Sonic test singularities of granite stone masonries

Abstract

For the non-destructive characterization of structures composed of granite stone masonry (heterogeneous materials), in this case of double sheet, one of the most suitable test options is the use of sonic tests. Through these sonic tests, it is possible to estimate the propagation velocities of the P, R and S waves. With these velocity values, it is possible to estimate the elastic parameters that characterize the material. Data acquisition requires special attention because during these tests there are factors that may significantly influence the signal, such as the possible recording of two momentary impacts of the hammer, bad coupling of the recording transducers and environmental noise, which can compromise the quality of the signals, and the literature this topic was not suficciently adressed. It is noteworthy that the estimation of the propagation time of waves and their propagation trajectories are not trivial, since it has great complexity in obtaining the value of the wave's arrival time being its automation a non-strait forward and not reliable process that should be carried out by an experienced user, especially for granite masonries. It is also necessary to identify which types of waves are being measured and represented by these signals, whether P, R or S. However, the identification of waves depends on the intrinsic characteristics of each one of them and on the type of test configuration to be performed. Thus, this work aims to present the advances obtained in the use of sonic tests, considering different configurations, in order to assist in the characterization of structures composed of granite stone masonry. In addition, to proposing new sonic data analysis and processing methodologies to improve the accuracy and reliability of the results obtained in this type of non-destructive test. For this, 8 samples of double sheet granite masonry walls were built in a controlled environment and sonic tests (direct, indirect and unconventional configuration) were performed to characterize these traditional masonries. The results of sonic tests are promising and novel, especially considering that the applicability of these tests on masonry walls is a research area that is not yet sufficiently consolidated, in addition to the difficulties inherent in the fact that the materials are not homogeneous and isotropic. The results showed great variations due to the heterogeneity of the panels. The velocity variation from for the first receiver was higher (1584 m/s) than the other receivers because the first trajectory has less interference from the vertical joints along the wave trajectory. For both tests (direct and indirect), a sensitivity study on the variation of these velocities as a function of the djdT ratio was presented to quantify the estimated velocity for these paths. As expected, the higher this relationship, the lower the velocity values, due to interference from wave attenuation in the horizontal joints. The non-conventional sonic tests proposed in this paper for adequate conditions to obtain the S waves by changing the position and orientation of the receivers and in the direction of impacts (with the aid of an 90° angle fixed to the structure) was adequated demonstrated: it is concluded that the waves interpreted as S reached mean velocity of 1500 m/s, without joint interference. To corroborate the results obtained by the sonic tests, ultrasonic tests were also carried out. The tests confirmed the wave propagation velocity values in the crossblock around 3700 m/s, and with the presence of a joint in the trajectory, the velocities are around 1000 m/s.