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Tectonic strain in salt rock mass based on measurements

Szczerbowski Zbigniew, Niedbalski Zbigniew, Bednarek Łukasz

Geology, Geophysics and Environment

2023

Vol. 49, no. 2

157--173

The measurement method with the application of an extensometer for the detection of the manifestation of tectonic strain is presented in this paper. The instrument is operated in underground construction for engineering purposes, and the authors applied it in a deeply placed underground old mine gallery in the Bochnia Salt Mine, just at the tectonic boundary of the Outer Carpathians which is commonly considered to be a tectonically active zone. The presented study is characterized by two basic features. The first is the placement of the measurements deep in an old mine which is an environment free of atmospheric factors disturbing the detection of a tectonic signal. The second is a combination of routine measurements carried out for engineering purposes and research measurements enabling the extension of the observation of displacements in the space outside underground workings, inside the rock mass that has been penetrated by extensometer probes. The extensometric measurements have been made using three 7-meter long sections. The results showed the differentiation in the displacement rates of points placed in the side walls: in the southern profile, the annual displacements are approximately 1.5 mm and in the northern one – approximately 1 mm. The combined result corresponds to the amount of the annual convergence value which has been determined by the classical surveys in the excavation where extensometric measurements have been made. What is more, the ongoing displacements in the southern side wall involve the entire part of the rock mass which is penetrated by an extensometric probe, but the displacements in the northern side are only observed in the first 2 m of the penetrated part of the rock mass. This differentiation is interpreted by the authors as being the result of tectonic strain acting from the south exerted by the Carpathians.

Determining of model similarity for flexspline of harmonic drive with the use of FEM and extensometer method

Budzik G., Kozik B., Pacana J.

Journal of KONES

2009

Vol. 16, No. 2

55-60

This paper presents an analysis of the feasibility of using the model similarity method in engineering design. The analysis applies to virtual and physical models of the flexspline body of harmonic gear drive. The task consisted in determining stress distribution in the virtual models of the flexspline by means of the finite element method (FEM) and next its verification during bench tests by the extensometer method. The values of stresses calculated by the FEM method and the extensometer method were compared with each other with the aim ofdefming model similarity. The numerical calculations were made by means of the ADINA application which uses FEM with the use of contact elements. Stress distribution calculations applied to simplified virtual models of the flexspline. By the simplification of models a great number of finite elements used for the discretisation process were limited and because of that the time of calculations was shortened. The simplified model was precise enough to determine the stresses in the flexspline body. The subject of this analysis was the impact of different values of the torque moment T2 on the stresses in the flexspline body of the harmonie drive. The results of numerical calculations were checked against the standing tests of the real drive by applying the extensometer method. During the work of the gear, the values of relative elongation were measured and, based on them, the values of stresses were determined and compared to the results of the numerical calculations by FEM in the analogous cross-sections of the flexspline. The comparability of the results received by both methods proves both that the models used in the numerical calculations were properly designed and that the assumptions as well as the calculation were properly made. The determining of model similarity for the examined harmonie drive will make it possible to carry out analyses of stress calculations by FEM on virtual models without the necessity to verify them by laboratory standing tests each time.