt hammer as the seismic source, favoring its application in small quarries with limited technical and economic resources.
Keywords: Ornamental rocks , Full Waveform Inversion (FWI), Waveforms