Internal mechanical losses in rocks of different genesis

Description

The purpose of the study was to determine the mechanical loss coefficient Q-1 in rock samples of different genesis: sedimentary (limestone, dolomite), metamorphic (marble), magmatic (gabbro), and the dependence of this coefficient on frequency in the range from 0.003 to 0.1 Hz. This frequency range manifests itself in the form of seismic vibrations of the soil during earthquakes. They can lead to the destruction of buildings and other structures. Beam specimens with a width of 40 mm, height of 40 mm and length of 150 mm were used for testing. The ASIS test complex (NPO Geotek LLC, Penza, Russia) was the test basis. The test of the specimens used three-point scheme by the International Society for Rock Mechanics (ISRM) recommendations. The test device allows the minimisation of friction in the nodes of the setup. The ASIS software made it possible to set up a cyclic testing program with an indication of the number of cycles, the maximum and minimum deformations of the testing machine frame, and the speed of movements, with their increase and decrease. Two LVDT displacement transducers with a measure range of 10 mm registered deflection directly on the specimen. These converters had a connection to an 18-bit ADC of the QMBox measuring system (R-Technology, Moscow, Russia). The measuring system recorded the parameters, i.e., the resulting load on the sample, and the specimen deflection at the midpoint during deformation. The frame movement and the specimen deflection did not coincide with each other. Therefore, we took into consideration the displacements measured directly on the sample. The data set contains Q-1 test results for a few beam specimens, as well as the loss factors measured by hysteresis loop method. Frequency dependences and approximations of the Rayleigh attenuation model are also provided.

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